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A 420 Reflection on How Cannabis Changed While We Weren’t Looking

A 420 Reflection on How Cannabis Changed While We Weren't Looking
The Weed Was Different Back Then — A 420 Reflection on How Cannabis Changed While We Weren't Looking | The Certified
The Grower's Connect
Cannabis Culture · 420 Special · April 2025

The Weed Was Different Back Then — A 420 Reflection on How Cannabis Changed While We Weren't Looking

Six people. Half a gram. A gravity bong made from a two-litre bottle. And everyone was done for the night. Something has changed — and it's worth asking what, and why, and whether we've gained more than we've lost.

The Stoners Corner  ·  April 2025  ·  420 Special
Decades of South African cannabis culture
½g Six people. One gravity bong. Done.
2018 ConCourt ruling that changed everything
Listen to this article The Weed Was Different Back Then — A 420 Reflection

Happy 420 to everyone in the South African cannabis community. If you've been following this series, you know we've spent the last several weeks going deep into the plant science — protoplasts and phytomers, endocannabinoid systems and anandamide, sucrose infusion and receptor pharmacology. Today we put the textbooks down. Today is for the culture.

And because this is 420, and because reflection is what the day deserves, I want to talk about something that almost every long-time cannabis user in South Africa has said at some point — usually while sitting with friends, usually while passing something around — and usually with a slightly distant look in their eyes.

The weed was different back then.

Not better in every way. Not worse in every way. Just different in a way that matters, and in a way that the science we've been covering actually helps explain. So let's honour it properly — the memory, the culture, the change, and where we might be going next.

What We Remember

There was a time in South Africa when good weed was called Swazi, or Malawi, or Durban Poison. It came pressed into bricks sometimes, other times in those hand-rolled bundles wrapped in newspaper that you'd unfold carefully on the kitchen table. The smell was something else entirely — a deep, almost-funky, hay-and-earth-and-something-sharp smell that filled a room in seconds.

You could smell a person walking past with a bag of it. Not a hint of it. The whole thing. On the street.

There was a time when six friends would sit around a gravity bong — a two-litre bottle with a hole cut in the bottom, a cone made from tinfoil or a stripped socket head, submerged in a bucket of water — and half a gram of high grade would floor every single one of them. Not mildly high. Not pleasantly buzzed. Done. Couch-locked, laughing too hard to speak, raiding the kitchen, arguing about something from three topics ago.

The pipes were homemade. The papers were whatever brand was at the corner store. Nobody knew the strain name. Nobody knew the THC percentage. Nobody had a terpene profile. You knew if it was green or brown, sticky or dry, smelled right or smelled like it had been sitting in a bakkie for six months. That was the extent of the analysis. And it hit hard. Differently hard. A specific kind of hard that most people who started smoking in the last decade have simply never experienced.

What We Have Now

Fast forward to April 2025. Walk into a compliant dispensary in Cape Town or Johannesburg. Or open an app. Or talk to your grower.

You will be presented with options. Cultivar names, THC percentages printed on labels, terpene breakdowns, CBD ratios, cultivation method declarations, harvest dates. You will be offered Blue Dream or Wedding Cake or Gorilla Glue or something with a name that sounds like it was generated by an algorithm fed exclusively on dessert menus and action movies. You will smell something — often something extraordinary, genuinely complex, citrus and fuel and pine and something you can't name but that your brain files as good.

You will get high. Often quite high. Sometimes very high, if the THC percentage is what the label says and you've respected it accordingly. But here is the thing that almost everyone who has been in this community for more than fifteen years will tell you, usually quietly, usually with a slight shrug:

"It doesn't feel the same. You feel it. You feel good. But something is missing that you can't quite name. It's a sunshine buzz where there used to be a thunderstorm."

Then — The Old School

  • Swazi, Malawi, Durban Poison landraces
  • Newspaper bundles, pressed bricks
  • Gravity bongs, homemade pipes, whatever worked
  • No strain names. No labels. No percentages.
  • Smell that announced itself from across the street
  • Half a gram between six — everyone wrecked
  • A thunderstorm of an experience
  • Rich, complex, deep — and no one knew why

Now — The New Era

  • Hundreds of named cultivars, curated genetics
  • Labels, lab tests, terpene profiles
  • Vaporisers, bongs, dab rigs, pre-rolls
  • THC percentages up to 30%+
  • Complex aromas — citrus, fuel, pine, dessert
  • You get high, sometimes very high
  • A sunshine buzz — pleasant, functional
  • More information, sometimes less experience

The Science of Why It Felt Different

We've spent weeks on this platform going deep into plant science and the endocannabinoid system, so let's use that understanding here — because it actually explains a lot of what people are experiencing.

The Old Weed Was Landrace — and That Matters Enormously

Durban Poison. Swazi Gold. These were varieties that had evolved over centuries in specific African climates, producing cannabinoid and terpene profiles that were the result of genuine natural selection rather than commercial breeding objectives. They weren't the highest THC strains in absolute percentage terms — but they were complete in a way that modern strains often aren't.

Modern Breeding Has Chased One Number

Over the past three decades, the commercial cannabis market has selected almost exclusively for one metric: THC percentage. The logic was simple — consumers thought higher THC meant stronger, higher THC numbers sold better, so breeders bred for THC, generation after generation, optimising for one compound at the expense of dozens of others.

What Got Bred Out — And Why It Mattered

  • Terpenes. That old Durban Poison smell you could detect from across the street wasn't just aroma — those terpenes were doing pharmacological work, modulating how THC crossed the blood-brain barrier and binding to their own receptors. They were contributing to the specific character of the experience.
  • CBD. For a long time, high CBD was considered a flaw — it was seen as diluting the THC effect. Modern research tells us CBD modulates the CB1 receptor response to THC, preventing overwhelming receptor saturation and contributing to a more sustained, textured experience. Many old strains had more CBD than anyone knew.
  • Minor cannabinoids. CBG, CBN, CBC, and dozens of others were present in landrace varieties in profiles shaped by centuries of natural selection. Commercial breeding for THC has reduced their presence significantly.
  • The entourage effect. The synergistic interaction between all cannabis compounds was not understood, not measured, and not cultivated for. The old cannabis had it by accident of nature. Much modern cannabis has been stripped of it by design.

And Then There Is Tolerance

The endocannabinoid research we've covered in this series explains this directly. When you first smoke cannabis — as most of the people who remember the old South African weed did, in their teenage years — your CB1 receptors have never been exposed to exogenous cannabinoids. Your endocannabinoid system is at full sensitivity. The impact of THC binding to those fresh, undesensitised receptors is dramatically different from the impact on a receptor system that has been regularly stimulated for fifteen or twenty years.

The thunderstorm was partly the thunderstorm. It was also partly being nineteen years old with a virgin endocannabinoid system sitting in a township kitchen with five friends and half a gram of Swazi that smelled like the earth itself.

And the Delivery Method Was Violent

A gravity bong is not subtle. It delivers a large, dense, concentrated mass of smoke in a single forced inhalation that bypasses every natural hesitation. The modern trend toward joints, vaporisers, and careful measured hits is more sophisticated — but it is also fundamentally less aggressive in its delivery. The bucket bong was an assault. A well-rolled joint is a conversation.

The Real Answer

The old weed felt the way it did because of a combination of factors: richer terpene profiles, more balanced cannabinoid ratios including natural CBD, genuinely novel CB1 receptor exposure, and a delivery mechanism designed for maximum impact. It was not simply "more potent" — it was more complete. And your nervous system had never experienced anything like it.

What We Gained

It would be dishonest to make this only a nostalgia piece. The gains are real and substantial.

The knowledge is real. We understand now what we had no idea about then. We know about terpenes and cannabinoids and the entourage effect and CB1 receptor density and the endocannabinoid system. The series on this platform over the past months is evidence of that — a grower today has access to scientific understanding that would have been unimaginable twenty years ago.

The cultivation is real. The genetics, growing techniques, environmental controls, nutrient science, and harvest timing that define modern cannabis production represent decades of accumulated knowledge. Plants are healthier, yields are more consistent, contamination is lower, and the quality ceiling is higher than it has ever been.

The legal landscape is shifting. The Constitutional Court's 2018 ruling decriminalising private use and cultivation was a watershed moment for South African cannabis culture. The conversations happening in dispensaries, at cannabis events, in online communities, in research departments at South African universities — none of that existed in the era of the gravity bong and the newspaper-wrapped Swazi.

The community is openly itself. The South African cannabis community has always been extraordinary — creative, resilient, deeply knowledgeable in its own way, and characterised by a generosity of spirit that the culture seems to produce wherever cannabis takes root. The difference is that today it can exist in the open. The events happening around the country this April are evidence of a community that survived decades of criminalisation and emerged with its culture not just intact but thriving.

What We Lost — And What We Might Get Back

The nostalgia for the old weed deserves to be taken seriously rather than dismissed as rose-tinted memory. What it is pointing to, even if the person feeling it can't articulate it, is the entourage effect. The complete plant. The terpene-rich, cannabinoid-diverse, naturally evolved expression of cannabis that the market has systematically bred away from in the pursuit of THC percentages.

The good news is that some growers know this and are working against the grain. The resurgence of interest in landrace genetics — including South African landraces like Durban Poison, which is one of the most genetically distinctive cannabis varieties on the planet — is partly driven by exactly this recognition. The emerging market for full-spectrum products, live resin, and whole-plant extracts reflects an industry beginning to understand that THC percentage is not the whole story.

"The weed of the future might, in the most important ways, look a lot like the weed of the past — grown with the knowledge of the present, for the experience we remember."

We have more information than we have ever had. We have better growing knowledge than we have ever had. The missing ingredient might simply be the willingness to grow for complexity rather than for numbers — to value a rich, balanced, terpene-forward experience over a 30% THC figure on a label. The weed of the future might, in the most important ways, look a lot like the weed of the past.

4:20 Happy 420 — South Africa — April 2025

To every person who has been part of this community — whether that's decades or days. To the people who shared their last gram. To the gravity bong engineers and the tinfoil artists. To the growers who kept the genetics alive through years when it was genuinely risky to do so. To the activists, the patients, the scientists, and the curious. The weed has changed. So have we. And the conversation we're having now is one this community has always deserved.

The Certified — The Stoners Corner  ·  thecertified.co.za  ·  Happy 420
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What Fibromyalgia Reveals About the Endocannabinoid System and Why It Matters

endocannabinoids
When the System Breaks — What Fibromyalgia Reveals About the Endocannabinoid System | The Certified
The Grower's Connect
ECS Series · Part 3

Continuing the endocannabinoid system series. Previously: Anandamide — Unlocking the Bliss Molecule and Your Body Makes Its Own Cannabis — And Running Is the Key That Unlocks It. This week: what happens when the system breaks.

The Endocannabinoid System · Part 3 · Clinical Deficiency

When the System Breaks — What Fibromyalgia Reveals About the Endocannabinoid System and Why It Matters

A 2025 peer-reviewed review has mapped the relationship between fibromyalgia and the endocannabinoid system in detail. The findings suggest that what millions experience as widespread chronic pain may be, at least in part, a disease of endocannabinoid deficiency.

The Grower's Connect  ·  2025  ·  11 min read
6.4% of US adults affected by fibromyalgia
94% of patients reported pain relief with cannabis
35% Reduction in opioid use when combined with cannabis
Listen to this article When the System Breaks — What Fibromyalgia Reveals About the Endocannabinoid System

Over the past two weeks we have been building a picture of the endocannabinoid system from the inside out. We looked at anandamide — the bliss molecule — what it is, where it comes from, and what it does in the brain and body. Then we looked at what happens when you run at the right intensity, and how moderate exercise triggers your body's own endocannabinoid release — reducing anxiety, elevating mood, and producing effects that closely mirror what cannabis achieves pharmacologically.

This week we arrive at the darker side of the same story. What happens when the endocannabinoid system doesn't work properly? What does a chronically dysregulated endocannabinoid system look like from the outside — as experienced by a real person, in a real body, every day?

A 2025 review published in Current Issues in Molecular Biology by Mario García-Domínguez at the Universidad de Navarra provides one of the most comprehensive analyses to date of the endocannabinoid system's role in fibromyalgia. It connects everything we have covered in the last two weeks — the receptors, the molecules, the signalling cascades — to a clinical condition affecting hundreds of millions of people worldwide. Understanding this connection matters for anyone trying to understand what cannabis is actually doing in the human body, and why.

What Fibromyalgia Is — And Why It Has Been So Hard to Explain

Fibromyalgia is a chronic condition characterised by widespread musculoskeletal pain, persistent fatigue, sleep disturbances, and cognitive impairments — a cluster that includes difficulty with memory and concentration often called fibrofog. The pain varies in intensity and location and is linked to sensitivity at specific areas known as tender points.

Widespread Pain

Musculoskeletal pain across multiple body regions, linked to sensitivity at tender points. Varies in intensity and location, often described as burning, aching, or stabbing.

Persistent Fatigue

Chronic exhaustion that is not relieved by rest, often described as profound and disproportionate to any physical activity undertaken.

Sleep Disturbance

Non-restorative sleep, difficulty maintaining sleep, and frequent waking — creating a cycle where poor sleep worsens pain sensitivity and pain disrupts sleep.

Fibrofog

Cognitive impairments including memory loss, difficulty concentrating, and slowed mental processing — often as debilitating as the physical symptoms.

It affects 6.4% of the US population and between 2.4% and 3.3% in Europe and South America — significantly more prevalent in women. It is not rare. It is one of the most common chronic pain syndromes on the planet, affecting hundreds of millions of people globally.

What has made fibromyalgia so difficult to treat, and historically so difficult to take seriously in medical settings, is that its underlying mechanisms have resisted clear explanation. There is no obvious tissue damage visible on scans. There is no single biomarker. For decades, patients were told the pain was psychological. The condition was real and debilitating, but the biology behind it was opaque. What is now emerging from the research is a different picture. The problem may not be in the joints or muscles themselves. The problem may be in the system responsible for regulating how pain signals are processed, amplified, and dampened — and that system is the endocannabinoid system.

The Clinical Endocannabinoid Deficiency Hypothesis

The central theoretical framework the review examines is called Clinical Endocannabinoid Deficiency — CECD. The hypothesis is straightforward: in some individuals, the endocannabinoid system operates chronically below its optimal level. The system that is supposed to modulate pain, regulate sleep, stabilise mood, and dampen inflammation is not producing enough, not signalling effectively, or not maintaining adequate receptor sensitivity. The result is a body that cannot properly regulate its own experience of pain and discomfort.

This hypothesis would explain much of what makes fibromyalgia so puzzling. If the problem is systemic underfunction of the endocannabinoid system — rather than localised tissue damage — then of course there would be no obvious structural abnormality on imaging. The problem would be functional, not structural. The pain would be real, widespread, and variable because the system responsible for dampening and contextualising pain signals across the entire nervous system is impaired.

"If the problem is a systemic underfunction of the endocannabinoid system, then of course there is no structural abnormality on imaging. The problem is functional. The pain is real — the dampening system is what's failing."

The CECD hypothesis also directly connects to the synaptic signalling mechanism we described in the anandamide piece. Endocannabinoids work as retrograde messengers — released by postsynaptic neurons, travelling backwards across the synapse, and binding to presynaptic CB1 receptors to suppress the release of glutamate and other excitatory neurotransmitters. This mechanism is the brain's primary tool for preventing pain signals from being over-amplified. If that tool is impaired, pain signals propagate more freely. The threshold for what feels painful is lowered. Everything hurts more than it should.

What the Endocannabinoid System Is Actually Doing in Pain Regulation

The review provides a detailed account of the endocannabinoid system's role in pain modulation that clarifies precisely why a deficiency in this system would produce the pattern of symptoms seen in fibromyalgia.

ECS Pain Regulation — Key Mechanisms Involved in Fibromyalgia

  • Spinal Cord CB1 receptors are present in the dorsal horn — the primary relay station for pain signals entering the central nervous system. Endocannabinoid signalling here suppresses pain transmission before it reaches the brain.
  • Fascial Tissue CB1 and CB2 receptors have been identified in fascial tissue — the connective network covering and connecting muscles throughout the body. A direct mechanism by which ECS deficiency could produce the diffuse musculoskeletal pain of fibromyalgia.
  • Joint Protection CB1 activation blocks inflammatory degradation of connective tissues. When synovial cells are exposed to the inflammatory cytokine TNF-alpha, they secrete enzymes that degrade cartilage. Anandamide inhibits this process — ECS deficiency removes this protective mechanism.
  • Retrograde Brake Endocannabinoids released by postsynaptic neurons travel backwards across synapses to suppress further excitatory neurotransmitter release. This is the nervous system's volume control on pain. When this brake is compromised, pain sensitisation is amplified system-wide.

The Paradox in the Blood Data

Here is where the research becomes genuinely counterintuitive — and requires careful interpretation.

Several studies cited in the review have measured circulating endocannabinoid levels in fibromyalgia patients and found them to be elevated, not depleted. Anandamide concentrations were significantly higher in fibromyalgia patients than in healthy controls. Levels of 2-AG, OEA, PEA, and SEA — related endocannabinoid-like molecules — were also increased. At first glance this seems to contradict the deficiency hypothesis. If endocannabinoid levels are higher in fibromyalgia patients, how can the condition be caused by deficiency?

The Compensatory Mechanism

The review interprets the elevated blood levels as a probable compensatory response — the system producing more of these molecules in response to inadequate function at the receptor level. The same phenomenon is well known in other hormonal systems: when receptors become less responsive, the body increases production of the signalling molecule in an attempt to compensate. The elevated circulating levels may reflect not abundance but distress — a body working harder than it should to achieve an effect it is struggling to produce.

This interpretation is also consistent with the exercise research from last week. Long-term regular exercise was associated with decreased baseline endocannabinoid levels — the body adapting by upregulating FAAH, the enzyme that degrades anandamide, in response to repeated elevation. A body chronically producing excess endocannabinoids as a compensatory response may develop a similar pattern of accelerated degradation, creating a cycle that perpetuates the deficiency rather than correcting it.

The Menstrual Cycle Connection

One of the most striking findings in the review involves the relationship between the menstrual cycle and fibromyalgia diagnosis. It illuminates the endocannabinoid system's hormonal sensitivity in ways with real clinical implications.

Anandamide levels fluctuate across the menstrual cycle in healthy women. During the follicular phase — the first half — AEA levels are relatively high. During the luteal phase — the second half — progesterone upregulates FAAH, the anandamide-degrading enzyme, causing AEA levels to fall. A study found that this drop in anandamide during the luteal phase was associated with significantly increased sensitivity to pressure pain. And in a particularly striking finding: some participants met the diagnostic criteria for fibromyalgia during the luteal phase — the low-AEA phase — but not during the follicular phase, when AEA was higher.

This is not a peripheral observation. It suggests that the boundary between fibromyalgia and normal pain sensitivity may, for some individuals, be a matter of endocannabinoid tone — and that tone fluctuates with hormonal cycles. It may help explain the significantly higher prevalence of fibromyalgia in women. It also opens a question about whether hormonal fluctuations more broadly interact with endocannabinoid function in ways that contribute to chronic pain vulnerability across multiple conditions.

The Sleep Dimension

The review addresses the endocannabinoid system's role in sleep regulation — directly relevant to fibromyalgia because sleep disturbance is one of its most disabling features.

The pineal gland produces both melatonin and 2-AG in a circadian rhythm, partially regulated through CB2 receptor activation in the suprachiasmatic nucleus — the brain's master clock. Anandamide has also been shown to play a role in sleep onset. In a person with endocannabinoid deficiency, both the sleep regulatory function and the pain modulatory function would be impaired simultaneously.

The Cycle That Sustains the Condition

The characteristic pattern of fibromyalgia — pain that worsens with poor sleep, and sleep that is disrupted by pain — may not be two separate problems feeding each other. It may be one problem: a dysregulated endocannabinoid system failing at both pain regulation and sleep regulation at the same time, from the same underlying deficiency.

What Cannabis-Based Therapies Have Shown

The review surveys the clinical evidence for cannabis-based treatments in fibromyalgia, covering studies from 2011 to 2024. The picture is promising but not yet definitive.

Clinical Evidence — Key Study Findings

  • 2019 study: 50% reduction in pain intensity in 81% of fibromyalgia patients after six months of medical cannabis treatment
  • Israeli survey: 94% reported pain relief, 93% improved sleep, 87% reduced depressive symptoms, 62% reduced anxiety
  • 2024 study: cannabis combined with oxycodone reduced opioid consumption by 35% without affecting cannabis use frequency
  • 2024 low-dose medical cannabis study: substantial reduction in pain intensity and improvements in physical and mental state in the majority of participants
  • Nabilone (synthetic cannabinoid): significant reductions in pain, anxiety, and overall fibromyalgia impact in randomised controlled trials
  • Systematic review of 17 studies (2021): cannabis-based medicines may be effective for pain relief and sleep improvement — moderate quality evidence

The anti-inflammatory properties of CBD combined with the analgesic and muscle-relaxant properties of THC appear to produce a synergistic effect across fibromyalgia's multiple symptom domains. This is biologically coherent — the condition involves dysregulation across pain, mood, sleep, and inflammation, and a therapy that modulates the endocannabinoid system broadly would be expected to address multiple symptoms simultaneously rather than one in isolation.

The honest limitation is that most of this evidence comes from observational studies, surveys, and small trials. Randomised controlled trials with large sample sizes and long follow-up periods are largely absent. The evidence is promising and biologically well-motivated, but it is not yet at the standard required to establish definitive clinical guidelines. Patients should consult healthcare professionals before considering cannabis as a treatment, as individual responses can vary significantly.

What This Means for the Cannabis Community

The fibromyalgia research adds a critical dimension to the understanding of cannabis that this series has been building week by week.

We established that the endocannabinoid system is the body's own regulatory network — producing anandamide and 2-AG to manage pain, mood, sleep, anxiety, and inflammation. We established that exercise activates this system. This week's paper adds: when this system chronically underperforms, the result is not just a mildly worse baseline mood. The result can be a debilitating condition — widespread pain, exhaustion, cognitive impairment, and disrupted sleep — affecting millions of people who often spend years being told nothing is physically wrong with them.

Cannabis, in this context, is not a recreational novelty or a pharmaceutical shortcut. It is a plant-derived intervention targeting a specific physiological system that, in a significant proportion of the population, is not functioning adequately. The CB1 and CB2 receptors that THC and CBD interact with are the same receptors that are failing to do their job in fibromyalgia patients. The anandamide that cannabis mimics is the same molecule that fluctuates with the menstrual cycle and drops to a level that temporarily meets the diagnostic threshold for fibromyalgia.

"For many people in genuine physiological distress, cannabis may not be making them high. It may be making them feel normal — because it is restoring a function the body is struggling to maintain on its own."

This is what understanding the endocannabinoid system means in practice. Not just a more sophisticated explanation for why cannabis makes some people feel good. A clearer picture of why, for many people in genuine physiological distress, it may be making them feel normal — because it is restoring a function the body is struggling to maintain on its own.

The Endocannabinoid System Series — The Grower's Connect

Source Study: García-Domínguez M (2025) Role of the Endocannabinoid System in Fibromyalgia. Curr. Issues Mol. Biol. 47, 230. doi:10.3390/cimb47040230 — Program of Immunology and Immunotherapy, CIMA-Universidad de Navarra, Pamplona, Spain. Published March 27, 2025.
The Certified — The Grower's Connect  ·  thecertified.co.za
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Your Body Makes Its Own Cannabis — And Running Is the Key That Unlocks It

own cannabis
Your Body Makes Its Own Cannabis — And Running Is the Key That Unlocks It | The Certified
The Grower's Connect
The Series

Week 5 of The Certified's plant science series. Previously: sucrose stem infusion and 30%+ yield increases, cannabis and the brain, growing a plant from a single cell, and what's actually inside your cannabis flower. This week: the receptor you share with the plant.

Plant Science · The Endocannabinoid System

Your Body Makes Its Own Cannabis — And Running Is the Key That Unlocks It

Scientists have been searching for decades for what causes the runner's high. The endorphin theory turned out to be mostly wrong. What the evidence now points to is something far more interesting — your body producing its own versions of the compounds found in cannabis, triggered by exercise.

The Grower's Connect  ·  2025  ·  11 min read
14/17 Studies confirmed AEA rise after exercise
571 Human participants across 21 trials
70–85% Max heart rate sweet spot for release
Listen to this article Your Body Makes Its Own Cannabis — And Running Is the Key That Unlocks It

Five weeks into this series and we have moved from the plant outward. We examined what sucrose does inside the stem. We looked at how the brain responds to decades of heavy use. We watched scientists coax a naked cell back to life. We mapped the microscopic architecture of the flower itself. This week we turn to something that connects the plant to the person in a way most growers have never considered.

Your body has its own endocannabinoid system. It produces its own cannabinoid-like molecules. And a growing body of peer-reviewed evidence suggests that moderate-intensity endurance exercise — running, specifically — is one of the most reliable ways to trigger their release. This isn't fringe science or wellness marketing. It's a systematic review published in The Neuroscientist, covering 21 human clinical trials and 571 participants.

The implications run in two directions simultaneously. For the cannabis consumer, it tells you something important about what the plant is actually binding to — and why it works the way it does. For the grower, it reframes what you are cultivating. You are not producing a foreign substance that overrides the brain. You are producing plant-based versions of molecules the brain already knows, already produces, and already uses to regulate mood, pain, anxiety, and motivation.

First, the Endorphin Myth

Before we get into what the evidence actually shows, it's worth clearing the ground of what it doesn't show — because most people have been told the wrong story for decades.

The runner's high was first attributed to endorphins in the 1980s. The idea was straightforward: intense exercise releases endorphins, endorphins bind to opioid receptors, opioid receptors produce euphoria. It was widely reported, widely believed, and is still repeated today.

The problem is that endorphins are hydrophilic molecules — water-soluble. The blood-brain barrier is largely impermeable to water-soluble molecules. Peripheral endorphins physically cannot cross into the brain in meaningful quantities. The machinery needed to produce the runner's high is inside the brain. The endorphins produced in the body largely cannot reach it.

The evidence backed this up directly. When researchers blocked opioid receptors entirely using naltrexone — preventing anything from binding to those receptors — the runner's high happened anyway. Euphoria was still present. Anxiety was still reduced. The opioid system wasn't the mechanism. So what was?

"When researchers blocked the opioid system entirely, the runner's high happened anyway. Euphoria was still present. Anxiety was still reduced. The endorphin theory was wrong."

The Endocannabinoid System — Your Body's Built-In Cannabis

In the early 1990s, researchers made two discoveries that changed the picture completely. In 1992, a molecule was identified in the brain that bound to the same receptors as THC. It was named anandamide — from the Sanskrit word for bliss. In 1995, a second molecule was discovered: 2-arachidonoyl glycerol, known as 2-AG.

Both are endocannabinoids — cannabinoid-like molecules produced naturally inside the body. Both are lipophilic, meaning fat-soluble. And critically, fat-soluble molecules can cross the blood-brain barrier with ease. Unlike endorphins, endocannabinoids produced in the body can actually reach the brain.

From the plant THC & CBD

Plant-derived cannabinoids that bind to CB1 and CB2 receptors in the brain. THC produces psychoactive effects via CB1. CBD modulates the system more broadly. Both are fat-soluble and cross the blood-brain barrier.

From your body AEA & 2-AG

Endogenous cannabinoids produced by the brain itself. Anandamide binds primarily to CB1 — the same receptor as THC. 2-AG is a full agonist at both CB1 and CB2. Exercise triggers their release into circulation.

The endocannabinoid system they activate regulates synaptic transmission, mood, reward, anxiety, appetite, memory, neuroprotection, and neuroinflammation. It also plays important roles in neural development. When a cannabis grower talks about what THC does in the brain, they are talking about what the brain's own endocannabinoid system does naturally. THC is a plant-based key to a lock the body built for itself. Anandamide is the body's own key to that same lock.

What the Review Found — 21 Studies, 571 People

The systematic review published in The Neuroscientist screened 278 records and included 21 human clinical trials meeting strict criteria: aerobic exercise, minimum 20 minutes, endocannabinoid blood levels measured before and after, published in peer-reviewed journals. The 571 participants included healthy adults, athletes, people with PTSD, major depression, chronic pain, and substance use disorder.

The Headline Numbers

  • 14 of 17 studies found a significant increase in anandamide after acute exercise — an 82% replication rate
  • Only about half the studies found an increase in 2-AG, likely due to small sample sizes and greater biological variability
  • 76% of studies found increases in OEA, another endocannabinoid-like molecule, after exercise
  • All 4 long-term exercise studies found endocannabinoid levels decreased after programs of 12 weeks or more
  • Opioid blockade with naltrexone did not inhibit endocannabinoid release, euphoria, or anxiety reduction after running

For a field studying a molecule that degrades quickly and is difficult to measure, an 82% replication rate across independent research groups, different participant populations, and different countries is notable.

Intensity Is Everything — The 70 to 85% Window

One of the most practically useful findings in the review is that endocannabinoid release is not simply triggered by moving your body. It is triggered by moving your body at the right intensity.

A pivotal study tested the same participants on four separate days at four different intensities: walking at under 50% of maximum heart rate, and running at roughly 70%, 80%, and 90% of maximum heart rate. The result was clean: only the two middle intensities — approximately 70% and 80% of maximum heart rate — produced a significant increase in anandamide. Walking produced nothing. High-intensity running at 90% produced nothing.

The Sweet Spot

The review's recommendation, drawn from accumulated evidence, is 70% to 85% of age-adjusted maximum heart rate for at least 30 minutes. In practical terms this is a pace where you can speak but feel genuinely challenged — sustainable for 30 to 45 minutes, but not a stroll. Duration should be at least 20 minutes. Peak mood benefits appear around 30 to 35 minutes. Endocannabinoid levels in the blood peak immediately after exercise and can be detected for up to 15 minutes post-exercise.

What the Endocannabinoids Are Actually Doing

The runner's high has four classically described components: euphoria, reduced anxiety, reduced pain sensitivity, and sedation. Here is what the evidence shows for each in relation to endocannabinoids.

Euphoria

Strong evidence

Endocannabinoid levels were roughly twice as high after running as walking. Euphoria tracked the same pattern. Blocking opioid receptors with naltrexone did not reduce either the endocannabinoid release or the euphoria — ruling out endorphins as the mechanism.

Anxiety Reduction

Strong evidence

8 out of 10 studies found reduced anxiety after acute exercise. Higher endocannabinoid increases correlated with greater anxiety reductions. This held even in PTSD, major depression, and substance use disorder populations.

Pain Reduction

Mixed evidence

Results were inconsistent across studies. One study found significant hypoalgesia after 30 minutes of running. Another found no effect in chronic pain patients. Appears to depend heavily on intensity, timing, and participant health status.

Sedation

No evidence yet

None of the 21 studies measured or detected sedation effects after exercise. A mouse study suggests post-exercise sedation may be a non-specific fatigue response that does not require endocannabinoid signalling at all.

The Long-Term Paradox

Here is the finding that surprised the researchers most — and has the most significant implications for anyone thinking about regular exercise and the endocannabinoid system.

After acute exercise, endocannabinoids go up. But after long-term regular exercise programs lasting 12 weeks or more, all four studies that measured endocannabinoid levels found they went down. Not just back to baseline. Measurably below it.

The mechanism proposed is an upregulation of FAAH — fatty acid amide hydrolase — an enzyme that breaks down anandamide. In physically active people, FAAH activity in lymphocytes was found to be higher than in sedentary controls. The body, it appears, compensates for repeated endocannabinoid elevation by becoming more efficient at clearing it. The same homeostatic intelligence that governs tolerance to cannabis in regular users appears to operate in regular exercisers — not through receptor downregulation but through accelerated degradation of the molecule itself.

What this means practically is not yet clear. It may be neutral — the body adapting its baseline without losing the capacity for acute elevation during exercise. Or it may have implications for mood regulation in long-term athletes. The review flags this as a priority for future research.

"The same homeostatic system that governs cannabis tolerance in regular users appears to operate in regular exercisers — not through receptor changes, but through faster degradation of the molecule itself."

The Stress Connection

The review identifies a relationship between the endocannabinoid system and the stress response that goes beyond exercise-induced euphoria.

Cortisol — the primary stress hormone — and anandamide levels were found to correlate positively. When exercise drove cortisol up, anandamide went up with it. In another study, a social stress test also increased anandamide. The researchers frame this through allostasis — the body's system for maintaining stability through change. Exercise is itself a stressor. The endocannabinoid release it triggers may be part of the body's mechanism for modulating how that stress is experienced, buffering the physiological stress signal with a neurobiological one that promotes calm and positive affect.

A study of cosmonauts during spaceflight adds a striking data point. In cosmonauts experiencing low stress, endocannabinoids were elevated. In those experiencing high stress and motion sickness, endocannabinoid elevation was absent and cortisol surged. The endocannabinoid system appears to function, at least in part, as a stress buffer — one that can be depleted by excessive stress rather than activated by it.

This is directly relevant to understanding what cannabis does therapeutically. When patients report using cannabis for anxiety, stress, or mood regulation, they are not introducing a foreign chemical that overrides normal function. They are supplementing a system that exists specifically to perform those regulatory functions — one that can be overwhelmed, depleted, or dysregulated by the conditions of modern life.

What This Means for Growers and Consumers

The relevance of this research to cannabis cultivation runs deeper than it first appears.

For anyone who grows and also uses cannabis, understanding that THC and anandamide bind to the same receptor — that the plant molecule is essentially mimicking a molecule your body already produces — reframes the experience of using cannabis in a meaningful way. It is not an alien substance producing an artificial state. It is a plant-derived key fitting a lock your brain evolved for its own purposes.

For medical growers and producers, the endocannabinoid research strengthens the biological rationale for cannabis as medicine in ways that go beyond anecdote. The anxiety reduction, mood elevation, and pain modulation that cannabis produces are all functions of the endocannabinoid system — documented in drug-free exercise studies, across hundreds of participants, in peer-reviewed journals.

And for the series of conversations we have been having here on The Grower's Connect — about what the plant is at a cellular level, what its flowers are under a microscope, what happens in the brain over a lifetime of use — this piece adds something important. The plant and the person share a receptor. The endocannabinoid system is the bridge between them. And running, it turns out, is one of the oldest ways the body has of activating that bridge on its own.

The Grower's Connect — Plant Science Series

Source Study: Siebers M, Biedermann SV, and Fuss J (2022) Do Endocannabinoids Cause the Runner's High? Evidence and Open Questions. The Neuroscientist. 2023;29(3):352–369. doi:10.1177/10738584211069981 — Institute of Forensic Psychiatry and Sex Research, University of Duisburg-Essen, Germany. Published 2022.
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What’s Actually Inside Your Cannabis Flower

cannabis flower
What's Actually Inside Your Cannabis Flower — And Why Understanding It Could Change How You Grow | The Certified
The Grower's Connect
The Series

Week 4 of The Certified's plant science series. Previously: sucrose stem infusion and 30%+ yield increases, cannabis and the brain, and growing a plant from a single naked cell. This week: what the flower actually is.

Plant Science · Florogenesis & Flower Architecture

What's Actually Inside Your Cannabis Flower — And Why Understanding It Could Change How You Grow

Israeli researchers put cannabis flowers under a scanning electron microscope and mapped exactly how they form, branch, and develop. What they found challenges some of the most widely held assumptions in cultivation — including whether your plant is ever truly vegetative.

The Grower's Connect  ·  2025  ·  10 min read
7 Orders of branching in one inflorescence
2 Flowers at every single node
Day-neutral Flower initiation is not photoperiod-triggered
Listen to this article What's Actually Inside Your Cannabis Flower

Four weeks into this series and the direction has been consistent. We looked at sucrose pushing through a stem to drive yield. We looked at brain scans showing what decades of heavy use does to working memory. We looked at scientists stripping cells naked to unlock the genetics of the future. This week we slow down and look at something that every grower interacts with every single day — the flower itself.

Not the bud as a product. The flower as a biological structure. What it actually is. How it actually forms. And why understanding that might quietly change how you think about your grow.

A 2019 study published in Frontiers in Plant Science by researchers at the Volcani Centre in Israel used scanning electron microscopy and stereomicroscope imaging to map cannabis flower development in detail across three cultivars. What they found is genuinely illuminating — and in some cases, directly challenges assumptions that are deeply embedded in everyday cultivation practice.

Your Plant Is Never Truly Vegetative

Let's start with the finding that will bother some growers most: the idea of a clean vegetative phase — where your plant is just building structure and hasn't started thinking about flowers — is probably not accurate.

The researchers found that under long photoperiod conditions, the ones growers call vegetative, cannabis plants were already producing solitary flowers in the axils of every leaf node. Not just flower primordia visible only under a microscope. Actual flowers. Two of them, sitting in the base of every leaf petiole, one on each side, each subtended by a bract.

In two of the three cultivars studied, these solitary flowers reached full anthesis — complete maturity — under 18/6 light. The plant had not been flipped. It had not been told to flower. It flowered anyway.

What this means scientifically is that cannabis flower initiation appears to be age-dependent and driven by internal signals, not triggered by photoperiod. The plant doesn't wait for the light to change. It begins its reproductive programme on its own schedule, governed by developmental age and internal hormonal cues, not the timer on your ballast.

"When you flip to 12/12, you are not telling the plant to start flowering. You are telling it to dramatically change the architecture of its branching system — around a process it has already begun."

The implication is worth sitting with. When you flip to 12/12, you are not telling the plant to start flowering. You are telling it to dramatically change the architecture of its branching system — to compress and intensify the inflorescence structure it has already begun building. That is a fundamentally different mental model of what the flip does.

The Phytomer — The Repeating Unit You're Working With

To understand what the researchers found, you need one concept: the phytomer. It is the basic repeating building block of the cannabis plant, and every node on your plant is one.

Each phytomer consists of four elements — an internode (the section of stem between nodes), a large fan leaf, two bracts, and two solitary flowers sitting in the base of the leaf petiole. This structure repeats up the entire plant, from the lowest node to the highest. The same unit. Over and over. And critically, the same structure is present whether the plant is under long or short photoperiod.

The Four Elements of Every Phytomer

  • The internode — section of stem between nodes, elongated under long photoperiod, compressed under short
  • The fan leaf — large photosynthetic compound leaf, reducing in size and lobe number as flowering progresses
  • Two bracts — modified leaf structures at the leaf petiole base, subtending the flowers on each side
  • Two solitary flowers — one in the axil of each bract, present at every node under both long and short photoperiod

What changes when you flip to 12/12 is not the phytomer itself. What changes is the scale and compression of the phytomers. Under long photoperiod they are large and spread out, with full-sized fan leaves and extended internodes. Under short photoperiod they miniaturise and compress, leaves reduce dramatically, internodes shorten, and the entire structure densifies into what we recognise as an inflorescence.

When you look at a cola, you are not looking at one thing. You are looking at a compressed stack of phytomers, each containing two individual flowers, each developing on its own timeline, surrounded by its own bract, with its own trichome development happening at its own rate.

What a Cannabis Flower Actually Is

Here is where the microscope work gets interesting for anyone who has ever looked closely at a developing bud and wondered what exactly they were looking at.

Each individual female flower is a remarkably minimal structure. Under the scanning electron microscope, the researchers mapped its development in sequential stages. The flower consists of a carpel — the ovule-bearing structure — enclosed within a perigonal bract: a specialised leaf-like structure that wraps around and envelops the ovary. This perigonal bract is different from the larger subtending bract that sits at the leaf base. It is a second, inner bract that directly surrounds the flower itself.

During early flower development a perianth — an early-stage outer floral envelope — is also present. The researchers documented that it degenerates as the flower matures, losing its structure and becoming barely visible as a thin membrane. By the time the flower approaches maturity, what you are looking at is essentially just the carpel, wrapped in the perigonal bract, with two stigmas extending from the top.

The Detail That Matters Most

Glandular trichomes begin developing on the perigonal bract before the stigmas have fully elongated. The structures producing every cannabinoid and terpene you are cultivating for form and begin their production cycle early in flower development — while the flower is still forming around them. Trichomes are not a late-stage feature.

Those two stigmas — the paired white hairs that growers use as their primary visual indicator of flower development — elongate unevenly, extending from the perigonal bract as the flower matures. Papilla cells develop on the stigma surface, covering it from tip to base. But by this point, trichome development is already underway.

The Inflorescence — Why Dense Branching Is the Point

Under short photoperiod, cannabis develops what the researchers formally classify as a highly branched compound raceme. Understanding this classification explains the structural logic behind what you are trying to achieve with training, pruning, and canopy management.

A raceme is an inflorescence where the main axis continues to grow and produce lateral flowering structures along its length, rather than terminating. Compound means those lateral structures themselves branch and produce further inflorescences of higher order. In cannabis, the researchers documented up to seven visible orders of branching within a single inflorescence — seven levels of nested branchlets, each carrying its own phytomers, each carrying its own pairs of flowers.

The density of your inflorescence — the compactness of your bud — is directly related to how many of these branching orders develop and how much they compress. The more branching orders that develop, the more flowers per unit of stem length, the more bracts per unit of volume, and therefore the more trichome-bearing surface area per gram of inflorescence.

This is the structural basis for trichome density in high-quality cannabis. It is not simply genetics, though genetics sets the ceiling. It is the plant's branching programme executing under the right conditions, compressing as many bract surfaces as possible into as small a space as possible.

Three Cultivars, Three Completely Different Endings

One of the most illuminating findings in the study is what happened at the very tip of the inflorescence in each of the three cultivars — because each one behaved completely differently at the same anatomical location.

Cultivar NB140

High THC · Indica dominant

The apical meristem eventually terminated by differentiating a normal, fully formed female terminal flower — about 8 to 10 days after the first stigmas appeared. The standard expected endpoint.

Cultivar NB150

High THC · Sativa-Indica mixed

The apical meristem terminated by producing a hermaphrodite terminal flower — with both pistils and anthers present simultaneously. Visible under microscope. Likely triggered by stress or ethylene and gibberellin fluctuations.

Cultivar NB130

~7% THC / 7% CBD · Sativa dominant

The inflorescence meristem simply never terminated. Seven months after the flip to short photoperiod, it was still producing new phytomers. An open, indeterminate structure with no programmed endpoint.

All three of these endpoints are governed by genetic programming in the meristem — by the molecular identity of that growing tip and its sensitivity to the hormonal signals that eventually tell it to stop. Different genetics, different outcomes at the same location in the plant. The same photoperiod, the same environment, three completely different developmental conclusions.

The Questions This Should Make You Ask

The value of this kind of research for growers is not in the technical detail itself. It is in the questions it generates. Here are the ones worth sitting with.

Questions from the Research

  1. If your plant is already producing flowers under vegetative conditions, what does extending your vegetative period beyond a certain developmental age actually accomplish? At what point are you simply accumulating more phytomers rather than building a fundamentally different plant?
  2. If trichome development begins before stigma elongation is complete, what does that mean for your interpretation of maturity indicators? Is the pistil colour change you use as a harvest signal actually lagging behind trichome development in a predictable way?
  3. If the density of your inflorescence is determined by how many branching orders develop, what does your environmental management during the first two weeks of flower do to that branching programme? The stretch is not just about height — it is about the architectural decisions the plant is making.
  4. If different cultivars terminate their apical meristems through completely different mechanisms, is the concept of a universal harvest window based on weeks of flower actually meaningful across different genetics? Or is each cultivar following its own internal clock to a structurally different endpoint?
  5. If the phytomer is the same repeating unit at every node, what does defoliation at different stages actually remove in terms of that repeating architecture — and what is the downstream effect on the phytomers above?

These are not rhetorical questions. They are the kinds of questions that, once asked, tend to change how you observe your plants day to day. You start looking for the answers in the plant, not just in a feeding chart.

What This Connects to in Our Previous Work

There is a thread running through this entire series worth naming directly.

In week one, we saw that the cannabis plant's response to sucrose infusion was extraordinarily precise — 0.5 bar worked, 2 bar damaged. The mechanism was at the cellular and molecular level, but the outcome was visible in flower mass and cannabinoid yield. In week two, we saw that what cannabis does to the brain is specific to particular regions — not a general effect, but a targeted one in areas with high CB1 receptor density. In week three, we saw that protoplast viability at isolation determined everything downstream. The starting conditions set the ceiling.

"The plant is not a vague system responding to vague inputs. It is a precise biological machine executing a specific developmental programme, responding to specific signals, at specific times, in specific structures."

The common thread is precision. The more clearly you can see the plant's developmental programme — the architecture of the phytomer, the timing of trichome development relative to flower development, the branching programme that builds your inflorescence — the more accurately you can work with it rather than against it.

That is the argument for growers engaging with this kind of science. Not because you need to run scanning electron microscopes in your facility. But because the mental model you carry of what is happening inside your plant shapes every decision you make about light, environment, timing, and intervention. The more accurate that model, the better those decisions tend to be.

The Grower's Connect — Plant Science Series

Source Study: Spitzer-Rimon B, Duchin S, Bernstein N and Kamenetsky R (2019) Architecture and Florogenesis in Female Cannabis sativa Plants. Front. Plant Sci. 10:350. doi: 10.3389/fpls.2019.00350 — Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel. Published April 2, 2019.
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Scientists Just Grew Cannabis From a Single Cell — And It Changes Everything

cannabis from a single cell
Scientists Just Grew Cannabis From a Single Cell — And It Changes Everything About the Future of This Plant | The Certified
The Grower's Connect
The Series

Week 3 of The Certified's plant science series. Previously: sucrose stem infusion and 30%+ yield increases, and what brain scans reveal about cannabis and working memory. This week: the future of cannabis genetics starts at the cellular level.

Plant Science · Cannabis Biotechnology

Scientists Just Grew Cannabis From a Single Cell — And It Changes Everything About the Future of This Plant

Czech researchers have achieved only the second-ever successful cultivation of cannabis protoplasts — naked plant cells stripped of their walls — and coaxed them into dividing. Here's why that quiet laboratory milestone could reshape how cannabis is bred, cloned, and engineered at a genetic level.

The Grower's Connect  ·  June 2025  ·  10 min read
2nd Ever achieved globally
83.2% Peak cell viability
9 Cannabis cultivars tested
Listen to this article Scientists Just Grew Cannabis From a Single Cell

Three weeks on The Grower's Connect, and a clear theme has emerged. We started by looking at how feeding sucrose directly into the stem at precisely the right pressure could push yields up by over 30%. Then we examined what heavy cannabis use does to the brain, and found the science far more nuanced than headlines suggest. This week, we go deeper still, into the cellular machinery of the plant itself. Because a quietly remarkable study just published in Frontiers in Plant Science has brought us one step closer to something that could fundamentally change cannabis cultivation as we know it.

The word "protoplast" won't mean much to most growers. By the end of this piece, it will, and you'll understand why it matters.

What Is a Protoplast, and Why Does It Matter?

A protoplast is simply a plant cell with its cell wall enzymatically removed. What's left is the naked cell, just the plasma membrane and everything inside it. That sounds destructive, but it's actually the opposite. Strip away the cell wall and something remarkable happens: the cell loses its identity. It forgets, in a sense, what it was programmed to be. It becomes capable of becoming anything.

Under the right conditions, a single protoplast can divide, redifferentiate, and regenerate into a complete, genetically identical plant. This process, called somatic embryogenesis or protoplast-to-plant regeneration, is the foundation of some of the most powerful tools in modern plant biotechnology, including genetic transformation and CRISPR-based genome editing.

The reason this matters for cannabis specifically is that the plant has been notoriously difficult to work with at the cellular level. Unlike tobacco, tomato, or Arabidopsis, the laboratory workhorse of plant biology, cannabis has resisted almost every attempt to regenerate a whole plant from isolated cells. That resistance has been a major bottleneck for cannabis research and breeding for decades.

"Strip away the cell wall and the cell loses its identity. It forgets what it was programmed to be — and becomes capable of becoming anything. That is the entire point."

What the Study Actually Did

Researchers at Palacký University Olomouc in the Czech Republic, led by Daniel Král, set out to crack that bottleneck. Published in June 2025 in Frontiers in Plant Science, the study reports only the second successful establishment and partial regeneration of cannabis protoplast cultures ever documented in scientific literature.

The team worked with nine cannabis cultivars, all industrial hemp varieties with varying CBD content, including USO 31, Finola, Fédora 17, Futura 75, and others. The work involved two distinct phases: first, optimising the conditions for protoplast isolation, and second, attempting to get those isolated cells to survive, divide, and form early-stage cell clusters called microcalli.

Getting the donor material right was everything. The researchers tested protoplast isolation from plants at multiple developmental stages, from one-week-old seedlings all the way through to six-month-old in vitro cultures and greenhouse-grown plants. The results were unambiguous: only leaves from one to two-week-old seedlings grown in sterile in vitro conditions produced protoplasts at a useful yield and viability. Older material consistently failed. Greenhouse-grown plants failed entirely.

Study Design at a Glance

  • 9 industrial hemp cultivars tested, including both high and low CBD strains
  • Donor material tested from 1-week-old seedlings through to 6-month-old in vitro cultures and greenhouse plants
  • 5 enzyme formulations evaluated for cell wall digestion
  • Gene expression tracked at 0, 24, 48 and 72 hours post-isolation across 6 target genes
  • Extended 14-day cultivation experiment confirmed microcallus formation and cell viability
  • Palacký University Olomouc, Czech Republic — published June 2025, Frontiers in Plant Science

The best results came from the USO 31 cultivar, producing yields of up to 9.9 million cells per gram of leaf tissue, with a peak viability of 83.2%, meaning more than four in five isolated cells were alive and functional immediately after extraction.

Key Finding

Just as we saw with sucrose stem infusion — where the difference between 0.5 bar and 2 bar of pressure determined whether yields increased by 34% or fell below the control — the protoplast work shows that precise conditions at the starting point determine everything that follows. You cannot compensate downstream for poor decisions upstream.

The Isolation Process — How You Strip a Cell Wall

The enzymatic solution used to digest away the cell wall is one of the most critical variables in the entire process. The team tested five different enzyme formulations, ultimately finding that a solution containing cellulase and macerozyme in a mannitol buffer — originally developed by Matchett-Oates et al. in 2021 — performed best.

The digestion ran for 16 hours in complete darkness at 25°C without shaking. Shorter digestion periods consistently failed. Adding a washing solution both before and after filtration was critical; skipping this step caused the protoplasts to clump and aggregate, making separation impossible. Centrifugation at 1000 rpm for 10 minutes, using a sucrose density gradient, provided the cleanest separation of viable cells from cellular debris.

One important finding: adding pectolyase, an enzyme used successfully in other species and suggested by several previous cannabis studies, actually made things worse at higher concentrations, likely by causing excessive enzymatic activity that damaged the cells before they could be collected.

Getting Them to Divide — The Hard Part

Isolating protoplasts is one thing. Getting them to survive in a culture and divide is another challenge entirely. The vast majority of cannabis protoplast research has stopped at isolation. Getting cells to actually re-enter the cell cycle, to start dividing, is where the field has repeatedly hit a wall.

This study used a regeneration medium originally developed for Arabidopsis thaliana, modified slightly for cannabis, supplemented with two plant growth hormones: indole-3-acetic acid (a natural auxin) and benzylaminopurine (a cytokinin). These two hormones together are what push a dedifferentiated cell back toward division and development.

The results: cultures remained viable after three days of incubation, microscopy confirmed cells had undergone at least one division, and an extended 14-day cultivation experiment produced visible microcalli, small clusters of dividing cells, that retained viability under FDA staining. This is the proof-of-concept moment. The cells didn't just survive. They started rebuilding.

What the Gene Expression Data Revealed

This is where the study goes beyond what any grower would attempt in their facility, but it's also where the most interesting science lives.

The researchers tracked gene expression in the cultured protoplasts at 0, 24, 48, and 72 hours using RT-qPCR, a technique that quantifies how actively specific genes are being transcribed. They monitored six genes across three categories: cell proliferation, abiotic stress, and oxidative stress.

Cell Proliferation Markers

PCNA, a protein directly involved in DNA replication and used as a standard marker of cell division, was undetectable in normal leaf tissue but increased significantly after protoplast isolation, peaking at 72 hours with a threefold increase in high-viability cultures. The auxin-responsive gene IAA-2 also showed a significant increase during cultivation, peaking at 48 hours with a 3.5-fold increase, indicating that the cells were actively responding to the growth hormones in the medium.

Abiotic Stress Markers

Two genes associated with the plant stress hormone abscisic acid, PP2C-1 and LEA34, both dropped significantly after isolation and stayed low throughout cultivation. This is good news: it means the cells were not experiencing escalating abiotic stress during the culture period. They adapted to their new environment quickly rather than deteriorating under it.

Oxidative Stress — The Critical Battle

When cell walls are enzymatically digested, reactive oxygen species, essentially cellular rust, accumulate rapidly. If not neutralised, these damage the plasma membrane and kill the cell. Two antioxidant genes, APX and CAT, showed complementary activation patterns throughout cultivation, indicating the cells' own antioxidant systems were engaged and functioning. In high-viability cultures, APX expression increased 3.5-fold within 24 hours. This coordinated antioxidant response, the researchers argue, was a critical factor in enabling the cells to survive and eventually divide.

"The cells didn't just survive the isolation process. They mounted an antioxidant defence, responded to growth hormones, and started dividing. That coordinated response is the entire story."

Why Viability at Isolation Predicts Everything That Follows

One of the most practically useful findings in the study is the relationship between viability at the point of isolation and everything that happens afterwards.

High-viability cultures, those above 60% viability at isolation, showed roughly twice the PCNA expression of low-viability cultures, stronger antioxidant responses, and more robust cell division overall. Low-viability cultures, below 15%, showed reduced expression across all proliferation and stress markers, consistent with impaired capacity to divide and survive.

The implication is clear: the quality of your starting material and your isolation technique determine your ceiling. You cannot compensate downstream for poor isolation conditions upstream. In the context of cannabis biotechnology, this means the painstaking work of optimising donor plant age, cultivation conditions, enzymatic solutions, and washing protocols is not procedural box-ticking; it is the entire game.

Why This Matters for Growers — Now and in the Future

Most growers will never set foot in a protoplast laboratory. So why should any of this matter to someone running a cultivation facility, a breeding programme, or a craft grow? Because this is how the next generation of cannabis genetics gets made.

The ability to work with cannabis at the single-cell level unlocks capabilities that are simply not possible through conventional breeding. Consider what becomes possible once protoplast-to-plant regeneration is fully achieved in cannabis:

Precision Genetic Transformation

Rather than working with whole plants and hoping a genetic modification takes hold uniformly, you can transform a single cell and regenerate an entire plant from it, guaranteeing that every cell carries the intended modification. This is non-chimeric transformation — the gold standard in plant genetic engineering.

CRISPR Genome Editing

Several research groups have already demonstrated transient CRISPR delivery into cannabis protoplasts, with transformation efficiencies reaching 75% in some studies. Once stable whole-plant regeneration is achieved, targeted editing of cannabinoid pathway genes becomes a realistic breeding tool.

Somatic Hybridisation

Protoplasts from two different plant species or varieties can be fused together, creating hybrid cells that combine the genetics of both parent plants. In cannabis, where specific terpene and cannabinoid profiles are of enormous commercial value, the implications are significant.

Ploidy Manipulation

Working at the cellular level allows controlled changes to chromosome number — a technique used in other crops to create larger, more vigorous varieties. In cannabis, this pathway to polyploid breeding has barely been explored.

You should know how I feel about all this. I am simply reporting what the study found. If this is overall good for us, I will let you decide for yourself. Just be mindful that we as people can always decide the direction of our own spaces, but not the overall market's direction. Similarly with food.

The Honest Limitations

Complete plant regeneration from cannabis protoplasts has not yet been achieved. The study reports microcallus formation — early-stage cell clusters — but not organised shoot or root development from those clusters. That next step remains the critical bottleneck, and the researchers are explicit that it is unresolved.

The work was done on industrial hemp varieties, all with low THC content. Whether high-THC varieties will respond similarly to the same isolation and culture conditions is unknown. Genotype variability is a significant factor throughout the study — results that worked well for USO 31 did not always transfer to Finola or other cultivars.

Where This Is All Going

Plant biotechnology in cannabis is accelerating. The first stable genetically modified cannabis plant was created just a few years ago using Agrobacterium-mediated transformation. CRISPR constructs validated in protoplasts are already being used to edit cannabis genes. And now, the second-ever report of cannabis protoplast cultivation and division has been published, with gene expression data that confirms the cells are genuinely viable, actively dividing, and mounting appropriate stress responses.

Each of these steps is incremental. None of them is the finish line. But they are building toward a moment when cannabis breeders will have access to the same precision genetic tools that have been available for maize, tomato, and rice for decades. When that moment arrives, everything as we know it will change.

The Grower's Connect — Plant Science Series

Source Study: Král D, Šenkyřík JB and Ondřej V (2025) Early protoplast culture and partial regeneration in Cannabis sativa: gene expression dynamics of proliferation and stress response. Front. Plant Sci. 16:1609413. doi: 10.3389/fpls.2025.1609413 — Department of Botany, Faculty of Science, Palacký University Olomouc, Czechia. Published June 6, 2025.
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