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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 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.


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.
The Certified — The Grower's Connect  ·  thecertified.co.za
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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 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.
The Certified — The Grower's Connect  ·  thecertified.co.za