As a grower, you've probably heard every pitch for squeezing more out of your plants — from specialist bloom boosters to light spectrum tweaks to microbial inoculants. Most of them promise a lot and deliver a little. So when a peer-reviewed study lands showing yield improvements of 31% in flower dry mass and 34% in cannabinoid output, it's worth sitting with it for a minute.

The technique is called Plant Stem Infusion of Sucrose — PSIS for short. It's been studied in maize, barley, soybean and sweet potato for decades, but this is the first time researchers have applied it directly to cannabis. The results, published in Industrial Crops & Products (2025), are genuinely interesting — not because PSIS is going to replace your current nutrient program, but because it opens up a real conversation about how we deliver energy to flowering plants.

Let's break it all down.

What Is Plant Stem Infusion, and Where Did It Come From?

The concept is simple: rather than feeding your plant through its roots or leaves, you inject a solution directly into the stem — bypassing surface uptake entirely and delivering nutrients straight into the plant's vascular system. Think of it like an IV drip for your plant.

The method has its roots in tree care. Arborists have been injecting fungicides, insecticides and minerals into trees for decades to treat everything from Dutch elm disease to emerald ash borer infestations. The logic is solid — if the roots or bark are compromised, go around them. The same principle has since been applied to crops, with boron and calcium injections in soybeans shown to improve pod development and overall yield as far back as 1987.

Sucrose specifically became the focus of PSIS research because of what sugar does for a plant beyond just being fuel. It acts as a signalling molecule, influencing gene expression, secondary metabolism, and cellular differentiation. When you introduce exogenous sucrose at the right moment and concentration, you're not just giving the plant more energy — you're potentially pushing it toward more productive metabolic pathways.

How the Study Was Set Up

The research team at the University of Ljubljana grew 72 plants of a single CBD-dominant variety — Charlotte's Angel® (chemotype III: high CBD, low THC) — in a controlled indoor environment. Two variables were tested: the concentration of the sucrose solution (0%, 7.5%, 15%, and 30%) and the pressure at which it was delivered (0.5 bar, 1 bar, and 2 bar).

Starting on day 70 of the grow (two days into flowering), a standard 20-gauge hypodermic needle was inserted diagonally into the lowest node of each test plant, connected via IV tubing to a pressurised PVC tube filled with the sucrose solution. The system stayed live for the remainder of the grow — right through to harvest on day 133. Nine plants served as a negative control group with no infusion at all.

Measurements taken included plant height, stem and organ dry mass, chlorophyll content, net carbon assimilation, stomatal conductance, respiration, and cannabinoid yield via HPLC analysis of the top inflorescence of each plant.

What the Numbers Actually Showed

The Pressure Variable Was Everything

Here's the single most important takeaway: pressure matters more than concentration. Plants infused at 0.5 bar were the clear winners across almost every metric. They grew taller, produced significantly more flower dry mass, heavier stems, and delivered the highest cannabinoid yields. Everything above that — 1 bar and 2 bar — started working against the plant.

At 2 bar, cannabinoid yield actually dropped below the control group at certain sucrose concentrations. The plants were being overwhelmed. Think about it from a physiological standpoint: too much pressure forces too much solution into the vascular system too quickly. Instead of a gentle boost, you're creating mechanical and osmotic stress. The plant has to work to deal with it rather than benefit from it.

Flower Mass and Cannabinoid Yield

At 0.5 bar combined with 15% or 30% sucrose concentration, flower dry mass increased by up to 31% and total cannabinoid yield per plant jumped by up to 34% compared to the control group — both statistically significant results. These aren't marginal improvements. On a commercial scale, a 34% increase in cannabinoid yield per plant, without any change to genetics, lighting, or nutrient program, is a considerable number.

The dominant cannabinoid in the study was CBDA, which ranged from 10.72% to 12.42% across all groups, with no statistically significant difference between treatments in terms of cannabinoid profile — meaning the ratio of compounds didn't shift, just the total output. The plant was producing more of the same thing, not a different thing.

What About Leaf Mass?

Interestingly, all treated groups showed a reduction in leaf biomass compared to the control — though the difference wasn't statistically significant. This tracks with findings from other PSIS research: when you introduce exogenous sucrose, the plant reduces its reliance on photosynthesis. The leaves are doing less of the heavy lifting. This could partly explain why flower and stem mass went up while leaf mass edged down — the plant was redirecting energy rather than generating more of it.

Physiology: Mostly Business as Usual

One of the more reassuring findings is what didn't change. Net carbon assimilation, stomatal conductance, chlorophyll content, and photosynthetic efficiency all showed no statistically significant differences between treated and control plants. The infusion wasn't breaking anything in the plant's normal operating system.

The one exception: plants infused at 1 bar showed a significant increase in respiration on the first measurement day. More sucrose being pushed in means more metabolic activity — the plant was burning more energy to process the extra input. This wasn't observed at 0.5 bar, which again points to that gentler pressure being the sweet spot.

Why Sucrose? The Plant Science Behind the Method

Sucrose is the primary sugar that plants move around internally. When your leaves photosynthesise, they produce sucrose and ship it through the phloem to wherever the plant needs energy most — growing shoot tips, developing fruits, building roots. During flowering, the demand from inflorescences is enormous.

By supplying sucrose exogenously via the stem, the researchers were essentially supplementing that internal supply chain at a critical moment. But sucrose does more than carry energy. It's been shown to trigger the accumulation of secondary metabolites — flavonoids, phenolic acids, anthocyanins — in various plant species. In cannabis, the same logic applies to cannabinoids, which are secondary metabolites produced under specific stress and signalling conditions. More sucrose, delivered at the right time, appears to nudge the plant toward ramping up cannabinoid biosynthesis alongside the increased biomass production.

The researchers note that sucrose also influences the activity of SnRK1 — a protein kinase involved in carbohydrate metabolism and starch production. Higher sucrose availability can upregulate the pathways responsible for biomass accumulation and overall yield.

The Honest Limitations — What This Study Doesn't Tell Us

This is a pilot study. The researchers are upfront about that. It used a single variety, a single genotype, in a single controlled environment. Before PSIS becomes something any commercial grower should seriously consider rolling out, a few questions need answers:

Does it work across chemotypes? Charlotte's Angel is a chemotype III — high CBD, low THC. High-THC varieties may respond differently. The research team specifically flags this as a priority for future work.

What's the optimal sucrose concentration? The study found that concentration alone didn't produce statistically significant differences across the groups — the benefit came from the combination of low pressure and higher concentration. There's likely a more refined sweet spot that further research could identify.

How does it scale? 72 plants in a 12m² controlled chamber is a tightly managed experiment. Adapting the injection system for a large commercial canopy — with consistent needle placement, sealed injection sites, and sterile media — is a real engineering and labour challenge. The researchers acknowledge this openly.

Contamination risk. A sucrose-rich environment inside plant tissue is a potential invitation for fungal pathogens. Sterile needles and sterilised solution would be non-negotiable in any practical application.

What This Could Mean for Growers Going Forward

Let's be real — most home growers and small-scale craft operators aren't about to start injecting their plants with IV drips this season. But that's not the point. The value of research like this is in what it tells us about how cannabis plants work, and what possibilities exist on the horizon for cultivation technology.

For commercial operations with high-value crops, even the research question here is worth watching. Cannabis is, as the study points out, one of the most valuable crops per gram of inflorescence biomass on the planet. A 30%+ yield improvement, if it translates reliably across varieties and environments, changes the economics of a grow room in a serious way. The additional cost of the infusion system, sterile supplies, and labour could absolutely be justified at commercial scale if the yield data holds up.

For the rest of us, the broader principle is useful: the timing and mechanism of nutrient delivery matters. The plant doesn't just care what you're giving it — it cares how, when, and at what rate it arrives. This study is another reminder that innovation in cannabis cultivation doesn't always come from a new bottle on the shelf. Sometimes it comes from asking fundamentally different questions about how plants work.

The Bottom Line

PSIS isn't ready for your grow room yet. But this research lays a genuinely solid foundation. The methodology is rigorous, the results are statistically significant where they count, and the researchers are appropriately careful about what the data does and doesn't say.

The key findings are clear: low pressure (0.5 bar) with a high sucrose concentration (15–30%) delivers meaningful improvements in flower dry mass and cannabinoid yield. High pressure works against the plant. The photosynthetic system remains largely intact. And the mechanism — sucrose as both energy source and signalling molecule — is well-supported by plant science literature across multiple species.

As the legal cannabis market matures and competition increases, growers who stay close to the science are the ones who will find the edges that matter. This is one worth keeping an eye on.