Cannabis Sex Reversal Alters Trichomes and THCA Levels

Why do female cannabis flowers usually accumulate more cannabinoids than male flowers? Genetics provides part of the answer, but the structures a plant builds also matter. A plant needs specialized tissues capable of producing and storing its chemical compounds. Understanding how those tissues develop could help breeders make more informed decisions about seed production and crop consistency.

A new study in Industrial Crops and Products examines that connection by changing how cannabis plants respond to ethylene, a plant hormone involved in development.¹ Researchers induced male-like flowers on female plants and female-like flowers on male plants, then tracked changes in floral anatomy, resin glands, gene activity, and cannabinoid concentrations.

The findings suggest that cannabinoid accumulation is closely connected to the identity and composition of floral tissues. They also reveal an important distinction: changing a flower’s appearance, changing its chemistry, and improving the productivity of an entire plant are separate achievements.

Why Cannabis Flowers Need Specialized Resin Glands

Cannabis produces much of its floral cannabinoid content in glandular trichomes, the tiny resin-bearing structures responsible for a flower’s frosty appearance. These glands occur on flower-associated tissues, including bracts and sugar leaves. Female flowers generally carry more abundant glandular trichomes than male flowers.

A useful comparison is a manufacturing site. Cannabinoid-producing enzymes are part of the equipment, while glandular tissues provide the specialized production and storage space. Possessing instructions for making the equipment does not guarantee that a plant will build the same amount of production space in every organ.

This helps explain why trichomes deserve attention beyond appearance. However, counting visible glands cannot establish potency by itself. MyCannabis’s recently updated guide to assessing trichomes and flower maturity explains why visual observations work best alongside consistent sampling and chemical testing.

The new study asks what happens when researchers alter the developmental program that determines which floral structures form.

How Researchers Changed Cannabis Flower Development

The team studied a Korean cannabis landrace, meaning plant material associated with a regional cultivation history. Although traditionally associated with fiber production, this material was THC-dominant rather than CBD-dominant. Its relatively simple branching structure made developing flowers easier to examine.

Researchers used silver thiosulfate, commonly abbreviated STS, to induce male-like flowers on female plants. STS interferes with ethylene responses and already has an established role in feminized seed production. In that breeding process, genetically female plants produce pollen-bearing flowers that can supply pollen for crosses with other female plants.

For a complementary experiment, the team applied ethephon, an ethylene-releasing compound, to male plants. This encouraged the development of female-like flowers.

The scientists examined floral surfaces with scanning electron microscopy, inspected internal anatomy, measured selected gene transcripts, and analyzed cannabinoid concentrations using high-performance liquid chromatography. The molecular and biochemical analyses used three independent biological replicates, with some samples pooling tissues from multiple plants.

This combination allowed them to compare what flowers looked like, which genes were active, and which cannabinoids accumulated.

What Changed in Trichomes and Cannabinoid Levels

STS-treated female plants developed male-like floral organs while retaining a broadly female-like inflorescence arrangement. Their converted flowers had substantially fewer glandular trichomes on the calyx surfaces examined than untreated female flowers.

Those changes coincided with lower transcript abundance for THCAS and CBDAS, genes associated with the enzymes that produce THCA and CBDA. THCA is the acidic precursor that can convert to THC through heating.

Untreated female flowers contained 18.6 milligrams of THCA per gram of dried tissue. The paper describes an approximately 10% reduction in THCA content following STS treatment. The cannabinoid difference was therefore relatively modest compared with the conspicuous changes in floral structures.

The reverse treatment produced a complementary pattern. Ethephon-treated male plants developed both male and female-like flowers, with female-like flowers accounting for approximately 60% of the total. These female-like flowers had higher glandular trichome density and greater cannabinoid accumulation than untreated male flowers.

Flower Identity Adds Context to Cannabis Genetics

One useful insight is that chromosomal sex and chemical output should not be treated as interchangeable descriptions. A plant’s chromosomes help shape development, but the organs it actually forms also influence where cannabinoids accumulate.

That interpretation fits the leaf results. Male and female leaves had similar total cannabinoid concentrations under the tested conditions, even though their flowers differed substantially. The strongest differences appeared in the specialized reproductive tissues.

Related 2026 research on ethylene-driven floral plasticity examined three cannabis genotypes and found distinct responses in XX and XY plants. That work reinforces the importance of developmental timing and genetic background when investigating flower conversion.

Meanwhile, a September study of gibberellin-related gene activity during cannabis sex reversal found changes associated with floral phenotype. It did not establish a causal role for that hormone pathway. Together, these studies suggest researchers are examining an interacting developmental network rather than a single universal switch.

Why Gene Activity Does Not Tell the Whole Story

The new findings also offer a lesson in interpreting plant research. Lower THCAS transcript abundance across a flower sample does not necessarily mean that every cannabinoid-producing cell has reduced its activity.

The sample may simply contain fewer of those specialized cells. Returning to the manufacturing comparison, lower output could reflect fewer production rooms, slower equipment within each room, or both.

Because the researchers measured transcripts in bulk inflorescence tissue, they could not separate direct changes within individual cells from changes in the proportions of different tissues. They also could not exclude contributions from treatment-associated stress or effects unrelated specifically to ethylene receptors.

These limits leave a productive question for future research: does floral conversion mainly change the number of cannabinoid-producing cells, their individual performance, or some combination?

What Cannabis Breeders Can Take From the Findings

For breeders, the immediate value is a clearer framework for evaluating plants used in seed production. A treatment can successfully induce pollen-bearing flowers while also changing trichome abundance and cannabinoid concentration in the treated tissues.

Those observations do not establish that the resulting offspring will have lower cannabinoid content. Seed performance and inherited effects were not tested. Equally, increased cannabinoid concentration in female-like flowers on male plants does not establish improved commercial productivity.

Future evaluations would benefit from measuring three distinct outcomes:

• Cannabinoid concentration in representative floral samples.
• Total cannabinoid yield across the harvested plant.
• Seed performance and consistency in the next generation.

Concentration describes how much compound occurs within a given tissue mass. Whole-plant yield also depends on how much harvestable tissue develops. A more concentrated sample does not automatically represent a more productive crop.

Better Measurements Could Make Cannabis Breeding More Predictable

The study’s greatest promise lies in helping researchers connect plant architecture with chemical measurements. That connection could eventually improve how breeders assess candidate plants and compare developmental responses.

MyCannabis’s coverage of AI-assisted cannabis harvest assessment explores another effort to link observable plant traits with cannabinoid accumulation. A useful next step would be to test whether such monitoring approaches remain accurate when breeding treatments change floral anatomy.

First, however, this experiment needs broader replication. Testing additional THC-dominant, CBD-dominant, and balanced varieties would show how widely the relationships hold. Larger studies could combine comparable developmental stages, whole-plant yield measurements, and analyses of individual glandular cells.

The encouraging result is that flower development provides a measurable connection between plant biology and cannabinoid accumulation. Following that connection could help cannabis breeding become more precise, with progress judged through reproducible chemistry, productive plants, and reliable offspring.

References:

¹ Kim, J., Ha, T. H., Jeong, J. C., Lee, C. Y., Kim, H. J., Lee, D. S., Jeong, Y. J., & Kim, S. H. (2026). Chemical modulation of ethylene responses alters floral organ identity, glandular trichome density, and cannabinoid accumulation in Cannabis sativa L. inflorescences. Industrial Crops and Products, 253, 124613. https://doi.org/10.1016/j.indcrop.2026.124613