Ethylene (C₂H₄) is a simple gas that acts as a plant hormone. It promotes fruit ripening, leaf and flower senescence, abscission, and responses to wounding, flooding and other stress. In cannabis it also promotes female flower development; blocking ethylene signalling pushes female plants to form male flowers.
In practice
That last point is the basis of feminised seed. Silver ions block ethylene receptors, so sprays of silver thiosulfate (STS) or silver nitrate on a female plant induce fertile male flowers (Ram & Sett 1982; Lubell & Brand 2018). Pollen from that reversed female carries no Y chromosome, so the seeds are female.
Ethylene also builds up around stressed or damaged tissue and in closed spaces. Ripening fruit stored with cut material, or waterlogged roots producing ethylene precursors, can speed yellowing and leaf drop.
Ethylene-releasing products are sometimes promoted for "ripening" cannabis faster. Evidence of a quality benefit in cannabis is thin. Treat as Contested and keep it off consumable crops unless the data improves.
Don't confuse with
- Ethanol: an alcohol, not a hormone.
- Gibberellin: tends to push toward male expression.
- Abscisic acid: the main drought-stress hormone.
The dry, single-seeded fruit of cannabis that growers call a seed; a hard shell (pericarp plus seed coat) encloses one embryo and does not split open.A female flower with a pistil but no functional stamens; in cannabis, a bract-wrapped ovary topped by two stigmas.A male flower that carries stamens (anthers on filaments) and no functional pistil; in cannabis, five drooping sepals around five pollen-shedding anthers.Feminised seed is seed made by pollinating a female with pollen from another female (or itself) that was chemically reversed, so nearly every seed grows into a female.STS (silver thiosulfate) is a silver compound sprayed on female cannabis to block ethylene action and induce fertile male flowers, the standard method for making feminised seed.Sex reversal is chemically inducing a genetically female cannabis plant to grow fertile male flowers, so its pollen can make feminised seed; silver thiosulfate is the standard agent.Overwatering is watering so often that the medium stays saturated, starving roots of oxygen, which causes drooping, slow growth and root disease.A plant hormone (ABA) that signals water stress, closes stomata and maintains seed dormancy.A family of plant hormones (gibberellins, GA) that promote stem elongation, seed germination and, in cannabis, can shift sex expression toward male flowers.The programmed ageing and breakdown of leaves and other tissues, in which the plant recycles nutrients (especially nitrogen) from old leaves to developing flowers and seeds.In cannabis growing, a plant (usually female) that develops both pistillate and staminate flowers or anthers; botanists call it intersex or monoecious expression.
