Sex reversal is treating a genetically female (XX) plant so that it forms male flowers that shed fertile pollen. Silver ions block the plant's response to ethylene, a hormone involved in female flower development, which lets male flowers form instead (Ram and Sett 1982). Silver thiosulfate (STS) is the standard agent; colloidal silver works on the same principle but is less consistent. Both are generic chemical names.
In practice
Breeders reverse one female, or a branch of her, then use the pollen on other females (a feminised cross) or on the same plant (an S1). The reversed plant's own flowers are not usable bud. Silver compounds are toxic, so treated material is kept out of consumption and handled with gloves; the treatment details are in the main article.
"Rodelization" is a grower term for letting a female run past ripeness in the hope she throws pollen on her own. That deliberately selects for plants that break down into herms, and is not good breeding.
Don't confuse with
- Hermaphrodite: a plant that makes both flower types on its own, from genetics or stress. Reversal is deliberate and controlled.
- Reciprocal cross: swapping parents' roles, a different meaning of "reversed".
Myth check
Only reverse females that have stayed fully female over several runs. Reversing a plant that already herms passes that weakness on. See feminised seed and sex reversal.
A male flower that carries stamens (anthers on filaments) and no functional pistil; in cannabis, five drooping sepals around five pollen-shedding anthers.A gaseous plant hormone that regulates ripening, senescence, stress responses and, in cannabis, female flower expression; blocking it makes females produce pollen.A female flower with a pistil but no functional stamens; in cannabis, a bract-wrapped ovary topped by two stigmas.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.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.S1 is seed from a plant pollinated with its own pollen; every S1 seed is female and a new genotype, not a copy of the parent.In cannabis growing, a plant (usually female) that develops both pistillate and staminate flowers or anthers; botanists call it intersex or monoecious expression.A reciprocal cross repeats a cross with the parents' roles swapped (A × B, then B × A) to test whether the seed parent affects the offspring.Selfing is pollinating a plant with its own pollen, in cannabis usually by reversing part of a female to make pollen; it is the most intense form of inbreeding.Cannabis uses an XY sex determination system: females carry two X chromosomes (XX) and males an X and a Y (XY), so regular seed is roughly half male.
