Foliar Sprays of Silver Thiosulfate Produce Male Flowers on Female Hemp Plants. (Dec 2018).
Female plants are preferred for cannabinoid production because females accumulate, predominantly in the inflorescences, significantly greater cannabinoid content than male plants (Small, 2015).
Rahn et al. (2016) and Soler et al. (2017) report that hemp growers are using hormones or chemicals like STS to make feminized seed, in which 100% of the seed is female.
Mohan Ram and Sett (1982) suggest STS can be used to make male flowers with viable pollen on female hemp plants, but their methods are not directly translatable to commercial applications.
Male flowers induced on genetically female plants will produce pollen containing only X gametes, which when crossed with eggs from female plants result in all-female seed (Mohan Ram and Sett, 1982).
Green (2015) describes using a single foliar spray of STS to produce feminized hemp seed.
This method has been shared among growers online, but this information is not based on scientific research.
There are no published reports about using foliar sprays of STS to produce feminized hemp seed. Therefore, the objective of this work was to evaluate the efficacy and rate of foliar sprays of STS for inducing male flowers and producing female seed for different strains of hemp.
Materials and methods (Extract)
Plants were 6 inches high with two shoots when foliar sprays of STS were initiated.
Silver thiosulfate solutions (0.3 and 3 mM) were prepared by mixing silver nitrate with STS in a molar ratio of 1:4, per Cameron and Reid (1981). Plants were sprayed to runoff (about 20 mL/plant) on three occasions, 7 d apart
Green (2015) suggested that female hemp plants can be masculinized using a single foliar spray of 0.3mM STS, but did not provide any information about the percent conversion to male flowers.
We did not find three foliar sprays of 0.3mM STS to be as effective for producing male flower formation as three foliar sprays of 3 mM STS.
A similar action of ethylene blocking by STS is likely responsible for the production of male flowers on female hemp plants in our study.
It is generally believed that ethylene blocking is extended when a series of sprays of STS is used compared with a single spray of STS (Reid et al., 1980).
Mohan Ram and Sett (1982), using 25 to 100 mg STS applied directly to the growing shoot tip of female hemp plants, were able to produce male flowers.
However, they also noted severe necrosis on young leaves covering shoot tips and suspended apical growth for 20 to 25 d before lateral budbreak and subsequent flower formation.
In comparison, we did not observe any plant phytotoxicity or delay in flower development.
Furthermore, we were able to achieve 95% to 100% conversion to male flowers for all hemp strains, whereas Mohan Ram and Sett (1982) reported 60% to 80% conversion.
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Foliar Sprays of Silver Thiosulfate Produce Male Flowers on Female Hemp Plants.pdf