Sex of plants defined from the seed or not?

[SUPER_HAZE]

Hello friends.
Years ago I read that depending on the environment and growing conditions when defining the sex, more males or more females would come out.
Then I read here that sex is already defined from the time it is a seed.
I have had 30 panama females of 30 regular seeds. From old timers haze a variety that few males come out I have had about 60% males.
What do you think?

 

[goingrey]

Many studies suggested that in hemp, epigenetic mechanisms could be associated with the control of sex determination, besides genetic factors [reviewed in Truta et al. (2007)]. The phenotypic outcome of sex expression in hemp might be controlled at the transcriptional- or post-transcriptional level, so without alterations in the DNA or affecting chromatin structures (Soldatova and Khryanin, 2010). The studies confirmed the role of endogenous phytohormones in the regulation of genetically determined sex type, as well as the possibility to modify it by exogenous external factors, which include ions, phytohormonal treatments, environmental factors such as photoperiod, etc [reviewed in Truta et al. (2007)]. The external factors exert a strong modifying effect, especially on the sex expression of monecious plants, in which both staminate and pistillate flowers are induced, in different proportions. The accumulation of Cu++ and Zn++ ions with zeatin induce feminization, whereas the accumulation of Pb++ ions favors a masculinization effect (Chailakhyan and Khryanin, 1978; Freeman et al., 1980; Galoch, 2015). The phytohormones gibberellins, auxins, ethylene and cytokinins play a role on the expression of sex in many monecious and diecious systems (Truta et al., 2007). Generally, auxins and ethylene have feminizing effects (Heslop-Harrison, 1963; Galoch, 1978), whereas cytokinins and gibberellins have masculinizing effects, though contrasting effects have been observed for some species and experimental conditions [reviewed in Ainsworth (2000)]. For example, Chailakhyan and Khryanin (1978) and Galoch (1978), cited by Dellaporta and Calderon-Urrea (1993) also reported feminizing effects of 6-benzylaminopurine (cytokinin) in species of Vitis, Spinacia, and Cannabis. In species such as Mercurialis annua and Arabidopsis thaliana, auxins induce expression of genes which exert a direct control on the biogenesis of sexual organs. Examples of such auxin regulated genes are auxin responsive factor genes (arf genes) in tomato, arabidopsis and papaya, which are transcription factors that control female flower development [reviewed in Li et al. (2016)]. It is possible that the gibberellins act as repressors of female flower development. The ratio of the different phytohormones is very important in the phenotypic sex expression in hemp (Truta et al., 2007). Gibberellins are for instance known to promote masculinization in spinach [reviewed in Salentijn et al. (2019)]. West and Golenberg (2018) reported that external treatment of gibberellic acid (GA) in spinach affected the expression of the gibberellic acid insensitive gene (gai gene), which is a transcription factor of the DELLA family. The gai gene is highly expressed in female inflorescences. GAI transcription factor is a repressor of the expression of B-class homeotic genes, which are masculinizing factors. B-class genes stimulate male organ formation and simultaneously supress the development of female organs in the flowers. This study in spinach concluded that high levels of exogenous GA inhibit the expression of gai gene, which consequently release inhibition on the masculinizing factors. Furthermore, the effect of photoperiod on sex determination of hemp could be associated with the external regulation of GA biosynthesis by differences in light quality and daylength (Hedden and Phillips, 2000). Schaffner (1921) reported that female hemp plants grown under low light winter conditions produced male flowers, while those plants grown under spring normal conditions did not produce male flowers. Another environmental factor is the soil quality. For example, a nitrogen-rich nutrition induces masculinization [reviewed in Truta et al. (2007)].

Frontiers | Genetic Architecture of Flowering Time and Sex Determination in Hemp (Cannabis sativa L.): A Genome-Wide Association Study

Flowering time and sex determination in hemp (Cannabis sativa L.) strongly influence fiber quality and seed production of this crop. The control of these tra...

www.frontiersin.org

What do I think? I think sex is determined at conception. It's possible in some cases one sex may have an advantage during conception. Maybe even during germination which could result in 100% of a certain sex (but a 50% germination rate). And obviously chemicals/stress can cause a reversal, not even taking into account genetic hermies.

The theories about light color or whatever changing sex I don't believe. I'm happy to change my mind with enough proof and a reasonable explanation but have not such a thing yet.