Once and for all, is sex predetermined?

[cosmokramer421]

There is substantial scientific evidence taht says the sex of the marijuana plant is predetermined in the seed. A seed is set to either turn out to be a male, female or female which then hermies. But I read all over forums that there are ways to increase the chance of females. I'm pretty sure this is all bullshit, and there is absolutely no way to increase the chance of females, because it is all predetermined from seed. Is there any scientific evidence that claims that marijuana seeds are not predetermined in sex, and that the sex can be altered by the environment? I'd like to see some real scientific evidence that claims that. I REALLY wish people would quit posting false claims that sex can be affected by environment, with no scientific proof. This probably-false-claim is spreading like the flu, and annoys the hell out of me.

Does anyone have any proof that the sex of a marijuana plant can be changed because of environmental factors (not talking about hermies.)

Has anyone taken clones from an unkown sexed plant to have the clones turn out to be different sex? I've never heard of that happening, so that sort of proves that sex is predetermined.

Does anyone know of any information from a reputable source that claims that sex can be changed by environment? And by reputable source, I don't mean Joe Schmo grew 10 plants in poor conditions and 8 turned out to be male. That only proves that he had 8 out of 10 seeds that were predetermined male, and joe schmo is unlucky.

And please don't respond with "do some research, noob." or "read the stickies, moron"

[chunkdaddyo]

Hey cos.....I too subscribe to the belief that the sex is determined genetically at the RNA and DNA level. I know that a lot of folks here believe that putting a seed in proximity to a ripening banana will magically turn out females, and truth be told, it probably doesn't hurt to try it. However, I just don't believe that a gas known to cause ripening and eventual decay, will cause a genetic mutation in a seed. Science has proven that sex is determined on a molecular level, and once a seed is created from the combination of xx/xy chromosomes, the seed will be what nature intended it to be.

I do have an open mind however, and I too, would really like to see any kind of scientific data that has been written on this subject. I have Googled ethylene gas and so far all I have found is information on ripening fruits and veggies. If anyone does have a link to any data, please post it.

[amoril]

here ya go

Ed Rosenthal and Mel Frank have this to say on the topic ::

"Abnormal Flowers, Intersexes, Reversals


Gender is set in the new plant at the time of fertilisation by its inheritance of either the X or the Y chromosome from the male (staminate) plant. With germination of the seed, the environment comes into play. Heritage sets the genetic program, but the environment can influence how the program runs. (Sexual expression in Cannabis is delicately balanced between the two.) The photoperiod, for example, controls the plant's sequence of development. Also, the plant's metabolism and life processes are dependent on growing conditions. When the environment does not allow a balance to be maintained, the normal genetic program may not be followed. This is mirrored by abnormal growth or sexual expression.

Abnormal Flower : Abnormal sexual expression includes a whole range of possibilities. Individual flowers may form abnormally, and may contain varying degrees of both male and female flower parts. For instance, a male flower may bear a stigma; or an anther may protrude from the bracts of a female flower. Abnormally formed flowers are not often seen on healthy plants, although if one looks hard enough, a few may be found in most crops. When many of the flowers are abnormal, an improper photoperiod (coupled with poor health) is the most likely cause. Abnormal flowers sometimes form on marijuana grown out of season, such as with winter or spring crops grown under natural light.


Intersexes and Reversals Much more common than abnormally formed flowers is for the plant's sex to be confused. One may find an isolated male flower or two; or there may be many clusters of male flowers on an otherwise female plant, or vice versa. These plants are called intersexes (also hermaphrodites or monoecious plants). Intersexes due to environment causes differ from natural hermaphrodite in having random distributions and proportions of male and female flowers. In more extreme cases, a plant may completely reverse sex. For example, a female may flowers normally for several weeks, then put forth new, sparse growth, typical of the male, on which male flowers develop. The complete reversal from male flowering to female flowering also happens.

All other things being equal, the potency of intersexes and reversed plants is usually less than that of normal plants. If there are reversals or intersexes, both of the sexes will usually be affected. Female plants that reverse to male flowering show the biggest decline. Not only is the grass less potent, but the amount of marijuana harvested from male flowers is negligible compared to the amount of marijuana that can be harvested from a normal female. Plants that change from male to female flowering usually increase their potency, because of the growth of female flower bracts with their higher concentration of resin. Female flowers on male plants seldom form as thickly or vigorously as on a normal female. Between the loss in potency and the loss in yield because of females changing to males, a crop from such plants is usually inferior, in both yield and potency, to one from normal plants.


Environmental Effects


Many environmental factors can cause intersexes and sexual reversals. These include photoperiod, low light intensity, applications of ultraviolet light, low temperatures, mutilation or severe pruning, nutrient imbalances or deficiencies, senescence (old age), and applications of various chemicals (see bibliography on sex determination).


The photoperiod (or time of planting using natural light) is the most important factor to consider for normal flowering. In 1931, J. Schaffner (105) showed that the percentage of hemp plants that had confused sexual characteristics depended on the time of year they were planted. Normal flowering (less than five percent of the plants are intersexes) occurred when the seeds were sown in May, June, or July, the months when the photoperiod is longest and light intensity is strongest. When planted sooner or later in the year, the percentage of intersexuals increased steadily, until about 90 percent of the plants were intersexual when planted during November or early December.


Marijuana plants need more time to develop than hemp plants at latitudes in the United States. Considering potency, size, and normal flowering, the best time to sow for the summer crop is during the month of April. Farmers in the south could start the plants as late as June and still expect fully developed plants.


If artificial light is used, the length of the photoperiod can influence sexual expression. Normal flowering, with about equal numbers of male and female plants, seems to occur when the photoperiod is from 15 to 17 hours of light for a period of three to five months. The photoperiod is then shortened to 12 hours to induce flowering. With longer photoperiods, from 18 to 24 hours a day, the ratio of males to females changes, depending on whether flowering is induced earlier or later in the plant's life. When the plants are grown with long photoperiods for six months or more, usually there are at least 10 percent more male then female plants. When flowering is induced within three months of age, more females develop. Actually, the "extra" males or females are reversed plants, but the reversals occur before the plants flower in their natural genders.


Some plants will flower normally without a cutting of the photoperiod. But more often, females will not form thick buds unless the light cycle is cut to a period of 12 hours duration. Don't make the light cycle any shorter than 12 hours, unless the females have not shown flowers after three weeks of 12-hour days. Then cut the light cycle to 11 hours. Flowers should appear in about one week.


Anytime the light cycle is cut to less than 11 hours, some intersexes or reversed plant usually develop. This fact leads to a procedure for increasing the numbers of female flowers indoors. The crops can be grown for three months under a long photoperiod (18 or more hours of light). The light cycle is then cut to 10 hours. Although the harvest is young (about five months) there will be many more female flower buds than with normal flowering. More plants will develop female flowers initially, and male plants usually reverse to females after a few weeks of flowering.


Of the other environmental factors that can affect sexual expression in Cannabis, none are as predictable as the photoperiod. Factors such as nutrients or pruning affect the plant's overall health and metabolism, and can be dealt with by two general thoughts. First, good growing conditions lead to healthy plants and normal flowering: female and male plants occur in about equal numbers, with few (if any) intersexes or reversed plants. Poor growing conditions lead to reduced health and vigour, and oftentimes to confused sex in the adult plant. Second, the age of the plants seems to influence reversals. Male plants often show female flowers when the plant is young (vigorous) during flowering. Females seven or more months old (weaker) often develop male flowers after flowering normally for a few weeks.


Anytime the plant's normal growth pattern is disrupted, normal flowering may be affected. For instance, plant propagated from cuttings sometimes reverse sex, as do those grown for more than one season."


bodda bing

[Afghan#1]

I'm pretty certain hermies prove that sex is not predetermined.Marijuana is similar to other organisms like clownfish.Clownfish are always born male and the largest dominate fish of a mated pair will change into a female.

http://en.wikipedia.org/wiki/Clownfish

[amoril]

if sex is not predetermined, at least to a certain degree, then what do you propose is the reason for the reported 50/50 male female average ratio from seed?

and, over time, youll see that it really is damn close to 50:50 with regular seeds.

notice that the clownfish will sexually mature based upon a stimulus, so whats the stimulus in cannabis?

....its predetermined, but environment can effect this representation

[Afghan#1]

Originally Posted by amoril

if sex is not predetermined, at least to a certain degree, then what do you propose is the reason for the reported 50/50 male female average ratio from seed?

and, over time, youll see that it really is damn close to 50:50 with regular seeds.

notice that the clownfish will sexually mature based upon a stimulus, so whats the stimulus in cannabis?

....its predetermined, but environment can effect this representation

Thats a very good question.Considering it's illegal i would'nt expect very much scientific research on the subject any time soon.All we have is anecdotal evidence to go on.There are a few things i've noticed over the years,though.I always grow outside and always get 80-90% females on pure indica plants.The males are almost always the runt or the plant that gets chewed up by critters.When i grow sativa it's always the biggest plant that turns male (the complete opposite of indica).I have no idea why,but thats been my experience so far.

[Klutter]

Originally Posted by Afghan#1

Thats a very good question.Considering it's illegal i would'nt expect very much scientific research on the subject any time soon.All we have is anecdotal evidence to go on.There are a few things i've noticed over the years,though.I always grow outside and always get 80-90% females on pure indica plants.The males are almost always the runt or the plant that gets chewed up by critters.When i grow sativa it's always the biggest plant that turns male (the complete opposite of indica).I have no idea why,but thats been my experience so far.

You are sadly mistaken. It is illegal in the US. Amsterdam has a fucking Cannabis COLLEGE. Rosenthal knows his shit, as does Jorge - and both agree on the pre-sexing issue.

The US is NOT the 'world'.... very small piece of it to be honest....