Connection between 24hr lights & males

skunkushybrid said:

ok, it's the fully part i'm interested in. You seem to glance over this part and concentrate on hermies which i already know about. I've never heard of a full sex reversal, are there examples?

Click to expand...

I didn't glance over anything and I felt I explained it fairly carefully.

At germination the seed starts out at a pre-determined sex - as determined by the chromosome pairs and gene's it inherits from it's father and mother. As long as nothing interupts that 'genetic program' the plant will grow into whatever sex it was at germination.

However, environmental factors and stress, do and will have an affect on the final sex of that plant and it can reverse its sex either fully or partially depending on environmental factors.

I'm not saying it will reverse its sex and I'm not saying it won't reverse its sex either fully or partially - that is totally and wholly dependant on the environmental factors the plant grows in. There's no reason to assume that if the environment the plant grows in is stress free and as close to optimum as possible that any sex reversal will take place.

ThE sAtIvA hIgH said:

one question i do have (not sure if its been raised ) how come ive grown a pack of fem seeds all in the exact same conditions but only had one hermie ,why did nt they all turn hermie as they were all growing in the same enviroment ?

Click to expand...

I felt I covered this in what I wrote.

Because with feminised seeds, the higher ratio of hermaphrodites (than standard seeds) is almost soley due to those seeds being produced from hermaphrodite parents, so the chromosomes the seed receives is either female or hermaphrodite - not male.

So the hermaphrodites produced from feminised seeds tend to be genetic ones rather than environmentally influenced ones - hence your low occurence - it's probably not being influenced by the environment.

yeah thanks babygrow ...i re read what u had put after i posted lol it makes sense to me .

research photo-periods at overgrow, there is an article there with enough info to get started, then you will be in the same boat I am, wondering when the plant stops storing incoming light energy.

babygro said:

I didn't glance over anything and I felt I explained it fairly carefully.

At germination the seed starts out at a pre-determined sex - as determined by the chromosome pairs and gene's it inherits from it's father and mother. As long as nothing interupts that 'genetic program' the plant will grow into whatever sex it was at germination.

However, environmental factors and stress, do and will have an affect on the final sex of that plant and it can reverse its sex either fully or partially depending on environmental factors.

I'm not saying it will reverse its sex and I'm not saying it won't reverse its sex either fully or partially - that is totally and wholly dependant on the environmental factors the plant grows in. There's no reason to assume that if the environment the plant grows in is stress free and as close to optimum as possible that any sex reversal will take place.

Click to expand...

Why would a plant need to fully change when changing into a hermie would suffice? I have never heard of a full change, and it doesn't make sense that a male plant would turn into a full female when turning into a hermie would guarantee it's pollination and the pollination of the plants immediately surrounding it. To change a genetic code so strikingly merely by changing environmental factors seems far-fetched.

I need more info' on this subject, there really is no need to repeat yourself.

the thing is i thought about everything in this thread and although i find it very interesting i still know ,if i plant 10 normal seeds some of them are going to be female no matter what conditions they are in .

ThE sAtIvA hIgH said:

the thing is i thought about everything in this thread and although i find it very interesting i still know ,if i plant 10 normal seeds some of them are going to be female no matter what conditions they are in .

Click to expand...

We are talking about stress. The type that you'd never do for fear of hermaphroditing your crop. It is being said that not only can you hermy a plant but reverse it's sex completely.

yeah and what im saying is ....before i knew any of this info i planted seeds ....be them fem or normal seeds and allways got good results ..ive used lots of different soils and set ups and its never changed a thing no matter how acidic etc the soil ive used has allways produced males and females .
the thing i dont get is someone says oh ive got 90percebnt females from using this method etc lol just coz u got ten seeds does not mean you have 5 females u could pick up 10 seeds and get ten males no matter what conditions they are in .
so imo it dosent really matter if u just plant 10 normal; seeds the odds are ur gonna get a female

Review Article

Labile sex expression in plants

HELENA KORPELAINEN a1
a1 Department of Biosciences, Division of Genetics, P.O. Box 56, FIN-00014 University of Helsinki, Finland

Abstract

The range of environmental sex determination and sex changes throughout plant taxa from bryophytes and pteridophytes to spermatophytes is reviewed. Lability in sex expression occurs in many plant taxa but only in homosporous pteridophytes is labile sex the rule. Among angiosperms, labile sex appears to be more common among dioecious and monoecious plants than among hermaphrodites. However, hermaphrodites can control allocation to male and female functions by varying the relative emphasis on pollen and ovules. A majority of plants with labile sex expression are perennials, which indicates that flexibility in sex is more important for species with long life cycles. Environmental stress, caused by less-than-optimal light, nutrition, weather or water conditions, often favours maleness. The extreme lability in the sex expression of homosporous pteridophytes is suggested to be related primarily to the mating systems.
(Received February 27 1997)
(Revised September 12 1997)
(Accepted October 30 1997)

Key Words: labile sex; adaptation; Bryophyta; Pteridophyta; Spermatophyta.



back to top



Still can't find anything about completely changing the sex of a plant by using alternate environments.

_uacct = "UA-31379-6";urchinTracker();

doesnt really matter though as if you buy a pack of normal seeds you are bound to geta female unless u are really unlucky ,ive never alterd the growing conditions ive planted in and ive had very mixed results ,so if all of a sudden i got 9 out of ten females id put it down to luck .ill just carry on the way i am and if one day i get 10 out of 10 females ill be happy but i know the next grow icould just as easily get ten males .

And if you used these suggestions and repeatedly got 9 out of ten being females, that would mean.......what?
Peace

well to be honest i think we have all grown in those conditions before now any way except for the high n and p levels ,and i dont fancy giving young plants big doses of n and p as we all know this can cause lots of damage .

videoman40 said:

And if you used these suggestions and repeatedly got 9 out of ten being females, that would mean.......what?
Peace

Click to expand...

Those suggestions are for feminised seed videoman, you need to reread your own link.

Dutch Passion Feminised Seeds (text taken from Dutch passion "feminized seeds")
We are now happy to offer Dutch Passions excellent range of feminized cannabis seeds which include indoor cannabis seeds, indoor/greenhouse pot seeds, Outdoor cannabis seeds, outdoor/greenhouse pot seeds and outdoor/indoor marijuana seeds
In an experiment done in 1999 we grew 15 varieties of "feminized" seeds. We started with 30 seeds per variety. The goals were: 1) to determine the percentages of female, male, and hermaphroditic plants. 2) to compare the uniformity (homogeneity) among plants from "feminized" seeds with those grown from "regular" seeds.
1. The results were excellent. Nine out of fifteen varieties had 100% female offspring. Percentages of female plants from the other 6 varieties were between 80 and 90%. These plants were all hermaphrodites, producing their male flowers at the end of their lifecycle. Seed-setting hardly took place. No males were found.
2. Approximately 70% of the plants of varieties grown from "feminized" seeds were far more uniform than plants grown from "regular" seeds of the same variety. About 20% of the varieties were a little more uniform, while in 10% of the varieties no difference in uniformity was seen.
DUTCH PASSION SEED


From literature and our own findings it appears that the growth of a male or female plant from seed, except for the predisposition in the gender chromosomes, also depends on various environmental factors.
The environmental factors that influence gender are:

• a higher nitrogen concentration will give more females
• a higher potassium concentration will give more males
• a higher humidity will give more females
• a lower temperature will give more females
• more blue light will give more females
• fewer hours of light will give more females

It is important to start these changes at the three-pairs-of-leaves stage and continue for two or three weeks, before reverting to standard conditions.
To produce our feminized seeds, we start with selected female clones. Under standard conditions these female clones do not produce any male flowers. By the method we found, we are able to have these female clones produce abundant male flowers and pollen (see photos). The pollen thus produced we use for the production of our "feminized" seeds.

I understand section 1 and 2 are referring to femenized seeds, just as it is clear to me that the middle section is referring to regular seeds.
Peace

skunkushybrid said:

I need more info' on this subject, there really is no need to repeat yourself.

Click to expand...

Fair enough, it is reasonable to be sceptical about what you read on here, I know I am with a lot of information posted here. I think it's best you simply read the article I read and form your own conclusions and the reason I didn't post it earlier is because I simply couldn't find it - I still don't know where it's from because I cut and pasted it from a web article I found.

Hopefully this will give you all the information you need.

GENETICS AND SEX IN CANNABIS

Sex is an inherited trait in Cannabis, and can be explained in much the same terms as human sexuality can. Like a human being, Cannabis is a diploid organism: its chromosomes come in pairs. Chromosomes are microscopic structures within the cells on which the genes are aligned. Cannabis has 10 pairs of chromosomes (n=10), for a total of 20 chromosomes (2m=20).

One pair of chromosomes carries the primary genes that determine sex. These chromosomes are labelled either X or Y. Male plants have an XY pair of sex chromosomes. Females have XX. Each parent contribute one set of 10 chromosomes, which includes one sex chromosome, to the embryo. The sex chromosome carried by the female ovule can only be X. The one carried by pollen of the male plant may be either X or Y. From the pollen, the embryo has a 50/50 chance of receiving an X, likewise for Y; hance, male and female progeny appear in equal numbers (in humans, the sperm carries either an X or a Y chromosome.)

Sexual Variants in Cannabis
Cannabis has been studied for many years because of its unusual sexuality. Besides the normal dioecious pattern, where each plant bears exclusively male or female flowers, it is not uncommon for some plants to have both male and female flowers. These are called hermaphrodites, or monoecious plants, or intersexes. Hermaphroditic plants form normal flowers of both sexes in a wide variety of arrangements, in both random and uniform distributions.

Natural Hermaphrodites
Some hermaphrodites seem to be genetically determined (protogenous). That is, they naturally form flowers of both sexes given normal growing conditions. Possibly genes carried on the autosomes (the chromosomes other than the sex chromosomes) modify the normal sexual expression. Monoecious varieties have been developed by hemp breeders in order to ensure uniform harvests.

It is also possible that these particular are polyploid, which means they have more than the usual two sets of chromosomes. This kind of hermaphrodite may have XXY (triploid), or XXYY or XXXY (tetraploid) sex chromosomes. However, no naturally occurring polyploids have ever been verified (by observation of the chromosomes) in any population of Cannabis. Polyploids have been induced in Cannabis by using mutagens, such as the alkaloid colchicine.

Whatever then genetic explanation may be, one or more of these natural hermaphrodites may randomly appear in any garden. They are sometimes faster-maturing, have larger leaves, and are larger in overall size than their unisexual siblings. They usually form flowers of both sexes uniformly in time and distribution, and in some unusual patterns. For example, from Mexican seed, we have seen a plant on which separate flowering cluster consisted of both female and male flowers: and upper section of female flowers had upraised stigmas, and a lower section of male flowers dangled beneath the female flowers. In other plants from Mexican seed, the growing tips throughout the plant have female flowers; male flowers sprout from the leaf axils along the main stem and branches. Plants from "Thai" seed sometimes form male and female flowers on separate branches. Branches with female flowers tend to predominate, but branches having mostly male flowers are located throughout the plant.

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.

continued

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.

Thanks a lot babygro very informative.

So sex reversal can only happen during the flowering period, and then it's not a guarantee. To say that you can guarantee a 90% female ratio from normal seed is wrong.

babygro said:

Environmental Effects
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.

Click to expand...

Sounds like from this article or research, that going with a 24/7 lighting schedule during the veg. stage helps produce more females. This probably requires the right type of light/bulb type (MH) to shorten the veg. period. Interesting how the two studies differ in this aspect.

I'm still a little bit skeptical... but less than I was when I first read this.

Cannabis - Wikipedia, the free encyclopedia

Granted wikipedia is not the end-all, but apparently this behavior is apparent in other plants, so this isn't complete bullshit. I'd like to see some sort of credible research done (other than someone planting ten plants and getting a good ratio), but I don't think that's going to happen any time soon. It's probably a good idea, anyway, to follow these guidelines as they at least seem to help.