What causes a pre-disposition for a plant to become male?

Thompson3600 said:

I've heard things such as high temperatures, acidic soil, not having enough plants around that are also female, etc. but yet cannot find a comprehensive list with explanations of any. Please add your insight and explanations so we can form a comprehensive list.
Thank you

Click to expand...

The part about not having enuff other "female" plants around is completely bullshit.. sorry but as soon as i read that part it kinda pissed me off someone is saying that.. one other way that could cuz such an effect would be light leaks during flowering.. I wanna say light leaks are more comon the causes but im sure others will post their experience

I've seen a lot of rumors, but very little proof on any of it (pH, temp, etc).

I do recall a well-written article on ICMAG that argued that stresses of any kind (pH, temp, too much / too little water, nutes, etc) during the 3rd/4th week of growth was a critical factor, and that having your groove down with your plants by week 3 was a key factor in getting more females. The author was claiming something like an 80% female ratio by focusing on this idea. But again, no controlled trial info or other data you can really lock in on.

I'm surprised that no one in the whole world has cracked into the MJ genome to see how clearly the genetic predisposition is defined inside the seed.

Let's get one thing clear, are you asking:
A. What makes a seed pre-disposed to be male (or female) in the first place?
-or-
B. What environmental factors can change the pre-disposition of a seed by altering the ultimate (final) sexual outcome?

In case you are asking question A. - I haven't got a clue! But to answer question B. - here is something that makes it easy to understand. I Cut & Pasted from Meangreen @ hipforums.

INCREASING YOUR CHANCES OF FEMALES
A well maintained grow room with plants growing in optimal conditions will naturally produce more females than males. There are some other things you can do to increase your odds of improving your male to female ratio. These are as follows:
• High nitrogen levels in vegetative growth have shown to produce more females than males. This might be a good to reason to use feeds with a higher l\l to P and K ratio rather than foods with an equal N to P and K ratio. Remember though that plant burn will only lead to stress and this will produce more males and hermaphrodites than females.

[FONT=Times New Roman, Times, serif]• High potassium levels in vegetative growth and flowering tends to produce more males than females. Keeping your potassium levels down is another good reason to choose a food with a higher N than P and K ratio where the P and K ratios are even, or where the K ratio is kept lower than P. Remember though that lack of K can cause plant stress due to this nutrient deficiency and this can cause more males and hermaphrodites to appear than females.
• Cannabis plants grow best under conditions of between 40 and 80 percent relative humidity (rH). In the higher rH range of between 70 and 80 your female to male ratio may increase.
• Cannabis plants grow best at 75 degrees Fahrenheit. If you do not allow the temperatures to increase beyond this you will improve your chances at getting more females than males. If the environment is supplemented with C02 the temperature may be allowed to increase as far as 95 degrees Fahrenheit.
• Using MH lights in vegetative growth will improve your female to male ratio[/FONT]
_______

Not using a clone.