Cannabis Sativa L: Sex differentiation

Cannabis Sativa L: Sex differentiation

This part of the research is dedicated to scientific data on cannabis sex differentiation.

Sex determination

Cannabis Sativa L are dioecious species, which mean that there are male and female plants. Only 7% of all known to us plants are dioeious and sex is determined by X and Y chromosomes. However, some cannabis plants could be monoecious (or hermaphrodite). [1,2]

cannabis-sexes
Dioecious cannabis plants develop in separate male and female plants

Male and female plants can be identified via microscopic method as soon as the leaves of the fourth node emerge. [3]

Human genome illustrates differences between autosomes and sex chromosomes.
Human genome illustrates differences between autosomes and sex chromosomes.

Cannabis Sativa L genome is composed of 9 pairs of autosomes (not sexual chromosome) and 1 pair sexual chromosomes (X and Y). But X and Y chromosomes are not the only components responsible for sex determination. The research shows that sex is determined by the ratio of X chromosome and autosomes rather than an active Y chromosome. This means that presence of Y chromosome does not constitute male plant. [3]

Origin and theory for sex determination of hermaphrodite cannabis plants

Monoecious cannabis plant (hermaphrodite) express both male and female flowers
Monoecious cannabis plant (hermaphrodite) express both male and female flowers

Monoercious (or hermaphrodite) varieties were observed as well and it was identified that this is a recessive trait. Hemp producers prefer hermaphrodite plants because of higher seed yield, higher crop homogeneity and easier harvest. However, sexual phenotype of monoercious plants is not stable. Maintaining hermaphrodite plants require strict selection otherwise they will reverse back to male and female plants. Sex determination of hemp is also affected by external factors such as hormonal treatments, photoperiod or nitrogen status. The sex determination of monoercious plants is not clear. According to one theory there are XX, XY and YY forms and hermaphrodite plants have XX. Other studies claim that there is no specific chromosome type and they suggest that hermaphrodite plants are result of single gene mutation. [3]

First autoflowering cannabis breeders

Russian scientists, Grishko and Malusha (1935) and Grishko et al. (1937) were the first to breed monoecious (hermaphrodite) and autoflowering dioecious hemp varieties back in the 30s. Grishko discovered that dioecious plants could be bred to hermaphrodite varieties and using inbreeding they can create new varieties. [6]

Sex reversion in cannabis

Cannabis Sativa L allows total or partial reversion of the sex. For example, female plants can be reversed to male plants by using chemicals like aminoetoxyvinlglycine, silver thiosulphate and silver nitrate, which inhibit ethylene biosynthesis. Male plants can be reversed to female by using ethephon, activator of ethylene biosynthesis. [1]

Cannabis cloning

It is known that Cannabis Sativa L could be maintained by using clones. However, prolonged usage of clones could lead to genetic mutations also known as somaclonal variations (chromosomal rearrangements). Some of these somaclonal variations could be easily revered back unless they are specifically selected to be preserved. In order to avoid somaclonal variations the plants should be monitored closely. Axillary bud proliferation is considered the most suitable and used method for plant micropropagation. [2, 5]

There are different cannabis cloning techniques and they follow strict protocols
There are different cannabis cloning techniques and they follow strict protocols

Unfortunately sex determination in Cannabis Sativa L is not simple. Although sex determination is genetic, there are also environmental factors that could influence sex determination. [4]

Sources

1. The sexual differentiation of Cannabis sativa L.: A morphological and molecular study

2. Biotechnology for Medicinal Plants: Micropropagation and Improvement

3. Sex chromosomes and quantitative sex expression in monoecious hemp (Cannabis sativa L.)

4. Some aspects of sex determinism in hemp

5. Axillary Bud Proliferation Approach for Plant Biodiversity Conservation and Restoration

6. Current status and future scenarios of hemp breeding

0 thoughts on “Cannabis Sativa L: Sex differentiation

  1. jayp says:

    Is there anyway to tell if a plant is female before the white pistils emerge? Both male and female have stipules right? Just trying to find a way to tell faster without having to wait on pistils to form. Thanks for the info. You know i have heard Subcool and some others say that a seed is neither a male or female before it is germed and that you can control this by temp and such. If that was the case then they would always get females and never worry about getting males.I dont beleive this cause i have germed alot of M/F seed and once got over 30 of 40 males to about 10 females and everrything was done in the same fashion.

  2. Lady Stone says:

    Hi jayp, yes, there is a DNA method that could tell if the plant is male or female at early stage but it is not available for everyone, just for licensed hemp companies and producers. It is an expensive test.
    From what I found the environmental conditions can affect plant gender but it is genetic as well, so you cannot use only growth conditions to trigger male or female plants development. There are still lots of questions on sex determination but these are results from the published research now. I am sure there will be more information in the next couple of years.

  3. N.W. says:

    Im a believer in the fact of conditions can affect the sex of a plant.. I have found that too hot over 24c and the ratio is more towards Males and too cold below 18c has a similar effect..
    But even those grown at the range between 18c-24c are still in the lap of the Ganga gods…lol.. I have heard of different methods of trying to predetermine the sex of plants like Stipules jayp mentions i didnt find any credence to it or ripe banana skin because of the chemicals it gives off.. LOL all i got was mouldy seeds…

    Another great article.. Thankyou..

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