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I was searching for uses of pollination during crop steering when I came across a recently published cannabis study regarding pollination and cosexuality. I was delighted to see universities beginning to study genetic markers in the cannabis sexes, especially beyond how to increase yields through replicating feminized seed.

Cannabis boasts a fascinating plant ability: it can switch its reproductive roles, producing both male and female traits. This flexibility, known as sexual lability, emerges naturally in stressful conditions such as crop steering through regenerative and vegetative responses or can be induced chemically. This trait has been pivotal in the cannabis industry, particularly in the production of feminized seeds ensuring optimal yield. 

Using pollination to influence crop steering involves strategically managing pollination to optimize crop yield and quality. Pollination is a crucial step in the reproduction of many crops, as it facilitates the transfer of pollen from male to female flower parts, leading to fertilization and seed development.

To influence crop steering through pollination, farmers ensure that pollination occurs during the optimal growth stage of the crop. This requires understanding the flowering patterns and peak pollination periods for specific crops. I've seen organic farms who employ natural pollinators like bees, butterflies, and other insects, or even using managed pollination services, can enhance the efficiency of the pollination process. Some indoor crops benefit from cross-pollination, where pollen is transferred between different plants of the same species. This can sometimes result in increased genetic diversity and improved yield but can be tricky. In certain cases, controlling the pollination process may be necessary. This can involve measures such as isolating specific plants or varieties to prevent unwanted cross-breeding. Consider environmental conditions such as temperature, humidity, and wind speed, as they can impact pollination success. Implementing measures to mitigate adverse weather effects can optimize crop steering.

By strategically managing pollination, farmers can influence the direction of crop growth, ensuring better yields and improved crop characteristics.

Why does this matter? 

Well, this dual reproductive nature offers advantages. Cosexual plants can self-pollinate and engage in cross-pollination, maximizing their genetic contributions to future generations. However, this versatility comes with challenges. In resource-limited scenarios, investing in one reproductive function often hampers the other, leading to potential fitness trade-offs.

Unlike most plants, cannabis displays both unisexual and cosexual traits, relying on genetic sex determination through specific chromosomes. 

But here's the catch: 

Historical restrictions on cannabis research have severely limited our knowledge, especially regarding male cannabis plants and their competitive dynamics, particularly at the pollen stage. In the US no such studies are funded by the government at this time. Recognizing the cannabis industry's heavy reliance on feminized seeds and the potential competition among male plants during pollen production, Canadian researchers embarked on a study. 

Their goal?

 To discern differences in pollen characteristics between unisexual males and cosexual plants. Preliminary findings suggest potential variances based on the plant's origin of cosexuality (whether natural or induced). In essence, delving into Cannabis sativa's reproductive intricacies not only enriches our botanical understanding but also holds significant implications for a cannabis industry worth billions.

The study compared the flowering patterns of three groups of cannabis sativa plants: unisexual males, drought-induced cosexuals, and chemically induced cosexuals. Unisexual males flowered earlier and for a longer duration than both types of cosexual plants. Chemical induction altered the flowering behavior unnaturally. Flowering patterns also had correlations with pollen characteristics. Pollen abundance, non-abortion rates, and viability showed various correlations with the timing aspects of anthesis (start, duration, and end).

The study investigated pollen characteristics across different reproductive phenotypes of Cannabis sativa: unisexual males, drought-induced cosexuals, and chemically induced cosexuals.

1. Pollen Abundance: 

   - Whole-plant pollen abundance significantly differed among the groups. 

   - Unisexual males produced 223% more pollen than both types of cosexual plants, which had similar pollen abundance levels.

   - Individual flower pollen abundance did not show significant differences among the reproductive phenotypes.

2. Pollen Non-Abortion Rates:

   - Though pollen non-abortion rates showed marginal differences among the groups, post-hoc analysis revealed no significant variances. 

   - All reproductive phenotypes had similar non-abortion rates.

3. Pollen Viability:

   - Significant differences were observed in pollen viability among the reproductive phenotypes.

   - Unisexual males and drought-induced cosexual plants had pollen with 200% higher viability than chemically induced cosexual plants.

The study found that unisexual male cannabis sativa plants flowered earlier and for a longer duration compared to both chemically induced and drought-induced cosexual plants. Pollen production and viability were closely linked to the flowering characteristics. While unisexual males produced significantly more pollen at the whole-plant level, there was no significant difference at the individual-flower level. The study suggests that the higher pollen production in unisexual males supports the idea that cosexual plants may have to divide resources between male and female gamete production, potentially reducing their efficiency. Notably, chemically induced cosexual plants exhibited lower pollen viability, possibly due to the effects of colloidal silver treatments, which are known to influence the development of a cosexual phenotype. However, the study acknowledges limitations such as using a single cultivar, which might not represent broader cannabis strains, and the need for further research with varied chemical treatments and environmental conditions to understand male reproductive traits better in cannabis sativa.

Source: Wizenberg SB, Muir-Guarnaccia J, Campbell LG. Cosexuality Reduces Pollen Production and Fitness in Cannabis sativa L. Plants. 2023; 12(21):3731.


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