Pollen from hermaphroditic flowers can fertilize, study shows

Could pollen from hermaphroditic cannabis flowers fertilize female flowers? It seems to defy what we have long believed, but a team of Canadian researchers has found some intriguing results.

To fully appreciate the significance of the findings, you have to understand basic cannabis reproductive biology.

Cannabis is dioecious, meaning that male and female flowers are usually found on different plants.

Cultivation of cannabis focuses on female plants because the trichomes of unfertilized female flowers synthesize the highest levels of cannabinoids and terpenes.

Unfortunately for commercial growers, hermaphroditic plants – that is, those that have flowers containing both male and female reproductive organs – can arise spontaneously, leading to seed production and greatly reduced essential oil content.

It is believed that hermaphroditism arises as a means to produce seeds when a plant senses less-than-ideal conditions for its survival. There are genetic and environmental factors involved in the development of hermaphrodites, including physical or chemical stressors.

A key stress is the interruption of the normal 12-hour dark photoperiod that is used to encourage plants to flower. Hermaphroditic flowers can also result when temperatures are either too high or too low.

The Canadian researchers studied hermaphroditism in indoor-grown commercial cultivars of cannabis.

Their study, published in Frontiers in Plant Science, used rooted cuttings grown in commercial indoor facilities under industry-standard conditions that maximized the development of female flowers.

The authors found that male reproductive organs (anthers) were found in 5%-10% of the plants examined. Rarely was an entire flower converted to clusters of anthers.

This is the first report that pollen from hermaphroditic flowers, while making much less pollen than the flowers of male plants, can fertilize female flowers and lead to the production of viable seeds.

Interestingly, all the seeds collected from hermaphroditic flowers produced female plants, which is not the case for seeds that come from cross-fertilized plants.

Commercial cultivators rely on cuttings from female mother plants as these are genetically identical to the mother plant and develop only female flowers.

If cultivation uses seed-grown plants, any males are destroyed to prevent pollination of the female plants.

When male plants are excluded from a grow room, as is the case in commercial cultivation, it is likely this spontaneous development of hermaphroditic flowers is what is responsible for low-level seed production.

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