Understanding Cannabis Reproduction: Dioecious Male/Female vs. Monoecious Hermaphrodite

Cannabis sativa, a versatile plant with various applications, exhibits intriguing reproductive patterns. It can be categorized into two main groups: dioecious plants, which have distinct male and female individuals, and monoecious plants, also known as hermaphrodites, which possess both male and female reproductive structures within a single organism. This article delves into the unique characteristics and implications of each of these reproductive strategies.

Anther Morphology and Pollen Formation

In hermaphroditic inflorescences (structures that bear flowers), the development of anthers (the part of a flower that produces pollen) and the process of pollen formation were similar to those in staminate (male) flowers. This suggests that hermaphrodite plants retain the ability to produce viable pollen, similar to their male counterparts.

Genetic Composition of Seedlings

Seedlings grown from hermaphroditic seeds and anther tissues showed a genetic composition that was characteristic of females. This intriguing phenomenon implies that, despite the presence of male reproductive structures, hermaphrodite plants carry genetic information that predominantly favors female traits.

Cross-Fertilization

Seedlings derived from seeds resulting from cross-fertilization (where pollen from one plant fertilizes the flower of another plant) exhibited a 1:1 ratio of male to female sex expression. This indicates a balanced genetic contribution from both parental plants, resulting in a more even distribution of male and female traits.

Hermaphroditic Seeds

Hermaphroditic inflorescences produced seeds that exclusively gave rise to genetically female plants. This remarkable finding suggests a genetic predisposition towards female traits, even in plants that possess both male and female reproductive organs.

PCR Assays: Unveiling Genetic Markers

Polymerase Chain Reaction (PCR) assays were used to analyze DNA fragments. A 540 base pair (bp) fragment was found in both male and female plants. Additionally, a 390 bp band was exclusively associated with male plants. This indicates a clear genetic distinction between male and female plants, further highlighting the complexity of sex determination in Cannabis sativa.

Retrotransposons: Unearthing Genetic Influence

Sequence analysis of DNA fragments identified Copia-like retrotransposons within the C. sativa genome. These elements may play a pivotal role in dictating the expression of male or female phenotypes, shedding light on the underlying genetic mechanisms governing sex determination in cannabis.

ISSR Analysis: Exploring Genetic Diversity

The utilization of Inter Simple Sequence Repeat (ISSR) analysis demonstrated varying levels of polymorphism in both hermaphroditic and cross-fertilized populations. This highlights the genetic diversity within these populations, offering valuable insights into the adaptability and resilience of these cannabis varieties.

Nei’s Index of Gene Diversity and Shannon’s Information Index: Quantifying Diversity

Both indices, commonly used to measure genetic diversity within populations, yielded statistically similar results for both hermaphroditic and cross-fertilized populations. This suggests that, despite their different reproductive strategies, these populations possess comparable levels of genetic diversity.

Additionally, due to higher levels of hormones in male plants, the trichome composition theoretically contains more cannabinoids and trichomes, even though male plants produce significantly fewer of them than females. This phenomenon arises from the male's allocation of more energy towards growth hormones, as it requires less energy for males to produce pollen compared to the energy required for females to produce seeds. This contributes to the unique chemical profiles observed in male cannabis plants.

Additionally, here are the hormone levels for each type:

• Male Plants:

• Auxin: High
• Gibberellin: High
• Cytokinin: High

• Female Plants:

• Auxin: Medium
• Gibberellin: Low
• Cytokinin: Low

• Hermaphrodite Plants:

• Auxin: Medium
• Gibberellin: Medium
• Cytokinin: Medium

In conclusion, the study of dioecious male/female and monoecious hermaphrodite cannabis plants provides valuable insights into the intricate world of plant reproduction. Understanding the genetic, morphological, and hormonal intricacies of these varieties offers opportunities for further research and potential applications in cultivation practices and genetic engineering. The adaptability and unique characteristics of these cannabis varieties continue to be a subject of fascination and exploration within the scientific community.

 Frontiers | Hermaphroditism in Marijuana (Cannabis sativa L.) Inflorescences – Impact on Floral Morphology, Seed Formation, Progeny Sex Ratios, and Genetic Variation (frontiersin.org)