This is an overview of research on sex expression in monoecious cannabis plants (plants that express male and female characteristics at the same time) and how sex expression is affected by different factors.
It is well known that majority of the cannabis plants are monoecious (express both male and female characteristics on the same plant) and dioecious plants are more rare (plants that express male and female characteristics on separate plants). Also predominantly male monoecious plants are known to be more sensitive to fungi. Hemp producres use feminised seeds to avoid plants with male characteristics.
Quantitative method is characterised by the percentage of male, female or hermaphrodite flowers or by the number or percentage of pastille nodes. In monoecious hemp, plants bear racemose inflorescences with male and female flowers arising in rations that vary among nodes along the stem and with time, in addition to being affected by environmental factors.
For the review the authors have used F1 population of 167 individuals that were derived from a cross between two monoecious plants, USO 31 and Fedora 17. Sex expression was based on the scale developed by Sengbusch (1952):
The researchers observed that the percentage of female nodes increase if the plant is feminised during flowering period. Also the percentage of male nodes decreases in the period between 43 and 78 days after sowing. The percentage of mixed male and female nodes is constant over time – average 25% of the nodes.
The nodes formation increases between day 43 and 64 after sowing and then remain constant. During that very same period is observed that maximum nodes are developed. Also feminised plants are more likely to express more female flowers than male ones.
The authors believe that their model confirm the assumption that expression of male and female flowers on the same plant is genetically determined and sex expression in response to environmental factors would not result in extreme male and female phenotypes.
This research shows that expression of male and female flowers on the same plant is genetically determined and such plants cannot be “forced” to express only male or female flowers using changes in environmental factors (for example, feminisation).
Modelling approach for the quantitative variation of sex expression in monoecious hemp (Cannabis sativa L.)