New study sheds light on gender in gynodioecious plants

A team of researchers wanted to learn more about how and why gynodioecious plants change their sex, so they shone some light on the question. Literally.

Scientists from the University of Lincoln found that it’s the amount of light they receive that triggers sex changes in the relatively rare plants.

Gynodioecy in plants is a system of reproductive behavior in which plants can either be female or hermaphrodites. Female plants have all of their reproductive parts intact, but hermaphrodites do not produce pollen.

The new study shows that at least some plants express as female when light conditions are good. When conditions are poor, they become hermaphrodites.

Gynodioecious plants are comparatively rare. Most plant species are dioecious – they produce both male and female plants, and both participate in reproduction.

Scientists have known for some time that dioecious plants can switch gender from female to male and back due to environmental triggers. However, sex changes in gynodioecious plants have not been well studied before.

The researchers hoped to change that, so they conducted a study of 326 Geranium sylvaticum specimens.

“We conducted a transplantation experiment in the field where plants with different sex expression were reciprocally transplanted between high light and low light habitats. We measured plants’ reproductive output and sex expression over four years,” the scientists wrote.

They found that, regardless of each individual plant’s origin, those that received more light expressed their sex as female. Those that grew with less light were hermaphrodites.

“This study shows that sex expression in Geranium sylvaticum is [liable to change] and related to light availability,” the researchers wrote.

Because plants may live in light conditions that don’t change much from year to year, they might not change their sexes frequently. That means more species of gynodioecious plants may swap their genders than we thought, the scientists said – but no one has observed them yet.

The study was published in the journal American Journal of Botany.