The sex in many of the flowering plants is unstable and changeable

Writing / Irene Vega

The main result of this study, published in the scientific journal Philosophical Transactions of the Royal Society, reveals that almost all flowering plants for which sex chromosomes are known -a total of 22 species- show some indication of inconstancy in their sexual expression.

The scientific team found three ways in which those plants with sex chromosomes moved away from displaying two sexes, male and female. First, eight species changed sex between breeding events or within the same event, such as marijuana, hops, and asparagus. Second, in fifteen of them, one or both sexes produced some flowers of the opposite sex. And, finally, eleven species showed bisexual individuals, in addition to males and females, that is, three sexes were observed. “Twelve of the twenty-two species showed these three modes of departure from sexual expression with two sexes expected if the sex chromosomes were fully sex-fixed. Only four species did not show evidence of this 'sexual lability', but they are closely related to others that are labile”, explains Marcos Méndez Iglesias, a researcher in the Evolutionary Ecology group of the URJC Biodiversity and Conservation area.

These results underscore how little is known about the function of the sex chromosomes, based primarily on studies of some animals. “Flowering plant research allows us to broaden that understanding,” underlines the researcher, who adds that “most flowering plants are hermaphroditic and contain both sexes in the same flower. Only 6% of flowering plants have evolved the separation of the sexes and there are male and female individuals, as occurs in most animals”. Therefore, unlike what happens in animals, this evolution has been relatively recent. This makes flowering plants a very suitable system for studying how sex chromosomes evolve because, as Marcos Méndez points out, “all the steps from 'young chromosomes' that are poorly differentiated to more advanced sex chromosomes are found in them. That is, flowering plants make it possible to capture the evolution of sex chromosomes in action.”