Scientists have discovered that plants can have more than two sexes

Most people rarely give much thought to exactly how plants reproduce. However, a new scientific explanation shows the "sex lives" of plants are much more diverse and complex than is commonly believed.

Biologist Lila Maladeski explained this in an article for The Conversation on the evolution of sexual systems in flowering plants.

Most plants are "bipedal," but not all of them are

According to scientists, about 90 per cent of flowering plants are hermaphrodites - their flowers simultaneously perform male and female functions. For example, in tomatoes, one and the same flower contains both pollen and ovary, which allows the plant to self-pollinate without the participation of neighbours.

However, even among such plants there are exceptions. Apple trees, for example, are incapable of self-pollination and need another plant to produce fruit.

Plants with a "separation of the sexes"

The remaining 10% or so of flowering plants have more complex reproduction systems. In some species, male and female flowers exist separately but on the same plant - such plants are called unisexual. Often these flowers open at different times, which prevents self-pollination.

There are also plants with completely separated sexes - dicotyledonous species, where individuals are either "male" or "female". An example is willows, where one tree produces only pollen and the other only seeds.

According to scientists, this separation helps to avoid the negative effects of self-pollination, which can lead to weakened offspring.

Intermediate and rare systems

Research shows that there are also rarer, "transitional" forms in nature:

• androdiesis - when hermaphroditesand males occur in a population;

• gynodience - the coexistence of hermaphrodites and females;

• triecy - the presence of three types of individuals at once: males, females and hermaphrodites (example: papaya).

These systems are rare, but are important in understanding the evolution of reproduction.

The evolution of sex is a reversible process

Scientists believe that the first flowering plants were hermaphrodites, and that all other systems emerged later and independently. Genetic studies show that the separation of the sexes in plants appeared many times and in different groups.

Moreover, evolution does not always go in one direction: plants can go from hermaphroditism to sexual separation and back again, depending on environmental conditions and biological challenges.

Why this is important for science

The diversity of sexual systems in plants makes them a unique model for studying evolution. Unlike animals, where the separation of the sexes is often fixed for millions of years, plants show flexibility and constant change.

According to researchers, there is no "perfect" sexual system - its efficiency always depends on the environment, climate and survival strategy of a particular species.