Sex in plants

So, after wondering about evolution of words meanings and issues about gender and sex, I may post a very basic summary of how botanists happen to characterize sex in their study species. There’s indeed many levels, from flower to population, and sex (reproductive organs arrangement) and gender (relative investment into male and female functions) vary all along these lines. Yep, this is just a simplified view of sex classification in plants… Real world observations sometimes drive you into some more mitigated path.

So let’s see first about the most basic level in flowering plant reproductive structure, i.e. at the flower level:

Flower	Caracteristics
Pistillate	With functional pistil and fertile ovules	Female function only (sometimes called “male-sterile”)
Staminate	With stamen containing viable pollen grains	Male function only
Perfect	With both female and male functions	Hermaphroditic flower

Sometimes either stamen or pistils are present at a vestigial (and non-functional) stage.There are also various intermediate stages, notably for stamens, the full characterization of which is often a tedious task, for example when pollen number, or when pollen viability varies, etc.

Now, we can move on the distribution of these different flowers in the individual plant:

Individual	Caracteristics
Female	With pistillate flowers
Male	With staminate flowers
Monoecious	With both female and male flowers
Gynomonoecious	With both female and perfect flowers
Andromonoecious	With both male and perfect flowers
Hermaphrodite	With perfect flowers
Trioecious	With perfect, female and male flowers

There are numerous ways plant sex can depart from hermaphroditism, even if such a sex determination is not directly inherited as an ancestral state. Most surprisingly, any situation can be reached by both a slow graduation or an abrupt appearance, depending on the kind of mutation giving rise to those phenotypes.

Some mutations involving cytoplasmically inherited elements such as mitochondria are known to produce immediate male-sterility, for example. All of this can vary from one population to the other, and usually such a variation is the rule. Female sterility, on the other hand, is something somewhat rarer but does happen from time to time.

Please note that female function is also complex, because some flowers may produce typical female structures (from ovary to stigma) without actually being able to mature fruits and seeds, even when living in a rich environment.

OK. So now, we can safely take a look as to how those different plants are occuring at the population or the species level. Here is what happens in relatively simple situations:

Population/Species	Caracteristics	Example
Monoecious	With monoecious plants	Zea mays, the Corn
Dioecious	With both female and male plants	Cannabis sativa, the Hemp (usually students know about this one)
Gynomonoecious	With both female and hermaphrodite individuals	Fragaria virginiana (I really don’t see why it’s the first example that comes to my mind… ;)
Andromonoecious	With both male and hermaphrodite individuals	Solanum carolinense
Hermaphrodite	With hermaphroditic individuals	Fragaria vesca, the Common Strawberry, among so many others…
Trioecious	With perfect, female and male individuals	Fraxinus excelsior, the European Ash. Actually, it’s even more diverse and would also fit into the next two lines of the table, depending on population under drift influence.Anyway in this case we are confronted to a species that’s undecided yet, and this situation is sometimes called polygamous. This last term is nevertheless not a good choice because of the confusion with the common meaning of polygamous (which characterizes most flowering plants species by the way).
Gynomonoecious-gynodioecious	With female, gynomonoecious and hermaphroditic individuals
Andromonoecious-androdioecious	With male, andromonoecious and hermaphroditic individuals

I guess you now have a new game with your kids for the next walk through the meadow…