what is a possible advantage of releasing pollen before the leaves expand?

Answer 1

Plants have various mechanisms that prevent self-fertilization.

Some flowers self-fertilize or “self,” but most angiosperms have mechanisms that make this difficult or impossible.

The various barriers that prevent self-fertilization contribute to genetic variety by ensuring that sperm and eggs come from different parents.

Dioecious plants cannot self-fertilize because they are unisexual.

In plants with bisexual flowers, a variety of mechanisms may prevent self-fertilization.
For example, in some species stamens and carpels mature at different times.

Alternatively, they may be arranged in such a way that it is mechanically unlikely that an animal pollinator could transfer pollen from the anthers to the stigma of the same flower.

The most common anti-selfing mechanism is self-incompatibility, the ability of a plant to reject its own pollen and that of closely related individuals.

If a pollen grain from an anther happens to land on a stigma of a flower on the same plant, a biochemical block prevents the pollen from completing its development and fertilizing an egg.

The self-incompatibility systems in plant are analogous to the immune response of animals.

Both are based on the ability of organisms to distinguish “self” from “nonself.”

The key difference is that the animal immune system rejects nonself, but self-incompatibility in plants is a rejection of self.

Because the pollen grain is haploid, it will be recognized as “self” if its one S-allele matches either of the two S-alleles of the diploid stigma.

Although self-incompatibility genes are all referred to as S-loci, such genes have evolved independently in various plant families.

As a consequence, self-recognition blocks pollen tube growth by different molecular mechanisms.

In some cases, the block occurs in the pollen grain itself, called gametophytic self-incompatibility.

In some species, self-recognition leads to enzymatic destruction of RNA within the rudimentary pollen tube.

Eventually, it may be possible to impose self-incompatibility on species that are normally self-compatible.

expanding the leaves is also one of the type

hope this helps u to understrand the phenomenon

Answer 2

If the pollen is carried by the wind, then the leaves would not interfere with the pollen reaching the female flowers.