In plants, continued self-pollination results in

Question

Prepp Team · Accepted Answer

Understanding Self-Pollination in Plants

Self-pollination is a type of pollination in which pollen from the anthers of a flower is transferred to the stigma of the same flower, or to another flower on the same plant.

While self-pollination ensures seed production even when pollinators are scarce, continuous self-pollination over many generations can lead to certain consequences in plants.

Impact of Continued Self-Pollination

When a plant undergoes self-pollination repeatedly, it leads to increased homozygosity in the population. This means that recessive alleles, which might be deleterious (harmful) in homozygous condition, become expressed. Normally, in a diverse population with cross-pollination, these recessive alleles are often masked by dominant alleles in heterozygous individuals.

The accumulation and expression of these harmful recessive alleles due to continued self-pollination result in a phenomenon known as inbreeding depression.

What is Inbreeding Depression?

Inbreeding depression is the reduced biological fitness in a given population as a result of inbreeding. Fitness can refer to various aspects like:

Reduced vigour
Decreased yield
Lowered fertility
Reduced disease resistance
Increased susceptibility to environmental stress

Essentially, the plant population becomes weaker and less healthy over successive generations of self-pollination.

Analyzing the Options

Let's look at the provided options:

Outcrossing: Outcrossing is the opposite of self-pollination. It is pollination between genetically distinct individuals. Continued self-pollination does not result in outcrossing; rather, outcrossing is a mechanism that can help counteract the effects of continued self-pollination.
Inbreeding depression: As explained above, continued self-pollination increases homozygosity, leading to the expression of deleterious recessive alleles and a reduction in fitness, which is precisely inbreeding depression.
Self-incompatibility: Self-incompatibility is a genetic mechanism in many plants that prevents self-pollination or fertilization by pollen from the same plant. It is a mechanism to promote cross-pollination, not a result of continued self-pollination. Plants that exhibit self-incompatibility would naturally avoid continued self-pollination.
Male sterility: Male sterility is a condition in plants where the male reproductive organs (anthers or pollen) are non-functional. While male sterility prevents self-pollination (if the plant is also female fertile), it is a trait itself, not a direct consequence that *results* from continued self-pollination in a population over generations. It can be used by breeders to facilitate cross-pollination.

Based on the analysis, the direct result of continued self-pollination in plants is inbreeding depression.

Comparison of Terms
Term	Description	Relationship to Self-pollination
Self-pollination	Pollen transfer within the same flower or plant.	The process itself.
Outcrossing	Pollination between different plants.	Opposite of self-pollination.
Inbreeding depression	Reduced fitness due to increased homozygosity from inbreeding (like continued self-pollination).	A direct result of continued self-pollination.
Self-incompatibility	Genetic mechanism preventing self-pollination.	A mechanism to avoid self-pollination.
Male sterility	Non-functional male reproductive parts.	A condition that can prevent self-pollination, not a result of it.

Therefore, continued self-pollination results in inbreeding depression.

Revision Table: Continued Self-Pollination Effects

Key Concept	Explanation	Outcome of Continued Self-Pollination
Self-pollination	Transfer of pollen within the same plant.	Basis for the effect.
Homozygosity	Having two identical alleles for a trait.	Increases significantly.
Deleterious recessive alleles	Harmful genes masked in heterozygotes.	Become expressed more often.
Inbreeding depression	Reduction in vigor, yield, fertility, etc.	Direct and major result.

Additional Information: Managing Inbreeding Depression

To avoid or reverse inbreeding depression, plant breeders often practice outcrossing or cross-pollination. Introducing genetic variation from unrelated individuals can restore heterozygosity and mask the deleterious recessive alleles, leading to increased hybrid vigour (heterosis). This is why hybrid seeds often show better performance than seeds from self-pollinated lines.

Many naturally cross-pollinating plants have mechanisms like self-incompatibility, different timing of male and female flower parts (dichogamy), or unisexual flowers to prevent self-pollination and maintain genetic diversity, thus avoiding inbreeding depression.