Self-incompatibility can be defined as a situation where the pollen from one flower is unable to fertilize the ovules of that same flower or any other flower on the same plant.
This mechanism is thought to help promote outcrossing and genetic variation in plants.
It is important to note that self-incompatibility does not always lead to infertility – in some cases, the pollen may still be able to germinate and produce a pollen tube, but the development of the embryo will be arrested at an early stage.
As a result, seed formation does not occur and the plant does not produce offspring.
Why does self-pollination not lead to seed formation in self-incompatible species?
There are several possible reasons why self-pollination does not lead to seed formation in self-incompatible species.
- One possibility is that the pollen tube may be unable to penetrate the stigma, or it may be arrested at an early stage of development
- Another possibility is that the embryo may be unable to develop properly if it is formed from self-pollinated ovules
- In self-incompatible plants, the presence of a matching allele or genotype on the stigma is often enough to trigger SI. This means that even if the pollen is from a different plant, it may not be able to fertilize the ovules if it carries the same allele.
So, self-pollination in self-incompatible species does not lead to seed formation because embryo development is arrested and there is no viable seed formed.
How do self-incompatible plants pollinate?
Plants with self-incompatibility (SI) cross-pollinate by transferring pollen from one plant to another. The pollen grains of SI plants are unable to germinate and grow on the stigma of the same plant or another plant with a matching allele or genotype.
What are the causes of self-incompatibility?
The causes of self-incompatibility are not fully understood, but it is believed to be the result of a combination of genetic and environmental factors. In plants, SI is often caused by alleles that produce proteins that recognize and bind to other alleles (self-antigens) on the surface of pollen grains or ovules. These proteins can inhibit pollen germination, pollen tube growth, ovule fertilization, or embryo development, leading to the production of no seeds. It is also possible for environmental factors, such as soil moisture or temperature, to influence the expression of self-incompatibility genes and prevent self-fertilization.
Why is self-incompatibility important in diversity?
Self-incompatibility is important in diversity because it promotes outcrossing and allogamy, which helps to introduce new genes into a population. This is important as it helps to prevent inbreeding and maintain genetic variation.