Question

Make a list of any three outbreeding devices that flowering plants have developed and explain how they help to encourage cross-pollination?

Answer 1

Hint: Continuous self-pollination leads to inbreeding depression and outbreeding leads to cross-pollination; plants have certain mechanisms by which they appear to prevent self-pollination.

Complete answer:
Plants have many tools that they use, called outbreeding devices, to facilitate cross-pollination. Outbreeding devices for cross-pollination in angiosperm plants are:
Stigma and pollen grain release receptivity is not coordinated, i.e., stigma becomes receptive long before pollen is released or released to avoid self-pollination.
Self-incompatibility: A genetic technique to prevent pollen from fertilizing ovules of the same flower by inhibiting stigma or pistil germination.
Manufacturing of unisexual flowers in such a way that male and female parts are found in the same plant on different plants, i.e., dioecious or different flowers (monoecious). It forbids both autogamy and geitonogamy.
Dicliny: The flowers are unisexual and cannot be self-pollinated. Plants can be single, meaning both male and female flowers (e.g., maize) or dioecious flowers with male and female flowers on separate plants (e.g., mulberry and papaya).
At separate stages, male and female reproductive components mature, preventing self-pollination. Dichogamy can be further divided into two types according to who matures first:
Protandry: Androecium matures in this form before gynoecium. Maize plants are just such an example.
Protogyny: Gynoecium matures earlier than Androecium in this form.

Note: Continuous inbreeding or self-fertilization occurs under a condition known as inbreeding depression. These diseases are characterized by homozygous genes that are not as important as those which lead to unhealthful offspring. In self-pollination, since both male and female flowers have the same genes, no genetic variation is required for a better and more productive birth. As a result, most plants have a number of mechanisms to discourage self-pollination and promote cross-pollination. Plant control and modification mechanisms to eliminate self-pollination are outbreeding devices.