Question

Differentiate between geitonogamy and xenogamy in plants. Which one will lead to inbreeding depression and why?

Answer 1

Hint: Geitonogamy and xenogamy are both different routes of pollination adapted by plants.

Complete Answer:

Sl.No	GEITONOGAMY	XENOGAMY
1	Geitonogamy is the transfer of pollen from the anther of one flower to the stigma of another flower on the same plant.	Xenogamy is the transfer of pollen from the anther of one flower of a plant to the stigma of another flower of a different plant.
2	It functions as a cross-pollination method but genetically similar to autogamy.	It is a cross-pollination method.
3	The pollen grains have similar genetic build-up.	Pollens have different genetic build-up since they're from different plants.
4	The offsprings produced are genetically identical.	The offspring may have genetic variations.
5	Mostly maintains the parental characters.	Mostly undergoes variations and mutations.
6	Anemophilous flowers mainly perform geitonogamy.	Entomophilous flowers mainly perform xenogamy.
7	Eg: Monoecious gymnosperms like maize.	Eg: Squash, Broccoli, onion.

Inbreeding depression is a phase where the biological fitness of a species is reduced due to generation after generation of breeding between pure races. The ability of the population to perpetuate in an environment decreases due to inbreeding depression.
Geitonogamy brings about inbreeding depression because of its pollination between genetically identical flowers.
- Since the flowers are borne on the same plant, the pollination mimics autogamy genetically, although functionally it is cross-pollinated by pollinators like the wind.
- The same species of flowers involved in fertilization bring about no significant changes in the genetic makeup of the parent and the offspring.
- This goes on for generations and the surviving capacity of the plant in the constantly dynamic environment gradually decreases. This brings inbreeding depression to a large extent.

Note: Geitonogamy and inbreeding depression can be avoided by the naturally selected self-incompatibility of plants or by methods like emasculation and bagging.