explain outbreeding devices? (contrivances)
Answers
Explanation:
Outbreeding devices are mechanisms which are followed and adapted by the plants in order to prevent self pollination. The examples of outbreeding devices are: ... Hetrostyly: The anther and stigma are present at different levels of the flower which prevents the self pollination and fertilization.
Explanation:
Continued inbreeding or self- fertilization leads to a condition called as inbreeding depression. This condition is characterized by homozygous genes which are not as vital as they need to be leading to unhealthy offsprings.
In self- pollination, since both the male and female gametes share the same genes, there is no genetic variation seen which is necessary for a better, more productive offspring. So, most plants have many mechanisms that they employ to avoid self -pollination and promote cross-pollination.
Outbreeding Devices
Plants have many mechanisms and devices that they employ to promote cross-pollination. Let us look at a few of them in the following segments:
Unisexuality: In this case, the plant bears either male or female flowers and is not hermaphrodite. It is also called as Dioecism.
Dichogamy: In this mechanism, the stigma and anther mature at different times. Depending on who matures first, dichogamy can be further divided into two:
Protandry: In this type, the androecium matures earlier than the gynoecium. Ex: maize plant
Protogyny: In this type, the gynoecium matures earlier than the androecium.
Herkogamy: This is a name given to a condition where there is a natural physical barrier that prevents the pollen of the same flower from entering the ovary.
Self- Sterility: In this condition, there is a gene that recognizes the similar gene and does not allow the pollen grain to germinate. This is due to the self-sterile gene present in the ovule and the grain
Heterostyly: In some plants like the oxalis, the stigma and the anthers are placed at different levels. This prevents the pollen from reaching the stigma and pollinating it.
Pollen prepotency: In this mechanism, the pollen of a different flower germinates faster than of the same flower thus preventing autogamy.
Pollen-Pistil interaction
Pollen