Question

Which of the following is an outbreeding device?

a. If pollen release and stigma receptivity are not synchronized.

b. If the anther and stigma are placed at different positions so that pollen cannot come in contact with the stigma of the same flower.

c. Self-incompatibility which prevents self-pollen (from the same plant) from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in the pistil.

d. Production of the unisexual flower.

• A. $a,b$ and $c$
• B. $b,c$ and $d$
• C. $a,c$ and $d$
• D. $a,b,c$ and $d$

Answer 1

The correct option is D $a,b,c$ and $d$

Majority of flowering plants produce hermaphrodite flowers, so pollen grains are likely to come in contact with the stigma of the same flower. Continuous self-pollination result in inbreeding depression. Flowering plants have developed many devices to discourage self-pollination and to encourage cross-pollination.
Outbreeding devices are:

• In some species, pollen release and stigma receptivity are not synchronised. Either the pollen is released before the stigma becomes receptive or stigma becomes receptive much before the release of pollen. This condition is called dichogamy in which stigma and anther matures at different time.
• In some species, the anther and stigma are placed at different positions so that the pollen cannot come in contact with the stigma of the same flower. This condition is called heterostyle.
• Self-incompatibility which prevents self-pollen (from the same plant) from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in the pistil.
• Production of the unisexual flower.