Sexual Reproduction in Flowering Plants Test - 11

Tapetum is the cells surrounding the microspore mother cells. These cells provide nourishment to young microspore mother cell.

Self-pollination continuously leads to establishment of pure line. All genetic traits become similar in different offspring. Plants try to avoid self –pollination by using outbreeding devices.

Some flowers do not open at all. Self-pollination is the only means of pollination in these flowers. These flowers are called Cleistogamous flower. The other flowers that open for pollination are called Chasmogomous flower.

Large amount of fossilized pollen grain are found during excavation process of older parts due to tough covering of Sporopollenin that make the outer wall of pollen grain, exine. This substance cannot be hydrolyzed by any enzyme known

Self-pollination involves transfer of pollen grain from anther to stigma of same flower. The two fusing gametes are genetically similar to each other as they are produced by same plant. Continued self –pollination results into pure line and breeding depression.

Inbreeding occurs in intraspecific flowers as contain same kinds of genetic materials. Outbreeding takes place between interspecific flowers having different kinds of genetic materials.

Each microspore mother produces 4 pollen grains by reduction division. Bilobed dithecious have four microsporangium. Therefore, 50x4x4=800 male gametes are formed.

Pollen grain consists of hard covering of exine but their viability may lost with time. For Hybridisation pollen grains are collected and stored in liquid nitrogen below -196 degree Celsius temperature.

Microspores are male gametes. Formation of microspore takes place inside microsporangium which contains Sporogenous tissue. Sporogenous tissue undergoes reduction division to form tetrad that separate from each other and becomes microspore.

Pollination by winds is more common among the abiotic pollinations. Wind pollination requires that the pollen grains are light and non-sticky so that they can be transported in wind currents.