Read the passage and answer the following questions:
A typical angiosperm anther is bilobed with each lobe having two theca, i.e., they are dithecous. The anther is a four-sided (tetragonal) structure consisting of four microsporangia located at the corners, two in each lobe. The microsporangia develop further and become pollen sacs. They extend longitudinally all through the length of an anther and are packed with pollen grains. In a transverse section, a typical microsporangium appears near circular in outline. It is generally surrounded by four wall layers. When the anther is young, a group of compactly arranged homogenous cells called the sporogenous tissue occupies the centre of each microsporangium. As the anther develops, the cells of the sporogenous tissue undergo meiotic divisions to form microspore tetrads. As the anthers mature and dehydrate, the microspores dissociate from each other and develop into pollen grains. Inside each microsporangium several thousands of microspores or pollen grains are formed that are released with the dehiscence of anther.
Given below are two statements:
Statement I: In some cereals such as rice and wheat, pollen grains retain their viability for months after their release.
Statement II: Pollen grains stored in liquid nitrogen can be used as pollen banks, similar to seed banks, in crop breeding programmes.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Statement I is incorrect but Statement II is correct.
Once shed, a pollen grain stays viable only for a limited time. This period varies a lot from plant to plant and depends partly on temperature and humidity.
Statement I: In some cereals such as rice and wheat, pollen grains retain their viability for months after their release. — False. In rice and wheat, pollen grains lose viability within 30 minutes of their release. Viability for months is seen in some members of Rosaceae, Leguminoseae and Solanaceae.
Statement II: Pollen grains stored in liquid nitrogen can be used as pollen banks, similar to seed banks, in crop breeding programmes. — True. Pollen of many species can be stored for years in liquid nitrogen (−196°C), and such stored pollen is used as pollen banks.
NCERT Extract:
Pollen grain – “… The period for which pollen grains remain viable is highly variable and to some extent depends on the prevailing temperature and humidity. In some cereals such as rice and wheat, pollen grains lose viability within 30 minutes of their release, and in some members of Rosaceae, Leguminoseae and Solanaceae, they maintain viability for months. … It is possible to store pollen grains of a large number of species for years in liquid nitrogen (−196°C). Such stored pollen can be used as pollen banks, similar to seed banks, in crop breeding programmes.”