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.
A student dusts some pollen grains of pea on a glass slide containing a drop of sugar solution (about 10 per cent). After about 15-30 minutes, the slide is observed under the low power lens of a microscope. What is the student likely to see?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Pollen tubes coming out of the pollen grains
Pollen grains of pea germinate in a drop of sugar solution (about 10 per cent). A germinating pollen grain sends out a pollen tube through one of its germ pores, and the tubes can be seen under the low power lens of a microscope after 15–30 minutes.
Option (1) Pollen tubes coming out of the pollen grains — Correct. This is pollen germination, the result of the activity.
Option (2) Male gametes released out of the pollen grains on the slide — Incorrect. Male gametes are not set free on a slide. They are carried inside the pollen tube and released in a synergid of the embryo sac.
Option (3) Microspores of a tetrad separating from one another — Incorrect. Microspores separate inside the anther as it matures and dries, before the pollen is shed.
Option (4) Exine of the pollen grains dissolving to expose the intine — Incorrect. The exine is made of sporopollenin, which withstands strong acids and alkali, and no enzyme that degrades it is known. A sugar solution cannot dissolve it.
NCERT Extract:
Pollen-pistil Interaction – “… You can easily study pollen germination by dusting some pollen from flowers such as pea, chickpea, Crotalaria, balsam and Vinca on a glass slide containing a drop of sugar solution (about 10 per cent). After about 15–30 minutes, observe the slide under the low power lens of the microscope. You are likely to see pollen tubes coming out of the pollen grains.”