Read the passage and answer the following questions:
A typical microsporangium, when observed in a transverse section, has a nearly circular shape. It is typically surrounded by four layers of walls: the epidermis, endothecium, middle layers, and the tapetum. The outer three wall layers serve to protect the microsporangium and aid in the anther's opening to release the pollen. The innermost wall layer, known as the tapetum, provides nourishment to the developing pollen grains. Tapetum cells are characterized by their dense cytoplasm and often contain multiple nuclei. In angiosperms, an anther usually consists of two lobes, each with two theca, making it dithecous. The theca are often separated by a longitudinal groove. The anther itself has a tetragonal shape with four microsporangia situated at its corners, two in each lobe. These microsporangia undergo further development and transform into pollen sacs.
Given below are two statements:
Statement I: The distal end of the filament of a stamen is attached to the thalamus or the petal of the flower.
Statement II: The number and length of stamens are variable in flowers of different species.
In the light of the above statements, choose the correct 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
A stamen has two parts: the long, slender stalk called the filament and the terminal anther. The anther sits at the free (distal) end of the filament, while the other end, the proximal end, is fixed to the flower.
Statement I: The distal end of the filament of a stamen is attached to the thalamus or the petal of the flower. — False. It is the proximal end of the filament that is attached to the thalamus or the petal. The distal end bears the anther.
Statement II: The number and length of stamens are variable in flowers of different species. — True. Stamens collected from flowers of different species show a large variation in size, shape and attachment of anthers.
So Statement I is incorrect and Statement II is correct.
NCERT Extract:
Stamen, Microsporangium and Pollen Grain – “Figure 1.2a shows the two parts of a typical stamen – the long and slender stalk called the filament, and the terminal generally bilobed structure called the anther. The proximal end of the filament is attached to the thalamus or the petal of the flower. The number and length of stamens are variable in flowers of different species.”
Figure 1.2 (a) A typical stamen; (b) three-dimensional cut section of an anther