Question

In obdiplostemonous androecium, stamens are arranged in
(a) One whorl alternating with petals
(b) Two whorls with outer whorl opposite the petals
(c) Two whorls with outer whorl alternating the petals
(d) One whorl opposite the petals

Answer 1

Hint: An androecium of the stamen is the male reproductive organ of a flower. It consists of an anther and a stalk. The obdiplostemonous androecium is the arrangement of stamens which is popularly seen in Dianthus.

Complete step by step answer:
Different types of arrangement of stamens can be observed in a flower. Stamens may be alternipetalous which means they alternate with petals with an anti petal arrangement which means the stamens are arranged opposite to the petals. In obdiplostemonous androecium, stamens are present in two whorls with outer epipetalous stamens and an inner alterna petaloid stamen. Thus, the stamens in the outer whorl of an obdiplostemonous androecium lie opposite to the petals. E.g Dianthus or Pink.

- The anther is bilobed with two pollen sacs known as microsporangia. In the wall of a mature anther, the epidermis is the outermost layer, followed by a single layer of endothelium, then one to the three- layered thick middle layer, and innermost single- layered tapetum.
- A strand of connective tissue extends from the filament to the anther. It is present between the two lobes and thus maintains their connectivity.
- The two pollen sacs in each lobe contain pollen grains.
- Stomium is a layer of thin- walled epidermal cells that are present at the line of dehiscence. Thus, when the time comes for the dispersal of pollen grains, anther breaks and splits at this line of dehiscence only.
So, the correct answer is ‘(b) Two whorls with outer whorls opposite the petals.’

Note:
- Tapetum consists of cells with large nuclei and dense cytoplasm.
- The main function of tapetum is the production and transport of enzymes, hormones, and nutrients, necessary for pollen development.
- Tapetum secretes callase, an enzyme to separate microspores or pollens from a microspore tetrad.