Question

Which one of the following is correct about pinus?
a. Monoecious - male and female sporophylls borne on the same strobili.
b. Monoecious - male and female sporophylls borne on seperate strobili.
c. Dioecious - male and female sporophylls on different strobili and on different plants.
d. All of the above.

Answer 1

In plants, the leaves on which the sporangia (spore forming tissues) are formed are known as sporophylls. In gymnosperms, these sporophylls are arranged spirally along an axis to form loose or compact strobili or cones. There are two types of cones known as the male and female cones or strobili.

Complete answer:
- When the male and female cones are produced on the same tree, the plant is known to be monoecious and when they are produced on different trees, the plant is known to be dioecious.
- With respect to sporophylls, when the male and female sporophylls are borne on seperate strobili, the plant is said to be Monoecious and otherwise, it is dioecious.
- Pinus is a monoecious gymnosperm, having both male and female cones on the same plant and the male and female strobilus are borne on seperate strobili.
- The male cone of the pinus contains microsporangia which further produces microspores (pollen grain).
- The female cone contains the megasporangium which produces the megaspores.
- Fusion of these spores results in the formation of zygote and then the embryo.
- The pollen grains of pinus are referred to as winged pollen. Thus pollination in the pinus occurs via wind and then these pollen reach the megaspores and fuse with them.

Hence, the correct answer is option (B).

Note: Pinus is included in the largest group of gymnosperms known as coniferales. Thus it is also known as a conifer. The body of the pinus is differentiated into true roots, stem and pointed needle like leaves. In pinus, the female cone or strobili is reduced as compared to the male cone or strobili. Hence the megaspores (large sporophylls) are referred to as the female cone in a pinus plant.