Question

a) Explain the likely steps in pollen from the male cone travelling to, and then fertilising, an egg in the female cone scale

b) What are the similarities and differences between the female cone scale and the male cone?

c) Explain the main morphological features of the female cone scale and the male cone?

Answer 1

Answer 1. The pollination in gymnosperms is through wind. Wind is the carrier of pollens. This is why gymnosperms produce huge amount of plooens to ensure fertilisation. The pollens are winged and are shed over the female cones and laid over the sticky area of scale. The scale opens up for the entry of pollens and the pollen stays there till ext spring season. Till then inside the female cone, slow divisions occur in which male and female gametes are being produced after meiosis. In favourable season, the pollen tube grows inside the ovule towards the micropyle where the egg is lying. There the fertilisation process occurs.

Answer 2. Differences:-Male cones are smaller in size than females. Male cones have pollens and tight scales. Female cones have loose scales and unfertilized eggs. Male cones are found above the tree and female cones are low lying.

Similarities :- Both male and female cones have scales. Both the cones have megasporangium to keep the spores or gametes. Both produce gametes with meiosis.

Answer 3. The structure of male cone is simple, oval, compact with size of about 2-3 cms. They occur in clusters and found on the top of trees. These cones have a short and elongated central axis which has a large number of microsporophylls or stamens on it, which are spirally arranged.

The female cones also have microsporophylls arranged spirally on the central axis stem. These cones have large ovuliferous scales and lower smaller bract scales on it. They are developed either single or in groups of 2 to 4. The female cone is ovoid in young age and becomes cylindrical at maturity.