Gymnosperm Reproduction & Naked Seeds — NEET Biology

The gymnosperms are the plants in which ovules are not enclosed by any ovary wall. After fertilisation the seeds remain exposed and therefore these plants are called naked seeded plants. The gymnosperms produce microspores and megaspores which are produced in microsporangia and megasporangia borne on the sporophylls. The sporophylls - microsporophylls and megasporophylls – are arranged spirally on axis to form lax or compact cones or strobili. The pollen grains and ovules develop on different sporophylls and hence the plants are heterosporous. Reduction division in the microspore mother cell and the megaspore mother cell results in the formation of microspores and megaspores. The endosperm is formed before fertilisation and is therefore called prothallus. The microspores develop into a male gametophytic structure called pollen grain. The pollen grains are released from the microsporangia and carried by wind to fall on the ovules borne on megasporophylls. The wall of the microspore extends to form a pollen tube. The pollen tube carries the male gametes to the archegonia where the male gamete fuses with the egg cell of the female archegonium. Following fertilisation, the zygote develops into embryo and the ovules into seeds.