Cycas revoluta
Classification:
Kingdom: Plantae
Division: Sporophyta (seed plant)
Class: Cycopsida
Order: Cycadales
Family: Cycadaceae
Genus: Cycas
Species: revoluta
Occurence: Cycas are perennial evergreen trees. They appear like a palm tree. They are characterised by the presence of naked seeds (ovules are not enclosed within the ovary). The main body part is a diploid sporophyte.
Cycas has about twenty species & is largely restricted to South East Asia, though some species occur in China, Japan, Australia & some Pacific Islands.
Structure: Cycas is a slow-growing, palm-tree like plant of 3-5 metres in height. It is a sporophyte & is differentiated into roots, stem & leaves. The plant is anchored by a think, short-lived tap root which is soon replaced by a number of adventitious roots.
The stem is short, stout, unbranched & erect with a crown of leaves at the top. The stem is covered by persistent bases of leaves.
Leaves are of two types - small, brown, scale leaves & large-sized green foliage leaves. Leaves are unipinnate compound & arranged in an alternate rings. Each leaf bears narrow, elongated, sharply pointed leaflets on the two sides of the rachis.
Cycas are gymnosperms, some of which have tall unbranched trunks with an armourlike appearance; others have partially buried stems with swollen or tuberous trunks. The stem has a large pith surrounded by a narrow zone of soft woody tissue. Male cones produce pollens, which are carried by wind to the female cones which are borne on separate plants where fertilization will occur.
Reproduction: Cycas shows vegetative as well as sexual reproduction. Vegetative reproduction will occur through the formation of bulbils or adventitious buds. Reproduction occurs sexually through formation of seeds.
In vegetative reproduction, adventitious buds or bulbils will develop in the axils of scaly leaves. They will then detach from the stem and develop into new plants. The bud from the male plant will develop into a male plant and the bud from the female plant will then develop into a female plant.
In sexual reproduction, Cycas being heterosporous will produce two kinds of spores. It is dioecious therefore the male and female reproductive parts are borne on different plants. The sexual reproduction is oogamous wherein the egg is quite large in size and non-motile compared to the male gamete.
Economic importance: Many spcies of Cycas are used as ornamental plants. However, some part of this species of plants are used to prepare alcoholic drinks. Its leaves are used for decoration & to prepare baskets, hats, etc. Parts of these plants can cure ulcers, sores, swellings & are used to treat vomiting & flatuleance as well.