Cycads: An overview

Abstract

Cycads are regarded as the “Living Fossils” and belong to a specialized group of plants having ancient lineage possessing great signifi cance from the evolutionary point of view. During excavations, the cycad fossils located and accepted as related to the similar lineage as the present-day cycads have been known from the early Permian period, ca. 280–320 Myr ago. They had been popularly known as “Plant Dinosaur” and were generally known as the most dominant plant group in the Mesozoic period. The relict group of the seed plants was worldwide in their distribution and dominant in the plant world as the dinosaurs were then at the peak in the animal world. They were eaten by some herbivorous dinosaurs, such as Stegosaurs. During that period the plant group Bennettitales or cycadeoids was in abundance which had superfi cial resemblance with cycads but was more similar and closer to the angiosperms. The Jurassic period is generally called as the “Age of Cycads” because they were very common at that time. In fact the cycads represent the basal living lineage of the presentday seed-bearing angiosperms. The taxonomic isolation and extreme antiquity of cycads have attributed them intrinsic interest and conservational importance which is disproportionate to the paucity of members because of their limited and disjunct distribution. The cycads are dioecious and very slow- growing plants; as a result they are getting extremely rare in the natural habitat. Due to their rarity, very attractive foliage and beautiful cones, cycads are considered as the prized collections in private and the public gardens leading to over exploitation from natural habitats and illegal trade in the international market. Therefore, international trade and the movement of cycads are regulated strictly under the rules governed by CITES. Botanic gardens have been recognized as prime custodians to play a vital role in maintaining the germplasm collection for the furtherance of taxonomic and ex-situ conservation studies on the cycads. This paper stresses upon taxonomic and conservational signifi cance of cycads and various reasons for the loss of cycad habitats world over including other important issues and parameters advocating for large-scale multiplication and ex-situ conservation programs in botanic gardens.