Evolutionary reproductive biologies in the Mesozoic plants of India

Abstract

The reproductive biologies in the Mesozoic plants are dealt with taking into consideration form and function of the reproductive organs. The Mesozoic flora inherited homospory, heterospory, pollen and seed formation from their Palaeozoic ancestors. Most of the Palaeozoic forms vanished by the close of Permian due to change of environment. The Triassic Period nursed the leftovers from the Permian as well as put forth new elements like Lepidopteris, Dicroidium and allied genera of Peltaspermaceae, Corystospermaceae and members of Caytoniaceae in which the seeds were protected in cupules. Thus the development of cupule in these genera changed the course of plant evolution. Later, with the amelioration of climate the cycads grew to prominence with exposed seeds, and subsequently they were overtaken by the rise of more advanced conifers. Meanwhile this flora also produced 'flower-like' structures in the cycadeoides and 'fruit-like' structures in Caytoniales and Pentoxyleae by providing fleshy growth around the seeds. The hot, arid conditions again reoccurred towards the close of the Early Cretaceous. At this time the angiosperms appeared with enclosed seeds, heralding another change in the course of plant evolution.