The Physiological Prerequisites for the Transition of Autotrophic Plants from Water to Terrestrial Life

Life originated in water and all living organisms depend on availability of water because only highly hydrated protoplasm can exhibit life activities. However, higher plants must tolerate conditions existing where their seeds fall and germinate, and where seedlings become established. A speculative discussion of evolutionary adaptations of plants to land, including the concepts of poikilohydric and homoiohydric plants, hydrature, and hydration, is followed by a discussion of adaptations of plant groups to water stress conditions.