ABSTRACT
This chapter discusses structural and physiological features of poikilohydrous autotrophs and the different strategies in different ecological situations. It presents examples of poikilohydrous autotrophs living under very limiting ecological conditions in many different regions of the Earth. Nonvascular autotrophs are considered constitutively poikilohydrous because they lack the means of controlling water relations. In Africa, subfruticose poikilohydrous plants such as Lindernia crassifolia and Lindernia acicularis grow in sheltered rock niches. Poikilohydrous autotrophs, therefore, have had to trade-off between surviving desiccation against uptake, transport, and storage of water. Poikilohydrous plants that possess an internal system for water transport are exposed to cavitation during desiccation, which compromise the functioning of the conducting tissues upon rehydration. Poikilohydrous autotrophs can maintain their water content at a constant level only to a limited extent, but they can extend hydration into the dry period by certain, mostly structural, mechanisms.
