Abstract

Poikilohydry, or the lack of control of water relations, has typically been a subject studied by lichenologists and bryologists. For many years, much was unknown about poikilohydrous vascular plants, and evidence for their abilities was mostly anecdotal. A small number of these plants were studied by a few physiologists and ecologists who were fascinated by the capability of these ‘‘resurrection plants’’ to quickly switch from an anabiotic to a biotic state and vice versa (Pessin 1924, Heil 1925, Walter 1931, Oppenheimer and Halevy 1962, Kappen 1966, Vieweg and Ziegler 1969). Recently, a practical demand has released an unprecedented interest in poikilohydrous plants. The increasing importance of developing and improving technologies for preserving living material in the dry state for breeding and medical purposes has induced tremendous research activity aimed at uncovering the molecular and biochemical basis of desiccation tolerance. Poikilohydrous plants have proven to be very suitable for exploring the basis of this tolerance with the target of genetic engineering (Stewart 1989, Oliver and Bewley 1997, Yang et al. 2003, Bernacchia and Furini 2004, Alpert 2006). Consequently, much of the current literature discusses poikilohydrous plants mainly as a means of explaining basic mechanisms of desiccation tolerance (Hartung et al. 1998, Scott 2000, Bartels and Salamini 2001, Rascio and Rocca 2005) instead of exploring their origin, life history, and ecology (Raven 1999, Porembski and Barthlott 2000, Belnap and Lange 2001, Ibisch et al. 2001, Proctor and Tuba 2002, Heilmeier et al. 2005).