Poikilohydric Plants

Abstract

Poikilohydric plants differ from homoiohydric plants in that they can equilibrate with the relative humidity of the air during drought periods, but then exhibit complete physiological recovery upon rehydration (Bewley 1979; Evenari 1985b). The poikilohydric habit is found in both the cryptogamic autotrophs such as algae, lichens, mosses, and ferns, and a few vascular plant taxa such as the pteridophytes and lycophytes. Nonvascular cryptogams, particularly the lichens and mosses, form a majority of the species and biomass exhibiting poikilohydry within desert regions of the world, including North America. Some poikilohydric vascular plants have been termed “resurrection plants” (Gaff and Latz 1978). Several angiosperms exhibit poikilohydry (Gaff 1977, 1987; Gaff and Latz 1978); these are primarily grasses from semiarid regions with a distinct dry season. However, no higher vascular plants in North American deserts have yet been documented to exhibit poikilohydry.