Submitted to: Botanical Society of America Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2001
Publication Date: N/A
Technical Abstract: Vegetative desiccation tolerance is a widespread but uncommon occurrence in plants. The majority of desiccation-tolerant plants are found in the less complex clades that constitute the algae & bryophytes. However, within the larger & more complex groups of vascular land plants there are some 120-130 species that exhibit some degree of vegetative desiccation tolerance. A phylogenetic look at vegetative desiccation tolerance reveals that this capability was lost during the time when tracheophytes first evolved & subsequently re evolved at least 12 separate times in various vascular plant lineages. The primitive mechanism of vegetative desiccation tolerance in the first land plants probably involved constitutive cellular protection coupled with active & inducible cellular repair, similar to that described for modern-day desiccation-tolerant mosses. Desiccation-tolerant angiosperms utilize an inducible cellular protection mechanism of tolerance ethat appears to derive from the programmed cellular protection mechanism seen in seeds. Desiccation-tolerant pteridophytes appear to employ a mechanism of tolerance that has characteristics of both the primitive & the more recently evolved mechanisms. Much of our evidence comes from the interpretation of a wealth of physiological data derived from the ecophysiology of Selaginella lepidophylla & a few desiccation tolerant ferns such as Polypodium polypodioides. However, detailed mechanistic studies have only been attempted using the desiccation-tolerant fern Polypodium virginianum. Pteridophytes are in a unique position for the study of desiccation tolerance & its role in the evolution of the land plants & that with the availability of the modern tools of genomics the time is right for this area to expand.