Evolution, Diversity, and Habitats of Poikilohydrous Vascular Plants

Abstract

Only a few species of vascular plants are able to cope with extreme temporal variations of water availability. Most higher plants are homoiohydrous, i.e., their water content varies very little. Very exceptionally the water content of vascular plants follows fluctuations of humidity in their environment. Walter (1931) called plants whose water content closely follows fluctuations of humidity in their environment poikilohydrous. Desiccation tolerant vascular plants are able to survive cycles of dehydration and rehydration without losing viability. In the desiccated state they survive the loss of up to 95% of their cellular water. Detailed overviews of the ecological and physiological adaptations of resurrection plants were provided by Gaff (1981Gaff ( , 1989, Bewley (1995), Hartung et al. (1998), Tuba et al. (1998, Kluge and Brulfert (2000), Walters et al. (2002) and Kappen and Valladares (2007). A survey of the anatomy of desiccation tolerant vascular plants was given by Fahn and Cutler (1992). Recently, the molecular genetics of desiccation tolerance became objects of research (for surveys see Ingram and Bartels 1996; Phillips et al. 2002, see also Chaps. 13-17).Desiccation tolerance is widespread among cryptogams but is very rare among higher plants. Early reports of desiccation tolerant angiosperms were provided by e.g., Dinter (1918) and Heil (1924). Knowledge about their natural growth sites became more detailed through the studies of e.g., Hambler (1961) and Gaff (1977) which already emphasized the role of rock outcrops as habitats for desiccation tolerant vascular plants. Since almost two decades own studies are devoted to plant ecological investigations on granitic and gneissic outcrops (inselbergs) and ferricretes over a broad geographic spectrum. Inselbergs are characterized by harsh microclimatic and edaphic conditions, and desiccation-tolerant vascular plants dominate in certain plant communities (e.g., monocotyledonous mats). Based on extensive fieldwork and laboratory experiments, the existing knowledge on the systematic position and the ecology of desiccation tolerant vascular plants was summarized by Porembski and Barthlott (2000). It was demonstrated clearly that rock outcrops such as inselbergs form centres of diversity for poikilohydrous vascular plants. Rather neglected hitherto was the fact that the canopy of forests U. L€ uttge et al. (eds.), Plant Desiccation Tolerance, Ecological Studies 215,

Molecular mechanisms of desiccation tolerance in the resurrection glacial relic Haberlea rhodopensis

“…The mechanism of desiccation tolerance is common in bryophytes and lichens, less common in pteridophytes, rare in angiosperms, and absent from gymnosperms [5,6]. The complex plant tissues require mechanisms that prevent desiccation-induced cell and tissue damage in the first place; notably, the recovery from desiccation can be fast [7,8].…”

“…The complex plant tissues require mechanisms that prevent desiccation-induced cell and tissue damage in the first place; notably, the recovery from desiccation can be fast [7,8]. The small group of angiosperm resurrection plants (about 300 species) displays remarkable habitat and geographic diversity [5]. They are found in dry and desert areas, in more temperate areas with sufficient rain but short periods of drought or/and cold winters, and even in the tropical rainforests of Africa, where humidity is normally high [5,9,10].…”

“…The small group of angiosperm resurrection plants (about 300 species) displays remarkable habitat and geographic diversity [5]. They are found in dry and desert areas, in more temperate areas with sufficient rain but short periods of drought or/and cold winters, and even in the tropical rainforests of Africa, where humidity is normally high [5,9,10]. Most of the resurrection species are herbaceous plants, but there are also shrubs and trees [4].…”

Orthodox Seeds and Resurrection Plants: Two of a Kind?

“…Later, during the evolution of angiosperms, resurrection plants reacquired DT in their vegetative tissues through myriad genetic changes in at least 13 separate lineages (Oliver et al, 2005;Porembski, 2011;Gaff and Oliver, 2013). These lineages correspond to the angiosperm families containing resurrection species (Oliver et al, 2005;Gaff and Oliver, 2013).…”

“…1), such as Xerophyta humilis and X. viscosa, gradually dismantle their photosynthetic machinery, leading to almost Chlfree dehydrated leaves ( Fig. 2; Porembski, 2011;Tuba and Lichtenthaler, 2011;Beckett et al, 2012;Christ et al, 2014). In both X. humilis and X. viscosa, Chl degradation begins once leaf water content decreases below 80% RWC and continues to depletion in the air-dry state.…”