Measuring tolerance

Techniques for quantifying the degree of desiccation tolerance in different species are reviewed in Chapters 2-4 and 7. Chapter 2 discusses the advantages and limitations of different measures of water content and techniques for distinguishing water properties in plant cells. Chapter 3 notes how the survival and recovery rates of seeds and vegetative tissues vary with rate of drying, light conditions during drying, storage conditions and length of time in the dehydrated state. In general,...

Repair

The repair processes associated with desiccation tolerance have been difficult to detail and characterize. In seeds, repair mechanisms are difficult to separate from events that are associated with germination and early seedling growth, but evidence for repair does exist. In vegetative angiosperms, the major emphasis appears to be on effective cellular protection and much of the research in angiosperms has focused on this component. The most promising models for investigating a direct role for...

Habitats

In contrast to the wide taxonomic and geographical ranges and the broad morphological diversity of desiccation-tolerant vascular plants, their ecological range is narrowly confined to chronically or seasonally dry habitats or microhabitats where desiccation-sensitive plants are sparse or absent. Porembski and Barthlott (2000) estimated that 90 of desiccation-tolerant vascular plants are associated with rock outcrops, mainly in tropical to lower temperate latitudes. Some species grow on exposed...

The next step establishing records

The scientific battle over whether living things could dry without dying was fought over animals. Starting in the 1960s, tolerance was identified in the larvae of at least one insect and of some other arthropods (Hinton, 1968 Crowe et al., 1992) but has never been found in any life stage of any vertebrate or in the adults of any animals except microscopic rotifers, nematodes and tardigrades. In contrast, tolerance was found to be widespread in plants. Tolerant bryophytes were reported by 1886,...

The Ecology of Desiccation Tolerance in Plants a Diversity of Cycles in Marginal Habitats

Desiccation-tolerant plants grow mainly in the interstices and on the margins of the world's vegetation, in microhabitats and habitats where desiccation-sensitive plants do not live (Fig. 1.3). In habitats where water availability and temperature are moderate and sensitive plants are abundant, desiccation-tolerant vascular plants grow mostly on outcrops of bare rock (Porembski and Barthlott, 2000). In the driest and coldest habitats, especially where dew and fog are major water sources,...

Brief History of Research on Desiccation Tolerance

The 300-year history of the science of desiccation tolerance began with a lengthy period of discovery and doubt. In the course of discovering desiccation tolerance, scientists confronted the nature of life. The next step was to enumerate the organisms that tolerate desiccation and test the limits of their tolerance. In the 1960s, researchers started to investigate the physiological ecology of desiccation tolerance in plants, especially the cycles of wetting and drying and their effects on...

Seeds pollen and spores

As in adult plants, the desiccation tolerance of seeds can vary greatly between species within genera, between individuals within species and between tissues within individuals and there is a continuum of degree of tolerance across species Chapters 5 and 8 . However, whereas desiccation tolerance is rare in adult flowering plants, it is so much the rule in their seeds that tolerant seeds are traditionally known as 'orthodox' and desiccation-sensitive seeds as 'recalcitrant'. Desiccation...

Vegetative tissues

Barthlott Seed

Desiccation tolerance appears common though not universal in bryophytes e.g. Richardson, 1981 Proctor, 1990 , common in lichens Kappen and Valladares, 1999 , uncommon in pteridophytes and rare in angiosperms Chapter 7 . No gymnosperms are known to tolerate desiccation Gaff, 1980 Chapter 7 , even though gym-nosperms may have desiccation-tolerant seeds or pollen Chapters 5 and 6 . Desiccation tolerance occurs in non-lich-enized fungi, cyanobacteria and algae Ried, 1960 Mazur, 1968 Bertsch, 1970...