Stress desiccation

Morison MO, Sheath RG (1985) Responses to desiccation stress by Klebsormidium rivulare (Ulotricales, Oilorophyta) from a Rhode Island stream. Phycologia 24 129-145... 

In certain plant habitats or niches, access to resources depends crucially upon rapid growth under conditions of climatic stress. Examples of this phenomenon are particularly obvious on shallow soils in continental climates where the growth window between winter cold and summer desiccation may be extremely short. In deciduous woodlands in the cool temperate zone an essentially similar niche arises in the period between snow melt and closure of the tree canopy. Both circumstances provide opportunities for high rates of photosynthesis and mineral nutrient capture in the late spring but depend upon rapid expansion of roots and shoots in the low-temperature conditions of the late winter and early spring. 

Polyols are present in desiccation tolerant lichens and liverworts, although not in mosses (Lewis, 1984). More generally starch hydrolysis and sugar accumulation occur in many plants experiencing severe water deficits (Hsiao, 1973). It is tempting to speculate that the accumulation of low molecular weight solutes in reponse to water stress represents a mechanism for the protection of membranes and proteins in the dry state. 

Fig. 1. A general, simplified and self-explanatory layout of the wheat breeding programme at the Volcani Center, Israel. The selection for drought resistance is affected at about the F4 and later generations, by using infra-red thermometry, chemical desiccation and yield under stress. A summer (off-season) nursery is incorporated as means for selection for heat tolerance.

Blum, A., Mayer, J. Golan, G. (1983a). Chemical desiccation of wheat plants asa simulator of post-anthesis stress. II. Relations to drought stress. Field Crops Research, 6, 149-55. 

Zilberstein, M., Blum, A. Eyal, Z. (1985). Chemical desiccation as a simulator of postanthesis speckled leaf blotch stress. Phytopathology, 75, 226-30. 

In a series of experiments, slabs of clay were compacted in the lab and then trimmed to produce cylindrical test specimens. One sample of the clay was compacted and then trimmed for a test specimen immediately, while the other was allowed to desiccate for a period of time before being trimmed. The one that desiccated had tiny cracks as a result of the desiccation process, and was much more permeable than the soil that had not been desiccated. As confining stress increased, the hydraulic conductivity decreased because the soil was compacted into a less porous condition. 

Although the sample that was cracked from desiccation was obviously more permeable, at a very high stress the hydraulic conductivities were essentially identical. With enough confining pressure acting on the soil, the cracks that had existed earlier closed up completely so that the soil was no longer highly permeable. 

Thermal/humidity stress testing involves exposing samples to various conditions of temperature and humidity. Once the conditions are chosen, the samples are placed in either ovens which control the conditions or saturated solutions of salts in desiccators. The physical appearance of the sample is important and should be monitored throughout the study. In addition, any loss or gain of water should be noted as well. 

To determine the effect of humidity on the stress, one sample (0% excess MDA) was placed in the oven with desiccant at 200°C for 6 hours, and the deflection was measured during that time span. The sample was next cooled to room temperature, weighed, and returned to the oven at 200°C the dish of desiccant was now replaced by a dish of water. The deflection as a function of time was again measured over a time span of 6 hours. The sample was cooled to room temperature and weighed again to determine percent weight gain. 

Ishida With respect to Ufespan, work by Paul Shaw on cjfi mutant flies showed that they became very sensitive to desiccation and sleep stress (Shaw et al 2002). cjfi flies died early after sleep deprivation. So the molecular mechanism of lifespan might be related to that of the circadian system. But another possibility is that BMALl and CLOCK regulate many other output factors, such as stress-sensitive proteins. 

Bacterial desiccation and survival of other species in dried soils and mineral powders has been reported (Bitton et al., 1976, Labeda et al., 1976 Dupler Baker, 1984 Moll Vestal, 1992). In many instances the authors did not report soil mineralogical characteristics however, Bitton et al. (1976) showed greater survival of Klebsiella aerogenes under desiccation stress when in soils dominated by montmorillonite as compared to kaolinite. Amendment of montmorillonite to a sandy soil also increased the survival of K. aerogenes and thus produced the greatest increase in survival in these studies as well as those conducted with rhizobia. 

Piatkowski, D., Schneider, K., Salamini, F. Bartels, D. (1990). Characterization of five abscisic acid-responsive cDNA clones isolated from the desiccation-tolerant plant Craterostigma plantagineum and their relationship to other water-stress genes. Plant Physiology 94, 1682-8. 

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