Winter stress

An intriguing stress-induced alteration in gene expression occurs in a succulent plant, Mesembryanthemum crystallinum, which switches its primary photosynthetic CO2 fixation pathway from C3 type to CAM (Crassulacean acid metabolism) type upon salt or drought stress (Winter, 1974 Chapter 8). Ostrem et al. (1987) have shown that the pathway switching involves an increase in the level of mRNA encoding phosphoenol-pyruvate carboxylase, a key enzyme in CAM photosynthesis. 

Working in level A proteetion ean eause a variety of stresses. The equipment is heavy. The pressure to eomplete work tasks during a time frame is intensified beeause work time is limited by air supply. Heat stress ean be a problem, even in the winter. In the summer, the use of eooling vests ean keep you eool but also adds to the weight that you are earry-ing. Typieally, all level A workers have a sharp knife blade so that they ean eut themselves out of the suit if the air supply fails. Realizing that you may have to eut yourself out of this suit in ease of air supply failure adds more potential stress to the situation. 

External Hooding Site specific requires detailed study Low winter lemperature Thermal stresses and embriirlcn icr.i. irc cmcred by design codes and stardijrLK ii i also see "ice."... 

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. 

Osmond, C.B., Winter, K. Powles, S.B. (1979). Adaptive significance of CO cycling in leaves of plants with different photosynthetic pathways. In Stress Physiology, ed. N.C. Turner and P.J. Kramer. New York Academic Press. 

Keim, D.L. Kronstad, W.E. (1981). Drought response of winter wheat cultivars under field stress conditions. Crop Science, 21,11-15. 

Improving Winter Cereals under Temperature and Soil Fertility Stresses, Proceedings of Cordoba Symposium, 1987 (in press). 

Calabrese A, Thurberg FP, Dawson MA, WenzlofF DR. 1975. Sublethal physiological stress induced by cadmium and mercury in the winter flounder (Pseudoplumnectes amer-icanus). In Koeman JH, Strik JJ, editors, Sublethal effects of toxic chemicals on aquatic animals. Amsterdam Elsevier. 

Calabrese, A., F.R Thurberg, M.A. Dawson, and D.R. Wenzloff. 1975. Sublethal physiological stress induced by cadmium and mercury in winter flounder, Pseudopleuronectes americanus. Pages 15-21 in J.H. Koeman and J.J.T.W.A. Strik (eds.). Sublethal Effects of Toxic Chemicals on Aquatic Animals, Elsevier Sci. Publ. Co., Amsterdam. 

Lemly, A.D. 1993c. Metabolic stress during winter increases the toxicity of selenium to fish. Aquat. Toxicol. 27 133-158. 

Vunkova-Radeva, R., Schiemann, J., Mendel, R.R., Salcheva, G., Georgieva, D. 1988. Stress and activity of molybdenum containing complex in winter wheat seeds. Plant Physiology, 87, 533-535. 

The nutritional value of the diet influences the ability of herbivores to detoxify plant secondary metabolites (Schwass and Finley, 1985). For instance, voles in winter have to consume the bark of birch Betula sp.). This causes stress and leads to poor growth and high mortality among young animals. Birch bark contains phenolics and terpenoids. Both are metabolized by cytochrome P450 monooxidases in phase I and conjugated with glucuronic acid in phase II. 

The effect of plant root exudation and exudation patterns on root colonization and expression of toxin production must be considered. For example, it may be important to determine the effect of root exudates from cold-stressed plants on these organisms, since the exudates apparently first appear just after the plants break winter dormancy (34). These data should provide information on root colonization potential, possible stimulation or reduction of toxin production, and mechanisms of plant resistance to the organisms. 

Phenolic compounds may be involved in plant responses to cold stress and in plant acclimation to low temperature. Acclimation of apple trees to cold climates was found to be associated with a seasonal accumulation of chlorogenic acid [102]. Strengthened frost tolerance in a variety of plants were attributed to thicker cell-wall lignification or suberization [102]. Thickening of cell walls and increased production of suberin-type lipids were observed in cold-acclimated winter rye leaves [103]. The presence of suberin in cell walls may favour membrane cell-wall adhesion, a major factor in the resistance of plant cells to freezing [104]. 

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