Drought stresses, plant responses

Recent studies by Wotton and Strange (8) provided circumstantial evidence for phytoalexin involvement in the resistance of peanuts to Aspergillus flavus. Their results indicated that resistance of peanut kernels to invasion by A. flavus was correlated with their capacity to synthesize phytoalexins as an early response to wounding. Also, conditions that promoted invasion of peanuts by A. flavus inhibited phytoalexin production. Thus, kernels of drought stressed plants, which are more susceptible to A. flavus than kernels of nondrought stressed plants, produced less phytoalexin in response to wounding by slicing than kernels from non-stressed plants. 

Claes, B., Dekeyser, R., Villarroel, R., Van den Bulcke, M., Bauw, G., Van Montagu, M. Caplan, A. (1990). Characterization of a rice gene showing organ-specific expression in response to salt stress and drought. The Plant Cell 2, 19-27. 

Similar defence responses are provoked by other forms of stress (eg, air pollutants, herbicides, cold or drought stress, etc.). Analogous responses were also observed during natural plant senescence. It is a challenging hypothesis that several kinds of stress factors demonstrate a common site of action at the subcellular level (Clijsters et al., 1990) and might accelerate the process of plant senescence (Lee et al., 1976a Van Assche et al., 1990). Its further evaluation, however, needs the continuation of research on senescence processes, stress effects and metal action at several levels of organisation. 

The loss of productivity of arable land due to desertification has induced intensive research into understanding plant responses to drought and salt stress. Osmotic stress causes changes in cell volume that can impact multiple levels of cellular organization and function including plasma membrane... 

Yamaguchi-Shinozaki, K., and Shinozaki, K., 1994, A novel c/.v-acting element in an Arabidopsis gene is involved in responsiveness to drought, low-temperature, or high-salt stress. Plant Cell 6 251-264. 

The timing of litterfall will also have a big impact on detrital processing and carbon dynamics in terrestrial ecosystems. Deciduous forests have a single annual pulse of fresh inputs in the fall, while evergreen coniferous and tropical forests have a somewhat continuous rate of litterfall which tends to fluctuate with water availability. Plants in grasslands and other semi-arid to arid ecosystems often turn over in response to drought stress. 

Wang W., Vinocur B., Altman A. Plant responses to drought, salinity and extreme temperatures towards genetic engineering for stress tolerance. Planta 2003 218(1) 1-... 

Impa SM., Nadaradjan S., Jagadish SVK. Drought Stress Induced Reactive Oxygen Species and Anti-oxidants in Plants. In Ahmad P., Prasad MNV. (ed.) Abiotic Stress Responses in Plants Metabolism, Productivity and Sustainability, Springer Sriencer Business Media 2012, p. 131-147. 

Anjum SA., Xie X-Y., Wang L-C., Saleem MF., Man C., Lei W. Morphological, physiological and biochemical responses of plants to drought stress. African Journal of Agricultural Research 2011 6(9) 2026-2032. 

Similarly to drought stress, sahnity imposes a water-deficit that results from the relatively high solute concentrations in the soil, but in addition it may cause ion-specific stresses resulting from altered K /Na ratios, and also may lead to a build-up in Na and d concentrations that are detrimental to plants. Plants respond to salinity using two different types of responses. Salt-sensitive plants restrict the uptake of salt and adjust their osmotic potential by the synthesis of compatible solutes (pro-hne, glycinebetaine, sugars, etc.) [19]. 

Fig. 10.1 Overview of plant responses to salinity and drought stresses. Stress signals activate several molecular responses to re-establish cellular homeostasis. The stress-responsive mechanisms include, selective ion transport across membranes of different cellular compartments, gene activation by specific transcription factors, synthesis of com-...

Soil anaerobiosis results in plant stress symptoms similar to those caused by drought stress. Among these are stomatal closure and reduction in net carbon assimilation. Photosynthesis in plants susceptible to flooding rapidly declines under anaerobiosis. Reduction in photosynthesis in response to flooding has also been reported for flood-tolerant species. 

Rizhsky, L, Liang, H, Shuman, (, Shulaev, V, Davletova, S, Mittler, R, When defense pathways collide. The response of Arabidopsis to a combination of drought and heat stress. Plant Physiol. 134, 1683-1696 (2004). 

Some authors(1) concluded that photosynthesis at low Fw was more limited by the loss of chloroplast activity than by increased difussive resistance. RBPC activity decreased in bean and cotton plants at water stress(2)(3) (4). PEPC and RBPC activities decreased at water stress in barley plants(5). In mesophyll cells from bean and tomato plants there was decreased in CO2 fixation at fairly low osmotic potentials which simultaneous with stomatal closure(6). Recently it was reported(7) that in soybean leaves a non stomatal limitations of leaf photosynthesis under drought stress conditions appears to be due in part to a reduction in the in vivo activity of RBPC. On the other hand it has been reported that chlorophyll content (8) (9) (10) shows alterations due to water stress. In the present work we pretend to compare the responses of carboxylase activities and chlorophyl content to water deficit in two maize hybrids (Ci ) (CPB2 and CPB8), two tomato cultivars (C3) (Pera Quibor, PQ and Rio Grande, RG) and two bean cultivars CC3)(Tacarigua,T and VUL-73-401,V). 

Subramanian KS, Santhanakrishnan P, Balasubramanian P (2006) Responses of field grown tomato plants to arbuscular mycorrfiizal fungal colonization under varying intensities of drought stress. Sci Hortic (Amsterdam) 107 245-253... 

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