How Plants Cope with Water Stress in the Field? Photosynthesis and Growth

Abstract

Plants are often subjected to periods of soil and atmospheric water deficit during their life cycle. The frequency of such phenomena is likely to increase in the future even outside today's arid/semi-arid regions. Plant responses to water scarcity are complex, involving deleterious and/or adaptive changes, and under field conditions these responses can be synergistically or antagonistically modified by the superimposition of other stresses. This complexity is illustrated using examples of woody and herbaceous species mostly from Mediterranean-type ecosystems, with strategies ranging from drought-avoidance, as in winter/spring annuals or in deep-rooted perennials, to the stress resistance of sclerophylls. Differences among species that can be traced to different capacities for water acquisition, rather than to differences in metabolism at a given water status, are described. Changes in the root : shoot ratio or the temporary accumulation of reserves in the stem are accompanied by alterations in nitrogen and carbon metabolism, the fine regulation of which is still largely unknown. At the leaf level, the dissipation of excitation energy through processes other than photosynthetic C-metabolism is an important defence mechanism under conditions of water stress and is accompanied by down-regulation of photochemistry and, in the longer term, of carbon metabolism.

Tolerance to water deficiency between two soybean cultivars: transgenic versus conventional

“…Insofar as the relative water content and water potential decrease, the photosynthetic rate of the leaves also decreases. This decrease is due to the stomata limiting the entrance of CO2, as well as restricting the photochemical and biochemical activities of photosynthesis (KAISER, 1987;CHAVES et al, 2002). The conventional cultivar showed a more expressive drop in Amax values under water deficit from 26 to 4.7 mol CO2 m -2 s -1 (81 %), while the Amax values in the transgenic cultivar show a 52% of decreasing ( Table 1).…”

“…However, environmental constrains has been causing a significant loss of productivity worldwide. Water deficiency is considered the main factor contributing to suboptimal crop productivity (CHAVES & OLIVEIRA, 2004 According to CHAVES et al (2002), water deficit may severely inhibit photosynthesis, due to the higher diffusive resistance to CO2 entry that results in a reduction in the intercellular CO2 concentration and, consequently, a decrease in the net assimilation of photosynthates, reducing crop yield. Prolonged periods of drought can directly affect soybean yield by reducing the plants' height, relative growth rate, leaf area index and photosynthetic rate.…”

Phenotypic plasticity and local adaptation favor range expansion of a Neotropical palm

“…Reduced root–shoot dry mass ratio may enhance initial growth and the competitive potential of seedlings in the Atlantic Rainforest, where we expect that light limitation—and not water—is the major driver of seedling mortality. Roots of temperate grassland species can change dramatically in weight and form in order for shoot growth rates to remain reasonably constant (Padilla et al., 2013), and different root–shoot ratios were found for woody and herbaceous species growing in contrasting conditions of water and light availability in Mediterranean‐type ecosystems (Chaves et al., 2002). However, the differential expression of root–shoot ratio by palm provenances in different tropical forest conditions remains unclear.…”

The effects of selenium and other micronutrients on the antioxidant activities and yield of corn (Zea mays L.) under drought stress

“…Environmental stresses, including drought, affect plant growth and yield production in different parts of the world (Chaves et al 2002). Drought stress may increase the formation of free oxygen radicals, hydrogen peroxide and hydroxyl radicals resulting in the degradation of membrane components, the oxidation of protein sulfhydryl (-SH) group and the loss of membrane functions (Yao et al 2009).…”