PLANT STRESS BY WATER DEFICIT: A REVIEW

Abstract

Water stress caused by water deficit limits the proper functioning of a plant due to low water availability. In natural systems, stress by water deficit can be the result of low rainfall, low water retention capacity of the soil, excessive salinity, extreme hot or cold temperatures, low atmospheric pressure steam or a combination of these factors. At a morphological level, the main symptoms are reduced plant height, stem diameter, biomass, leaf expansion, stem growth and root growth. At a physiological level, observed symptoms are stomatal closure, decreased water potential, turgor loss, reduced photosynthesis and limited gas exchange. The best known adaptations that plants have developed to reduce the effects of this kind of stress are deciduocity, leaves with thick cuticle, greater sap flux density, reduced leaf expansion and increased root growth. In agricultural systems, plant stress by water deficit leads to decreased crop yields. The calculation of water use efficiency (WUE) is a strategy to know the demand of water from a plant or crop under specific growth contitions. Efficiency can be evaluated at two levels: as the ratio between carbon fixed and water transpired (Photosynthetic Water Use Ufficiency, WUEph) or as the ratio between biomass produced and water used (Water Use Efficiency Productivity, WUEp).