Coping With Water Shortage: An Update on the Role of K+, Cl-, and Water Membrane Transport Mechanisms on Drought Resistance

Abstract

Drought is now recognized as the abiotic stress that causes most problems in agriculture, mainly due to the strong water demand from intensive culture and the effects of climate change, especially in arid/semi-arid areas. When plants suffer from water deficit (WD), a plethora of negative physiological alterations such as cell turgor loss, reduction of CO 2 net assimilation rate, oxidative stress damage, and nutritional imbalances, among others, can lead to a decrease in the yield production and loss of commercial quality. Nutritional imbalances in plants grown under drought stress occur by decreasing water uptake and leaf transpiration, combined by alteration of nutrient uptake and long-distance transport processes. Plants try to counteract these effects by activating drought resistance mechanisms. Correct accumulation of salts and water constitutes an important portion of these mechanisms, in particular of those related to the cell osmotic adjustment and function of stomata. In recent years, molecular insights into the regulation of K + , Cl-, and water transport under drought have been gained. Therefore, this article brings an update on this topic. Moreover, agronomical practices that ameliorate drought symptoms of crops by improving nutrient homeostasis will also be presented.

A Wild Allele of Pyrroline-5-Carboxylate Synthase1 Leads to Proline Accumulation in Spikes and Leaves of Barley Contributing to Improved Performance Under Reduced Water Availability

“…In higher plants, the most rate-limiting enzyme for proline synthesis is pyrroline-5-carboxylate synthase ( Trovato et al, 2019 ). Proline biosynthesis occurs under both non-limiting and limiting growth conditions ( Cattivelli et al, 2011 ; Nieves-Cordones et al, 2019 ). Under non-limiting growth conditions, proline is used in protein biosynthesis to maintain the housekeeping function of the cell ( Hoffmann et al, 2017 ).…”

Chloride nutrition improves drought resistance by enhancing water deficit avoidance and tolerance mechanisms

“…Cl − fluxes are also relevant for adequate regulation of stomatal closure ( Nieves-Cordones et al , 2019 ) and specifically required for cell osmotic adjustment in response to osmotic stress ( Shabala and Lew, 2002 ). Therefore, through its role in the regulation of cell osmolarity, water balance, and WUE under well-watered conditions, Cl − homeostasis arises as a potential adaptive mechanism that might increase the ability of plants to withstand drought stress.…”

Chloride Improves Nitrate Utilization and NUE in Plants

“…Traditionally, chloride (Cl − ) has been considered an essential micronutrient for plants (White and Broadley, 2001;Broadley et al, 2012). But recently, Cl − has been uncovered as beneficial when accumulated to macronutrient levels in plant tissues (Franco-Navarro et al, 2016;Raven, 2017;Wege et al, 2017;Colmenero-Flores et al, 2019), with new biological functions that improve tissue water balance, whole-plant water relations, photosynthesis performance, and water-use efficiency (Franco-Navarro et al, 2016, 2019Nieves-Cordones et al, 2019). Chloride represents the dominant inorganic anion in the vacuole, with leaf contents that can be similar to those of the macronutrient K + , promoting cell osmoregulation, turgor-driven processes, leaf cell elongation, and a reduction in stomatal conductance (g s ; Franco-Navarro et al, 2016).…”