Screening plants for salt tolerance by measuring K⁺ flux: a case study for barley

Abstract

Development of salt-tolerant genotypes is central both to remediation of salinity-affected land and to meet increasing global food demand, which has been driving expansion of cropping into marginal areas. The bottleneck of any breeding programme is the lack of a reliable screening technique. This study tested the hypothesis that the ability of plants to retain K + under saline conditions is central to their salt tolerance. Using seven barley cultivars contrasting in salt tolerance (CM72, Numar, ZUG293, ZUG95, Franklin, Gairdner, ZUG403), a comprehensive study was undertaken of whole-plant (growth rate, biomass, net CO 2 assimilation, chlorophyll fluorescence, root and leaf elemental and water content) and cellular (net fluxes of H + , K + , Na + and Ca 2 + ) responses to various concentrations of NaCl (20-320 m M ). Na + selective microelectrodes were found to be unsuitable for screening purposes because of non-ideal selectivity of the commercially available Na + LIX. At the same time, our results show very strong negative correlation between the magnitude of K + efflux from the root and salt tolerance of a particular cultivar. K + efflux from the mature root zone of intact 3-day-old seedlings following 40 min pretreatment with 80 m M NaCl was found to be a reliable screening indicator for salinity tolerance in barley. As a faster and more cost-effective alternative to microelectrode measurements, a procedure was developed enabling rapid screening of large numbers of seedlings, based on amount of K + leaked from plant roots after exposure to NaCl.

Cell-Type-Specific H+-ATPase Activity in Root Tissues Enables K+ Retention and Mediates Acclimation of Barley (Hordeum vulgare) to Salinity Stress

“…1E). Mannitol treatment did not result in membrane depolarization but instead led to a slight hyperpolarization of the PM (Shabala and Lew, 2002) and resulted in an increased net K + uptake in both Arabidopsis (Shabala and Lew, 2002) and barley (Chen et al, 2005) roots. Consequently, upon mannitol treatment, no significant growth difference was observed between the apex and the mature zone (Fig.…”

Deregulation of apoplastic polyamine oxidase affects development and salt response of tobacco plants

“…High cytosolic K + is also required to maintain metabolic processes, such as protein synthesis by enabling tRNA binding to ribosomes (Chao et al, 2013 and references therein). A strong negative correlation between the magnitude of salt-induced K + loss and salt tolerance, suggests K + retention as a selection criterion between salt tolerant and sensitive varieties (Chen et al, 2005(Chen et al, , 2007a(Chen et al, , 2007bLu et al, 2013;Smethurst et al, 2008). Increase of Ca 2+ during abiotic and biotic stresses is required for tolerance in Arabidopsis (Johnson et al, 2014).…”

Arabidopsis root K+-efflux conductance activated by hydroxyl radicals: single-channel properties, genetic basis and involvement in stress-induced cell death

“…The ability of plants to retain a high K + /Na + ratio is crucial for salt tolerance (Chen et al, 2005;Volkov and Amtmann, 2006;Amtmann, 2009). Although some explanations for this phenomenon exist, they are clearly speculative (Shabala and Cuin, 2008).…”