Multiple traits associated with salt tolerance in lucerne: revealing the underlying cellular mechanisms

Abstract

Salinity tolerance is a complex trait inferring the orchestrated regulation of a large number of physiological and biochemical processes at various levels of plant structural organisation. It remains to be answered which mechanisms and processes are crucial for salt tolerance in lucerne (Medicago sativa L.). In this study, salinity effects on plant growth characteristics, pigment and nutrient composition, PSII photochemistry, leaf sap osmolality, changes in anatomical and electrophysiological characteristics of leaf mesophyll, and net ion fluxes in roots of several lucerne genotypes were analysed. Salinity levels ranged from 40 to ~200 mm NaCl, and were applied to either 2-month-old plants or to germinating seedlings for a period of between 4 and 12 weeks in a series of hydroponic, pot and field experiments. Overall, the results suggest that different lucerne genotypes employ at least two different mechanisms for salt tolerance. Sodium exclusion appeared to be the mechanism employed by at least one of the tolerant genotypes (Ameristand 801S). This cultivar had the lowest leaf thickness, as well as the lowest concentration of Na+ in the leaf tissue. The other tolerant genotype, L33, had much thicker leaves and almost twice the leaf Na+ concentration of Ameristand. Both cultivars showed much less depolarisation of leaf membrane potential than the sensitive cultivars and, thus, had better K+ retention ability in both root and leaf tissues. The implications of the above measurements for screening lucerne germplasm for salt tolerance are discussed.

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).…”

Shade does not ameliorate drought effects on the tree fern species Dicksonia antarctica and Cyathea australis

“…Sap was extracted as following: pinnae with several ball bearings of different diameters were placed into an Eppendorf vial with a perforated bottom. This vial was then mounted in a second vial and vials were centrifuged (12,000g for 3 min) to release bulk sap extract (nomenclature after Smethurst et al 2008). Sap collected in the second vial was then used for measurements.…”

Developing and validating a high-throughput assay for salinity tissue tolerance in wheat and barley

“…efflux from the cytosol in both root and leaf tissues and the overall salinity stress tolerance of various species was reported [e.g. barley (Chen et al 2005(Chen et al , 2007aWu et al 2013), 2015b), wheat (Cuin et al 2008;Wu et al 2013Wu et al , 2014, lucerne (Smethurst et al 2008) and poplar (Sun et al 2009)], the causal relationship between cytosolic K ? retention and vacuolar Na ?…”