Role of active transport of potassium to leaves in the mechanisms of tolerance to salinity in common bean (Phaseolus vulgaris L.)

Abstract

Biochemical markers are of great utility in screening for salt tolerance of crops. In common beans (Phaseolus vulgaris), lower levels of proline under stress have been associated with a better stress resistance of cultivars. In the present study, the responses to salinity have been analysed in six cultivars of common beans: four local landraces from Spain and two experimental lines from Cuba. Proline was used for ranking the relative tolerance of the cultivars, confirming a previous study which reported as more stress-tolerant two of the Spanish landraces. Total soluble sugars concentrations varied with treatments and between genotypes, but it was difficult to assess their role in stress tolerance of the analysed plants. Sodium concentration in leaves was the lowest in one of the two salt-resistant cultivars, and potassium did not vary or even increased under salt stress in all of them, except for the most susceptible one, where a drop of this cation was registered under 150 mM NaCl. Changes in malondialdehyde (MDA) contents did not indicate salt-induced membrane peroxidation resulting from secondary oxidative stress; consequently, accumulation of total phenolic compounds and flavonoids, as an antioxidant defence mechanism, was not detected. These results highlight the reliability of using proline as a biochemical marker of salt stress in common beans and the importance of the mechanism related to potassium transport to leaves in conferring stress tolerance to some common bean cultivars.

Effect of the Pesticide Endosulfan and Two Different Biostimulants on the Stress Responses of Phaseolus leptostachyus Plants Grown in a Saline Soil

“…Furthermore, Pro can be considered a low-molecular-weight chaperon, which directly stabilises proteins and macromolecular structures, and is also a signalling molecule [68]. In common beans, Pro is a reliable stress biomarker, accumulating in direct proportion to the level of stress affecting the plants; that is, under the same stressful conditions, higher Pro concentrations are generally measured in the more sensitive genotypes [71][72][73][74]; this seems to be also the case in P. leptostachyus, according to the results of the PCA, where Pro levels are negatively correlated to plant growth parameters. In our experiments, the plants grown in the control soil, with and without endosulfan, appeared to be the most stressed as they showed the highest leaf Pro contents.…”