Matching physiological traits and ion concentrations associated with salt stress in cowpea genotypes

Abstract

The salt tolerance of 25 cowpea genotypes (Vigna unguiculata L. Walp.) was studied during early vegetative growth. Salinity treatments were applied by irrigating with a nutrient solution containing 0, 85, and 170 mmol NaCl/L. Seedling survival decreased linearly as salinity increased, but this enabled cowpea genotypes to be ranked for salinity tolerance according to the magnitudes of slopes of regression of survival percentage on salinity. Sodium concentration was higher in roots than in shoots in all genotypes, and increased significantly in both roots and shoots as salinity increased. Chloride concentration in both roots and shoots increased with increasing salinity in all genotypes, and was higher in shoots than in roots at 85 and 170 mmol NaCl/L. In some cases, Ca, Mg, K, and P concentrations were reduced by an increase in salinity, but none of the genotypes appeared to suffer any nutrient deficiency. We observed wide differences in responses to salinity, and our results suggest that during the growth stage studied, 7 of the 25 genotppes tested could be classified as tolerant or relatively tolerant to salinity (Sonorense, CB3, CB27, Cuarenteño, CB46, Paceño, and IT82D-889).

Salt Tolerance is Associated with Differences in Ion Accumulation, Biomass Allocation and Photosynthesis in Cowpea Cultivars

“…Some mechanisms, such as reduced Na + delivery to the shoot, tissue‐ and organ‐specific Na + compartmentation and recirculation of Na + from the leaves back to the roots (Shabala and Cuin 2008) may be involved in this response. In any case, no evidence that salt tolerance in cowpea is related to differences in Cl − accumulation was found, contrary to what was previously documented by Murillo‐Amador et al. (2002b, 2006a).…”

“…In this study, we analysed the effects of moderate (non‐lethal) external salinity on growth and photosynthesis during the vegetative stage of two contrasting cowpea cultivars. Our results showed that improved salt tolerance may be primarily associated with restricted Na + accumulation in leaves, as had already been reported for cowpea (Murillo‐Amador et al. 2002b, Costa et al.…”

“…In this study, we analysed the effects of moderate (nonlethal) external salinity on growth and photosynthesis during the vegetative stage of two contrasting cowpea cultivars. Our results showed that improved salt tolerance may be primarily associated with restricted Na + accumulation in leaves, as had already been reported for cowpea (Murillo-Amador et al 2002b, Costa et al 2003, paralleling an absolute larger Na + concentration in roots, as shown for Pitiú ba. Some mechanisms, such as reduced Na + delivery to the shoot, tissue-and organ-specific Na + compartmentation and recirculation of Na + from the leaves back to the roots (Shabala and Cuin 2008) may be involved in this response.…”

Salinity Effects on Germination, Growth, Photosynthesis, and Ion Accumulation in Wild Miscanthus sinensis Anderss. Populations

“…Although Murillo-Amadot et al (2002) found that the chlorophyll content of salt-tolerant cowpea genotypes increased under salt stress, the chlorophyll content of M. sinensis decreased with increasing NaCl concentration and stress duration in the present study. This effect may be due to inhibition of chlorophyll synthesis or acceleration of its degradation as a result of salinity (Netondo et al, 2004b;Zhao et al, 2007).…”

Salt tolerance is unrelated to carbohydrate metabolism in cowpea cultivars

“…However, in contrast to other crops, scant information is available on its basic physiological processes involved in salt tolerance. Cowpea cultivars showing contrasting responses to salinity have been identified (Murillo-Amador et al 2002;Costa et al 2003;Murillo-Amador et al 2006); more recently, we suggested that salt tolerance could be associated with restricted Na ? accumulation in leaves, improved leaf area and increased photosynthetic rates per unit leaf mass in cowpea (Praxedes et al 2010).…”