Phytomass accumulation and mineral composition of cowpea (Vigna unguiculata) under salt stress and phosphate fertilization

Abstract

This study aimed to evaluate the effect of irrigation with saline water and phosphate fertilization on phytomass accumulation and tissue mineral composition of cowpea shoots. The research was carried out in a greenhouse utilizing randomized block design in a 5 x 3 factorial scheme consisting of five levels salinity of irrigation water (0.5 as control, 1.5, 2.5 3.5 and 4.5 dS m-1) and three doses of P2O5- (60, 100 and 140% from a recommended dose of 60 kg P2O5- ha-1), with 5 replicates. The plants were grown in pots up to flowering and then phytomass accumulation and mineral composition of cowpea (indicate cultivar name) shoot were measured. Irrigation with saline water from 0.8 dS m-1 reduced phytomass accumulation and mineral composition of cowpea plants, making the plants to be considered moderately tolerant up to EC 2.5 dS m-1. The 40% increase in recommended phosphorus dose promotes high iron and copper accumulations and, less sodium accumulation into tissues of cowpea shoot as influenced by saline stress. 60% reduction of the recommended dose of phosphate fertilizer increased the manganese and zinc accumulation of tissues of cowpea shoot under salt stress.

Photosynthetic Responses, Growth, Production, and Tolerance of Traditional Varieties of Cowpea under Salt Stress

“…Roxão was the only variety without SDM modifications caused by salinity and was unique in the susceptible group with an investment in biomass at the expense of grain production. The authors in [ 7 , 8 , 24 , 25 ] and other authors observed reduced growth and biomass accumulation in cowpea beans under salt stress. These reductions are part of the acclimation process of cowpea bean plants that have the potential to tolerate salt stress as they seek to secure production and perpetuate the species.…”

“…The A N reductions were related to stomatal factors, i.e., the reduction of stomatal conductance limited the influx of CO 2 and consequently the internal concentration of CO 2 ( Ci ) in the substomatal cavity, reducing water absorption and transpiration [ 6 , 17 , 18 ]. The reduction of stomatal conductance occurred with increased soil salt concentrations and led to a decrease in osmotic and water potentials, resulting in toxicity of specific ions—Na + and Cl - [ 5 , 8 , 9 ]. Plants experience issues absorbing water from the soil under salt stress and tend to reduce water loss by closing stomates and reducing transpiration [ 6 , 18 ].…”

“…Water with a high sodium adsorption ratio (SAR) can modify the physicochemical conditions of the soil, and excess soluble salts result in lower osmotic potential, water deficit, stomatal closure, limited CO 2 assimilation/water usage, and alterations to the photochemical process [ 5 , 6 ]. Osmotic restrictions combined with ionic restrictions and nutritional imbalance limit gas exchange and biomass accumulation and production [ 5 , 6 , 7 , 8 ]. The decrease in productivity of cowpea under saline stress occurs due to the decrease in the water potential, survival rate, plant’s initial vigor, growth, and photosynthetic activity and excessive accumulation of Cl and Na ions and reactive oxygen species (ROS) [ 5 , 6 , 7 , 8 , 9 , 10 , 11 ].…”

“…Osmotic restrictions combined with ionic restrictions and nutritional imbalance limit gas exchange and biomass accumulation and production [ 5 , 6 , 7 , 8 ]. The decrease in productivity of cowpea under saline stress occurs due to the decrease in the water potential, survival rate, plant’s initial vigor, growth, and photosynthetic activity and excessive accumulation of Cl and Na ions and reactive oxygen species (ROS) [ 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. Therefore, studies that evaluate gas exchange and photosynthetic efficiency are important for the identification of salinity-tolerant plants.…”