Abstract
In this study, the effects of NaCl and CaCl2 on growth and nutrients uptake of cowpea (Vigna unguiculata L. Walp cvs. Mouola GG; Mouola PG, Garoua GG, Garoua PG and Tsacre) were investigated. Three treatments [0 (unsprayed), 50 mM NaCl or 50 mM CaCl2] were adopted, with five replications. NaCl and CaCl2 were applied as foliar spray twice a week during 30 days after sowing. Application of NaCl resulted in significant decreases in plant height, dry weights of root and shoot of Garoua GG, Mouola PG and Tsacre compared to Garoua PG and Mouola GG cultivars, while those growth parameters were significantly reduced under CaCl2 treatment in all cowpea cultivars except Mouola PG. K+, Ca2+ and Mg2+ contents decreased under NaCl stress in leaves of Garoua PG and Mouola GG, but no significant changes were observed in those of Garoua GG, Mouola PG and Tsacre. The main strategy of salt tolerance in Mouola GG and Garoua PG seems to be as a result of increased osmotic adjustment through the accumulation of Na+ in leaves while in salt sensitive Mouola PG, Garoua GG and Tsacre, the osmotic adjustment may be due to the accumulation of inorganic ions (K+, Ca2+ and Mg2+) in leaves, contributing to the maintenance of water uptake and cell turgor, allowing for physiological processes. In the analysis of growth parameters measured, the results suggested that Mouola GG and Garoua PG cultivars were relatively more tolerant to salinity than others, suggesting that those cultivars could be cultivated in the environment with varying salinity. CaCl2 treatment significantly increased growth parameters and nutrients uptake specially Ca2+ in Mouola PG cultivar, suggesting that it could grow and develop on calcareous soils.
Key word: Foliar spray, growth, nutrients uptake, saline and calcareous soils, Vigna unguiculata.
