Abstract
An understanding of plant-nutrient relationship is essential if the production of soybean in the saline soils of the world is to be made viable. Radiophosphorus (32P) and radiosodium (22Na) were administered to greenhouse-grown soybean plants (average height : 25 cm) cultured in Hoagland solution to investigate the uptake of phosphorus (P) and sodium (Na) as a function of increasing salinity from zero to 120 mM NaCl. P uptake depends on the concentration of inorganic P (Pi) in the nutrient medium. The addition of 8 mM Pi to the saline medium enhanced P accumulation significantly (p<0.01) by all plant parts. Polynomial regression equation expressed the relationship between 22Na activity and increasing salinity in leaves to be cubic (r2=1); a quadratic relationship prevcailed for the stem. The 32P activity versus increasing salinity was linear with a positive slope for the roots, but a negative slope for the the stem. Shoot and root dryweights decreased with increasing salinity. Leaf-chlorophyll content increased at low but decreased at high salinity levels. It is recommended that saline soils are fertilized with Pi to ameliorate salt-stress in soybean.
