In an attempt to identify the tolerant soybean genotypes based on biophysical parameters, leaf P content, PUE and acid phosphatase activity for phosphorus (P) limiting condition, a hydroponic culture experiment was laid out. Fifteen genotypes were grown in hydroponics with two treatments 50 and 100 per cent P. At 30 days, leaf P content (%), PUE (g dm /mg P), P uptake (mg/pl), photosynthetic rate, transpiration rate, conductance and water use efficiency were analyzed. The genotypes secreted higher acid phosphatase in P limiting condition. The P efficient/tolerant genotypes had higher photosynthetic efficiency.
The soybean genotypes Shivalik and CO-3 had significantly higher photosynthetic rates and were found better PUE genotypes. While MACS-58 was found efficient when phosphatase activity was considered. Based on P content and PUE, the genotypes ADT-1 & VL-soya-59 were found tolerant to P limiting condition. Shoot length, shoot dry weight, root dry weight decreased in P limited condition whereas root length and root to shoot ratio increased significantly and is one of the adaptive mechanism to overcome the P limiting condition in the soil.