EFFECT OF P-STRESS ON GROWTH, PHOSPHORUS UPTAKE AND UTILIZATION EFFICIENCY OF DIFFERENT COTTON CULTIVARS

Phosphorus (P) availability is severely low in alkaline calcareous soils. Crop cultivars adopt morphological and physiological adaptation to maintain their normal growth under P stress conditions. Twelve cotton cultivars were grown in solution culture with two P levels (10 ~M & 100 ~M). Effect of P-Ievels and cultivars was observed on leaf area, shoot dry matter (SDM), root dry matter (RDM), root-shoot ratio, P concentration, P-uptake and P_ utilization efficiency. Phosphorus stress reduced the leaf area significantly among all the cotton cultivars and 52 % reduction in the leaf area was observed. Shoot dry matter and root dry matter was significantly affected by P_ levels and 32 % reduction in the SDM and 2-fold increase in the RDM was observed due to P-stress. There was highly significant positive correlation (r= 0.91 & r=0.75) between leaf area, SDM and RDM. Leaf-weight ratio of the P-stressed plants decrease by 5 % compared with adequate P-Ievel. Phosphorus stress decreased P_ concentration in both shoot and root highly significantly (70% and 61% respectively). Highly significant positive correlation (r=0.85) was found between SDM and shoot P-concentration. P-stress caused 7 % more assimilate partitioning to the roots as compare to the P-adequate level. Phosphorus stress reduced the P-uptake significantly and reduction was 81% and 53% in shoot and root respectively. Phosphorus stress caused preferential distribution of dry matter and P-concentration to roots as compared to the shoot indicated by highly positive correlation between RDM and root P-concentration.