Abstract
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. Key words: P-stress, cotton cultivars, leaf area, root shoot ratio
