EFFECTS OF PHOSPHORUS AND WATER-STRESS LEVELS ON GROWTH AND PHOSPHORUS UPTAKE OF BEAN AND SORGHUM CULTIVARS

Primary determinants of crop production in arid/semiarid regions are lack of moisture and infertility, especially phosphorus (P) deficiency or unavailability. The effects of P and water stress (WS) levels on shoot and root dry matter (DM), leaf area, root volume, total root length, and shoot and root P concentrations and contents were determined in two bean [Phaseolus acutifolius Gray, cv 'Tepary #21' (''drought-resistant'') and P. vulgaris L., cv 'Emerson' (''drought-sensitive'')] and two sorghum [Sorghum bicolor (L.) Moench, cv SA7078 (''drought-resistant'') and 'Redlan' (''drought-sensitive'')] cultivars grown in nutrient solution. Plants were grown with different levels of P (20 and 100 mu M for bean and 20, 80, and 150 mu M for sorghum) when seedlings were transferred to nutrient solution, and WS levels of 0, 13.8, and 1 6.4% polyethylene glycol (PEG-8000) introduced after plants had grown in solution 23 days (bean) and 31 days (sorghum). All growth traits were lower when bean and sorghum plants were grown with WS and low P. Growth traits were higher in cultivars grown content, but not shoot P concentration, were lower when bean plants were grown with WS compared to without WS. Tepary #21 bean had higher shoot DM, leaf area, total root length, and shoot P concentration than Emerson when plants were grown with WS at each level of P. Sorghum shoot and root P concentrations were higher as P level increased regardless of WS, and WS had little effect on shoot P concentration, but root P concentration was higher. Contents of P were similar for SA7078 and Redlan regardless of P or WS treatment, but SA7078 had greater P contents than Redlan over all P and WS treatments. ''Drought-resistant'' cultivars generally had better growth traits, especially total and specific root lengths, than ''drought-sensitive'' cultivars.