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Title: PHOSPHORUS NUTRITION AND WATER STRESS EFFECTS ON PROLINE IN SORGHUM AND BEAN

Author
item AL-KARAKI G N - UNIV. OF NEBRASKA
item Clark, Ralph
item SULLIVAN C Y - 5440-20-00, RETIRED

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Phosphorus (P) deficiency and water stress (drought) can reduce plant growth and alter metabolic processes. The amino acid proline accumulates in leaves of many plants grown under water stress and is often used as an indicator of drought tolerance in plants. Drought-tolerant and drought-sensitive sorghum and bean plants were grown in soil with different levels of P with and without water stress to determine the effect of P and water stress on proline in leaves. Water stress caused proline to rise extensively in sorghum, and only small increases were noted in bean. Sorghum plants grown with higher P also had higher proline. This was not the case for bean. Proline accumulation in bean did not appear to be a specific indicator for plant adaptation to water stress as was noted for sorghum. Factors other than proline may be involved in bean adaptation to drought.

Technical Abstract: Phosphorus (P) deficiency and drought can reduce plant growth and alter metabolic processes like nitrogen metabolism. The amino acid proline (Prn) accumulates in leaves of many plants grown under water stress (WS). Two sorghum (Sorghum bicolor (L.) Moench) and two bean (Phaseolus vulgaris L. and P. acutifolius A. Gray) cultivars with different drought tolerances were grown in soil with different P levels with and without WS (water withheld) to determine effects of P nutrition and WS on Prn accumulation. Shoot dry matter (DM) increased with increasing P in soil. Leaves of water-stressed (+WS) sorghum and bean plants had lower P concentrations than non-stressed (-WS) plants, while leaves of +WS and -WS beans had similar P concentrations. Leaf diffusive resistance and water potential became greater in plants as WS severity increased compared to -WS plants, and became lower and nearly comparable to -WS plants 5 days after WS was relieved. Both species had higher Prn during +WS than under -WS but differed in response to added P. Sorghum leaves had highest Prn when grown with high P, while bean leaves had highest Prn when grown with low P. Five days after plants were relieved of WS, Prn concentrations in sorghum decreased and remained at relatively high levels, while Prn accumulation in bean decreased to -WS levels. High Prn concentrations in +WS sorghum leaves grown at high P levels might be an adaptive response to drought. Results indicated that Prn accumulation may not be an indicator of plant adaptive responses to drought in all plants. Adaptation of beans to WS may have been drought avoidance.