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Title: THE CARBOHYDRATE METABOLISM ENZYMES SUCROSE-P SYNTHASE AND ADG-PYROPHOSPHORYLASE IN PHASEOLUS BEAN LEAVES ARE UP-REGULATED AT ELEVATED GROWTH CARBON DIOXIDE AND TEMPERATURE.

Author
item PRASAD, P.V. - UNIVERSITY OF FLORIDA
item BOOTE, K. - UNIVERSITY OF FLORIDA
item Vu, Joseph
item Allen Jr, Leon

Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2004
Publication Date: 6/15/2004
Citation: Prasad, P.V., Boote, K.J., Vu, J.C., Allen Jr, L.H. 2004. The carbohydrate metabolism enzymes sucrose-p synthase and adg-pyrophosphorylase in phaseolus bean leaves are up-regulated at elevated growth carbon dioxide and temperature. Plant Science. 166:1565-1573.

Interpretive Summary: Rising atmospheric carbon dioxide (CO2) and temperature will definitely influence growth and yield of many agricultural crop plants. Kidney bean, because of its high protein content, is an important pulse crop grown in many temperate, tropical and subtropical countries. In this study, by USDA,ARS scientists at the Center for Medical, Agricultural and Veterinary Entomology and University of Florida scientists in Gainesville, FL, kidney bean was grown for a season at ambient or twice-ambient CO2 and under daytime temperatures ranging from 28 to 40C. The purpose was to characterize the photosynthetic mechanisms of this agronomic crop under elevated growth CO2 and temperature. Photosynthesis is a process by which green leaves absorb CO2 from the air to make compounds necessary for plant growth. The results indicated that elevated CO2 enhanced leaf photosynthesis by 50%, as compared to growth at ambient CO2. In addition, elevated growth CO2 down-regulated the activity and concentration of Rubisco, the key protein in photosynthesis. This would allow an optimization of nitrogen use under elevated CO2 by reallocation of the nitrogen resources away from Rubisco. Besides, under elevated CO2, there was increased accumulation of soluble sugars and starch in the leaves, and this would be beneficial for plant growth. Thus, in the absence of other stresses, kidney bean photosynthesis would perform well under rising atmospheric CO2 and temperature as predicted for this century.

Technical Abstract: Kidney bean (Phaseolus vulgaris L. cv. Montcalm) was grown for a season in eight sunlit, environment-controlled chambers at day/night maximum/minimum air temperature regimes of 28/18, 31/21, 34/24, 37/27 and 40/30C under elevated [CO2] (700 ppm), and at 28/18, 34/24 and 40/30C under ambient [CO2] (360 ppm). As growth temperature increased from 28/18 to 40/30C, there was no damage on leaf photosynthetic rate (Pn) at ambient [CO2], whereas, at elevated [CO2] Pn was decreased by 15%. Elevated [CO2] enhanced Pn by 63, 53 and 48% at 28/18, 34/24 and 40/30C, respectively, as compared to ambient [CO2]. Growth at elevated temperature and [CO2] resulted in a down-regulation of the photosynthetic capacity, expressed through decreases in Rubisco activity, activation and protein concentration. There was no effect of elevated temperature and [CO2] on total soluble leaf protein. Elevated [CO2] increased concentrations of leaf soluble sugars and starch and activities of leaf sucrose phosphate synthase and ADPG pyrophosphorylase. This suggests that, at elevated [CO2], the reallocation of nitrogen away from Rubisco may lead to an enhancement in concentrations of other proteins. The up-regulation of carbohydrate metabolism would be beneficial for growth and yield of this crop species under rising atmospheric [CO2] as predicted for the coming decades.