Plant Science 166 (2004) 1565–1573 The carbohydrate metabolism enzymes sucrose-P synthase and ADG-pyrophosphorylase in phaseolus bean leaves are up-regulated at elevated growth carbon dioxide and temperature P.V. Vara Prasad a,∗ , Kenneth J. Boote a , Joseph C.V. Vu b , L. Hartwell Allen, Jr. b a Agronomy Department, University of Florida, 304 Newell Hall, Gainesville, FL 32611, USA b Agricultural Research Service, United States Department of Agriculture, Gainesville, FL 32611, USA Received 1 November 2003; received in revised form 13 February 2004; accepted 13 February 2004 Abstract Kidney bean (Phaseolus vulgaris L. cv. Montcalm) plants were grown under daytime maximum/nighttime minimum temperatures of 28/18, 34/24 and 40/30 ◦ C at ambient carbon dioxide concentration (CO 2 ; 350 mol mol -1 ), and 28/18, 31/21, 34/24, 37/27 and 40/30 ◦ C at elevated (twice-ambient) CO 2 , to characterize how increases in growth CO 2 and temperature affected kidney bean leaf photosynthesis and carbohydrate metabolism. Elevated CO 2 enhanced leaf photosynthetic rates by about 57% across the temperature regimes, compared with plants grown an ambient CO 2 . As growth temperature increased from 28/18 to 40/30 ◦ C, leaf photosynthetic rates decreased at both ambient and elevated CO 2 . Growth at either elevated temperature or CO 2 decreased activity, protein content and activation of the primary photosynthetic enzyme ribulose 1,5-bisphosphate carboxylase-oxygenase (Rubisco). Elevated CO 2 increased activities of sucrose-phosphate synthase (SPS) and adenosine-5 ′ -diphosphoglucose pyrophosphorylase (AGP) and accumulation of soluble sugars and starch across all temperatures, compared with plants grown at ambient CO 2 . At elevated CO 2 , growth temperatures above 34/24 ◦ C significantly increased leaf carbohydrates (total soluble sugars and starch) and activity of AGP. The up-regulation of leaf carbohydrate metabolism enzymes under elevated CO 2 plus temperature would be beneficial for growth and productivity of kidney bean in future climates. © 2004 Elsevier Ireland Ltd. All rights reserved. Keywords: Carbon dioxide; Carbohydrate; SPS; AGP; Rubisco; Photosynthesis 1. Introduction At the present rates of greenhouse gas emissions, atmo- spheric carbon dioxide concentration (CO 2 ) is expected to reach more than twice the pre-industrial concentration by the end of this century [1]. In addition, climate models pre- dict that the doubling of CO 2 will increase the global av- erage surface air temperatures by 1.4 to 5.8 ◦ C [1,2]. These changes in CO 2 and temperature will not only influence cli- mate but also the physiological processes, including pho- tosynthesis, carbohydrate metabolism, growth and yield of agricultural crop plants. Leaf photosynthesis in C 3 plants is influenced by the primary carbon fixation enzyme ribulose-1,5-bisphosphate ∗ Corresponding author. Tel.: +1-352-3921811x232; fax: +1-352-392-1840. E-mail addresses: vpaga@mail.ifas.ufl.edu, vvpagadala@hotmail.com (P.V.V.Prasad). carboxylase-oxygenase (Rubisco) as well as by the ac- cumulation and metabolism of carbohydrates in the leaf and source-sink balance [3,4]. Long-term exposure to ele- vated CO 2 often results in down-regulation of Rubisco [3]. Detailed survey by Long and Drake [5] showed that, on average, elevated CO 2 decreased both Rubisco content and activity in the range of 8 to 15% in plants grown in pots and large rooting volumes. Similarly, increases in air tempera- tures to the extent of 5–6 ◦ C above present ambient levels is known to influence photosynthesis, Rubisco content and carbohydrate metabolism [3,6]. Phaseolus bean is an important grain legume crop and a rich source of protein and carbohydrates for human popu- lations across the globe. Elevated CO 2 caused increases in leaf photosynthetic rates of bean in some studies [7,8], while others have observed no beneficial effects [9–11]. In potted bean plants, CO 2 enrichment (700 mol mol -1 ) compared to ambient (360 mol CO 2 mol -1 ) increased net carbon as- similation rates early in the season, but from 25 days after 0168-9452/$ – see front matter © 2004 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.plantsci.2004.02.009