| Abstract: | The effects of water stress on sucrose metabolism were evaluatedin bean plants of Tacarigua variety grown for 25 d. Decreasingwater potential and relative water content were observed. Waterstress effects resulted in a decrease of sucrose phosphate synthase(SPS) in both total (substrate saturating conditions) and Pi-insensitive(substrate limiting conditions plus inorganic phosphate) activities.The SPS Pi-insensitive activity was lower than the total SPSactivity, but the decrease in activity induced by water deficitwas relatively lower in the Pi-insensitive; however the activationstate increased during the water deficit period. An increasein sucrose synthase activity increased the activities of bothneutral and acid invertases at moderate water stress (0·8MPa) and decreased activities at severe water stress(1·45 MPa). The activity values of neutral invertasewere lower than those for the acid invertase. The starch/sucroseratio decreased and the ratio of total glucose/total fructoseincreased. These results indicate a relevant physiological roleof SPS in bean plants under water stress. Key words: Acid invertase, sucrose phosphate synthase, sucrose synthase |
