Metabolic Effects of Water Deficit in Crop Tropical Plants

Abstract

This work represents a compilation of research, undertaken in our laboratory in the past years, about the effects of water deficit on the photosynthetic metabolism, in tropical cultivars. In mesophyte plants the ability to adapt themselves metabolically to water deficit is an essential condition for survival.There have been many reports about the water deficit effects on decreased RBPC activity, it was reported (1) that the reversible decrease in the photsynthetic activity of the chloroplasts occurs at RCW values of 70 to 40% and this decrease is attributed to a reversible inhibitory effect on the enzymatic activity by the increase in cellular solute.It was reported (2) that RBPC activity decreased sharply whereas the Rubisco protein is affected to a lesser extent in maize plants under water. However, it has been reported (3) that in two sunflower hybrids under water stress, the primary sit of limitation of net photosynthesis might be related to concentraion of chlorophyll, total soluble protein or Rubisco protein.The aim of this work was to study the effects of water deficit on some enzyme activities such as Ribulose-1,5-bis-phosphate carboxylase (RBPC) and Phosphoenolpyruvate carboxylase (PEPC), on total chlorophyll content and on soluble protein content and the relationship between these parameters and components of leaf water status such as water potential and relative water content.