Seasonal variation in the enzymatic activity of the source-sink system of rubber plants in a clonal garden

Ribulose-l,5-bisphosphate carboxylase oxygenase (rubisco) is a key enzyme in the reactions of co2 assimilation in plants. primary carbohydrates are converted into sucrose,which depends on the sucrose-p synthase (sps) as a pivotal enzyme. in rubber tree,sucrose hydrolysis can occur intensively in the laticiferous cells of the stem and depends on the invertase (inv) and sucrose synthase (susy) enzyme,producing reducing sugars,which are precursors of latex biosynthesis. the aim of this work was to evaluate seasonal changes in rubisco,sps,inv and susy activities of rubber plants in a clonal garden (rrim 600 and gt 1 clones),during warm/rainy and cold/dry seasons in lavras,minas gerais,brazil. the climatic differences in warm/rainy and cold/dry periods caused significant changes in all enzymatic activities evaluated. all enzymes had better performances in the warm/rainy period than in cold/dry. enzymatic activities seemed to be more affected by temperature changes than by precipitation decrease. © copyright by the rubber research institute of malaysia all rights reserved.