Aspectos fisiológicos da produção de látex de seringueiras cultivadas em Nepomuceno - MG, em função da sazonalidade e da aplicação do ethrel®

Abstract

The south of Minas Gerais State (MG) has climatic characteristics favorable to the development and production of the rubber tree. The stimulant Ethrel ® has been widely used in commercial plantings of rubber trees, because it extends the latex flow and acts on regenerative processes of the bark increasing the productivity of dry rubber. Seasonal climatic variations such as temperature and precipitation affect the photosynthetic activity, and consequently the metabolism of carbon and nitrogen. These variations are the main interfering causes on latex production throughout the year. Following former evaluations of rubber tree productivity in southern Minas Gerais State, this work had the objective of evaluating the effects of the seasonal variation and the use of the stimulant Ethrel ® on the activity of different invertases isoforms in the bark and in latex C-serum, as well as their relationship with dry rubber production in RRIM 600 clone. Nutritional status, mineral and organic substances remobilization during leaves senescence of the same clone were evaluated. The experiment was conducted in an existing planting in the municipality of Nepomuceno, southern MG. We evaluated the effect of Ethrel ® stimulation on the activities of different invertase isoforms and on dry rubber productivity in cold/dry and hot/humid months. Hydric status and stem respiration of the plants were also evaluated. We analyzed the plants nutritional status and mineral and organic nutrients remobilization during leaf senescence which precedes defoliation. The RRIM 600 clone trees that received the stimulant showed higher production of rubber and lower index of obstruction in hot and humid period. The activities of acid invertase in vacuole, cytosolic neutral invertase in bark, and cytosolic neutral invertase in latex C-serum were higher in plants stimulated with Ethrel ® in hot and humid period, however bark neutral invertase activity was higher in cold and dry period. The activity of acid invertase in cellular wall was not influenced by the stimulant, but it was higher in hot and humid period. Respiration was higher in plants that received Ethrel ® in cold and dry period, but the stimulant did not showed effect in hot and humid period. Seasonal variation associated with Ethrel ® stimulant use caused changes in activities of different invertases isoforms, as well as in stem respiration activity. The plants showed a favorable nutritional status. Mineral nutrients N, P, K, S, Cu, and Fe were remobilized from leaves to other plants organs, as well as all carbohydrate, amino acids, and soluble proteins evaluated. Ca, Mg, B, Mn, and Zn were not remobilized.