Aspectos fisiológicos e bioquímicos de Jatropha curcas L. cultivada sob estresse salino

Abstract

In Brazil, with the advent of the Brazilian Biodiesel Program and emergence of high demand for vegetable oils, the pinion gentle has been disclosed as an alternative for the raw material supply. However, encouraging the planting of large areas in pinion gentle causes great concern to practitioners involved with agricultural research in Brazil, due to limitation of the technical knowledge for this culture. The irrigation practice it’s an effective instrument in the productivity increasing and expansion of agricultural frontiers, but when improperly used can be cause problems of the soil salts excess, especially in arid and semi-earid regions, reducing the crop yield. The edafoclimatic conditions of these regions and the anthropic action also provide the soils salinization. Soil salinity can be reach harmful levels to plants grown in a short time period and depending of the vegetable species the injuries have varying severity degrees. Before the above, the present study aimed to evaluate the physiological and biochemical responses of pinion gentle (Jatropha curcas L.) under saline conditions. Seven treatments were established: 0, 15, 30, 45, 60, 75 and 90 mol.m-3 of NaCl. The plant growth was evaluated by determination of the leaves number (LN), leaf area (LA), fresh and dry matter total production (FMT and DMT), absolute and relative growth rate (AGR and RGR). Were analyzed, in leaf tissues, the proline tenors, total soluble carbohydrates, total phenols, total soluble proteins, as well as, the absolute integrity, relative integrity and cells membrane damage percentages. The Na+, K+ and Cl- levels determination was also performed in plants leaves, stems and roots. The experimental design was completely randomized with five replicates, totaling 35 experimental units during the period of 28 days. Increased salinity reduced plant growth in all variables. Leaf area was reduced from the concentration of 45 mol.m-3 NaCl and the fresh and dry matter production and the growth rate from the 60 mol.m-3 NaCl. Was observed an elevation in Na+ and Cl- levels in the leaves well as in the stem and root, and the K+ levels reduction in leaves and roots with the salt concentration increased in nutritive solution. The soluble carbohydrates concentration increased significantly only in plants subjected to 30 mol.m-3 of NaCl and the soluble protein content in concentrations of the 15 to 30 mol.m-3 of NaCl. The total phenols content increased in plants treated with NaCl concentration equal or higher to 30 mol.m-3 of NaCl. It was observed a membrane integrity reduction only in the most severe salinity concentrations. The organic solutes accumulation was concomitant to decrease in the growth. The Na+ and Cl- high levels indicate the absence of extrusion mechanisms for these ions as well as translocation to the shoot.