Efeito dos estresses de seca e calor sobre pl?ntulas de pinh?o manso (jatropha cur cas L.)

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Biocombust?veis s?o um foco de discuss?o, ao que se trata de energias renov?veis. Quanto a esse ponto, atualmente discutisse a utiliza??o de zonas ?ridas para produ??o de biocombust?veis derivados de esp?cies oleaginosas resistentes ?s condi??es de aridez. A Jatropha curcas L. tem sido indicada como uma esp?cie potencial para esse tipo de utiliza??o, apontada pela literatura como resistente em condi??es desfavor?veis: seca e salinidade. Todavia, pouco ? descrito sobre sua resist?ncia a altas temperaturas e secas severas, principalmente sobre a sinergia de estresses combinados, cen?rio t?pico de regi?es semi?ridas. Este trabalho visa portanto avaliar os efeitos da temperatura sobre a J. curcas em condi??es de seca. O estresse h?drico foi aplicado utilizando duas concentra??es de PEG6000 dilu?das em solu??o hidrop?nica, induzindo potencial h?drico de -0,3 e -0,7 MPa. J? o estresse t?rmico foi conduzido em B.O.D. ? 40?C. Ap?s aplica??o dos estresses, o material vegetal foi coletado para avalia??o dos indicadores de estresse como conte?do relativo de ?gua (CRA) e dano de membrana (DM), al?m das determina??es bioqu?micas de prote?nas, amino?cidos totais (AALT), prolina (PRO) e glicina beta?na (GB), a??cares sol?veis totais (AST) e amido. Os resultados mostraram que o CRA pouco se altera, em condi??es de estresse e DM foi menor sob estresse t?rmico. Os solutos AALT, PRO e amido tiveram concentra??es mais significativas em folhas, enquanto que prote?nas, GB e AST foram mais significativas nas ra?zes. Quanto ? observa??o dos efeitos provocados pelo estresse h?drico, este trabalho fez compara??es a resultados semelhantes obtidos em outros estudos, refor?ando afirma??es sobre a efici?ncia das respostas da J. curcas em condi??es de seca. Todavia as plantas se mostraram mais suscept?veis ao estresse t?rmico, embora, quando em estresses combinados as respostas tenderam ao aumento em compara??o ao estresse t?rmico isolado. No geral, estes resultados abrem espa?o para que novos estudos sejam realizados a fim de testar os efeitos dos estresses combinados sobre a J. curcas e quais respostas a planta pode apresentara sob estas condi??es.

Biofuels are a focus of discussion when it comes to renewable energy. On this point, actually disc uss the use of arid zones for production of biofuels derived from oil plant species resistant to arid conditions. Jatropha curcas L. has been indicated as a potential species for this application, because it resistance to unfavorable conditions as: drought and salinity. However, a few studies have been described about its resistance to high temperatures and severe droughts, especially on the synergy of combined stresses, typical of semiarid lands. This study aims to evaluate the temperature effects of J. curcas on dry conditions. Water stress was caused using two concentrations of PEG6000 diluted in hydroponic solution, inducing water potentials of - 0.3 and - 0.7 MPa, while the heat stress was conducted in growth chamber at 40?C. After applying the stress, the plant material was collected for evaluation of stress indicators such as relative water content (RWC), membrane damage (MD) and absolute growth rate (AGR), and the biochemical determinations of proteins, total amino acids (TFAA), proline (PRO), glycine betaine (GB), total soluble sugars (TSA) and starch. The results showed that the RWC few changes in stress conditions and MD was lower under heat stress, probably due to the contribution of solutes such as protein and GB. Solutes TFAA, PRO and starch had more significant concentrations in leaves, while proteins, GB and TSA were more significant in the roots. TFAA and PRO were solutes with more significant responses on leaves, mainly in severe drought under heat stress. GB had an increase in the concentrations both in leaves and in roots, when under to drought and heat stress. Starch concentrations was reduced, which may be a reflex the reduction of AGR of the seedlings. The data suggest that J. curcas is able to withstand the effects of droughts tress, considering fewer changes of the CRA under the studied conditions. Overall the seedlings were more sensitive to heat stress. However, when combined the both drought and heat stresses, the results showed an increasing trend in relation to just heats tress.