Identificação de descritores fisiológicos em Jatropha Curcas L. submetida à salinidade

Abstract

One of the consequences of environmental degradation is soil salinization. In this context, it is estimated that in Brazil, of the 4.5 million hectares that are compromised by salinization, most located in the northeastern semi-arid region. A strategy to recover these degraded areas would be the insertion and proper handling of plant species such as Jatropha. Keeping in view the potential Jatropha, this study aimed to evaluate the physiological responses of seeds and Jatropha curcas L. seedlings subjected to salt stress. Two tests were performed at the Federal Rural University of Pernambuco, using seeds provided by Embrapa Agroenergy. In the test I the seeds were put in germistest paper and moistened with solutions 0, 50, 75 and 100 mM NaCl and placed in germinator. We evaluated the germination percentage, germination speed index, average germination time, shoot length, root and totality, fresh and dry weight of shoot, root and analysis of organic solutes. Already for the test II after germination in washed sand, plantlets were transferred to vessels containing 12 kg of washed sand. During the acclimation period they were watered with nutrient solution ½ strength Hoagland and Arnon and water. The experimental design was composed by the imposition of the same salt solutions than those used in the test I and two evaluation periods (15 and 30 days after differentiation of treatments). We analyzed the growth, gas exchange, water relations, the content of photosynthetic pigments and organic solutes. A reduction in the emergency speed index, initial growth and carbohydrates and proline of the jatropha root. The average time of germination is increased and also the organic solutes present in the shoot at the level of 75 mM NaCl. Salinity affects the germination performance of Jatropha seeds. In general, the variables related to growth, decreased from the level of 50 mM NaCl after 15 and 30 days of salt stress. Regarding gas exchange, Stomatal closure was was observed for the same level of salinity, being more pronounced in seedlings subjected to treatments of 75 and 100 mM NaCl, from 15 days of salt stress. For water relations, there are reductions in the TRA with increasing salinity in the two times of evaluation (4 and 12h). Similarly, after 30 days of salt stress, it was found reductions in photosynthetic pigments and chlorophyll content in all evaluated saline treatments. Regarding organic solutes, the levels of carbohydrates and amino acids in the leaves and roots were affected by salinity mainly in the levels of 75 and 100 mM NaCl, since proline was not indicative of stress for the species under study. Jatropha plants when subjected to salinity up to 100 mM NaCl has committed its initial development, but the species does not paralyze their growth.