Aclimatação à salinidade induzida por nitroprussiato de sódio na germinação e no desenvolvimento inicial de plântulas de pinhão-manso

Abstract

The jatropha (Jatropha curcas L.) is an oilseed species, belonging to the family Euphorbiaceae, considered a good alternative to agricultural arid and semi-arid regions, such as the Brazilian Northeast. The soil salinization is a common problem in these regions, reducing the productivity of several crops, by negatively affect the growth and plant development. Therefore, it becomes important to carry out studies on the development of this species in salt stress conditions, as well as the assessment of the effects of nitric oxide (NO) in the induction of acclimation to salinity. This study evaluated the effects of pre-treatment of seeds with sodium nitroprusside (SNP), a compound that spontaneously releases NO in solution on germination and early development of jatropha seedlings in salt stress conditions. The concentration of NPS was set in a first experiment, in which jatropha seeds were germinated in germitest moistened sheets of paper with distilled water (pretreatment with water) or with NPS solutions of 50, 75, 100 and 200 M for a period of 24 hours (pre-treatment with SNP). Subsequently, the seeds were transferred to moistened sheets germitest with distilled water (control conditions) or 100 mM NaCl (saline treatment). After eight days after the pre-treatment (DAPT), the pretreated seedlings with NPS to 75 uM showed the best performance in saline conditions, mainly due to significant reductions in levels of Na + and lipid peroxidation, and the improvements in mobilization of reserves and growth. Based on this, we performed a second experiment, which aimed to confirm the observed results and expand the studies of pretreatment on physiology, biochemistry and molecular biology of jatropha plants under salt stress. Pretreatment of seeds with NPS to 75 uM resulted in better germination and mobilization of reserves, as well as further growth of seedlings in saline conditions, compared to non-pretreated. Furthermore, the pretreatment was a decrease in the accumulation of Na + and Cl- ions in saline stress conditions. Oxidative damage in the endosperm and embryo axis of jatropha seedlings were attenuated by pretreatment with NPS. This was due, at least in part, to induction of antioxidant system, both enzymatic, nonenzymatic as under conditions of salt stress, as well as the reduction in H2O2 concentration under these conditions. The analysis of gene expression of CAT and GR was consistent with the increase in activity of these enzymes, promoted by pretreatment with NPS under saline conditions. Based on these results, it is concluded that pretreatment with NPS was efficient in inducing acclimatization of jatropha seedlings to salt stress, mainly for allowing a better ionic and redox homeostasis.