Interação entre Na+ e K+ em plantas jovens de pinhão manso em condições de salinidade

Abstract

Salinity is a factor that limits crop growth and productivity and be associated with lack of K providing interactive stresses on plant nutrition. However, both the absorption and transport in the plant, comprising a sequence of processes that take place since the inüux of K and/or Na ; loading into the xylem for distribution or translocation by the various organs of the plant; redistribution across shoots and roots, and its efflux to the external enviroiunent. Understanding these processes is cmcial for the establishment of plants subjected to salt stress, especially under low K+ availability of. In order to characterize the mechanisms involved in absorption and transport of ions in the plant under saline conditions, several experiments were assembled in the presence of different concentrations of exogenous NaCl and KCl, depending on the purpose of each experiment. In the first experiment it was characterized the difference in the pattern of absorption and/or accumulation of K+ and Na+ submitted to increasing levels of K^. We emphasize that the provision of high concentrations of KT could alleviate the adverse effects caused by Na-r. The most favorable effects were associated with high selectivity of K^ in all plant organs. In the second experiment aiming to characterize differences in the pattern of absorption and partition of K+ and Na+, we found that K and Nar have sfrong differences in terms of transportation and distribution in saplings of Jatropha curcas. High concentrations of K in the external environment were able to reduce transport and toxic effects of NaT in leaves. Conversely, high levels of Na caused a reduction in the transport ofKT in different plant organs. The third experiment evaluated the combined effects ofKCl and NaCl on the uptake and transport ofNa and K at elevated temperatures. That the supply of high concentrations of K could alleviate the adverse effects caused by NaT. We can even say that physic nut plants were capable of retaining (or decrease in the absorption) of saline NaT ion by the root system with consequent restriction of the flow of these ions to the shoots of the plant, representing an important mechanism of resistance to salinity. In the fourth expenment evaluated beyond the effect of different temperatures, relative humidity in plants exposed to combined rates ofNaCl and KC1. Observed that in appropriate levels K'r and exposed to excess NaCl regardless of temperature and relative humidity high, reduce the adverse effects of excess sodium, possibly by reducing the transport of Na in to the xylem and less accumulation in the leaves. These data suggest that [KT]ext strongly promote the mitigation of the adverse effects of excess sodium and reduction of this ion in plants J. curcas.