Efeitos da salinidade sobre o crescimento e acumulação de solutos inorgânicos em plantas jovens de cajueiro (Anacardium occidentale L).

Abstract

In order to identify and evaluate the range of salinity effects on the accumulation and distribution of K+, Na+, CI-, between shoots and roots, as well as on the N content and growth response, young cashew plants ( Anacardium occidentale L), with 22 days of age, were cultivated in sand, and irrigated daily with a nutrient solution with increasing concentrations of NaCI (0, 25, 50, 75 and 100 mol m-3), for a period of 30 days, under greenhouse conditions. The results obtained showed that the deleterious effect of salinity on the production and accumulation of total dry mass was proportional to the intensity of the concentrations of NaCI used. With increasing salinity, the internal concentrations of CI- and Na+ in shoots and roots reached levels incompatible with general metabolism. The internal concentrations of the K+ ion showed a slight tendency to increase in the shoot. In the roots, on the other hand, they were substantially reduced as a result of salinity. K+/Na+ selectivity, in shoots and roots, was drastically reduced especially at the highest level of NaCI. Typical symptoms of senescence, precociously induced by salinity, were observed 10 days after the beginning of the treatments, a fact that was confirmed by the reductions in the levels of total N in the shoots. The results obtained in this study indicate that cashew plants (CCP - 06) have a high degree of sensitivity to saline stress. This sensitivity, at least in part, seems to reflect an ionic imbalance resulting from the excessive accumulation of Na+ and CI- ions.