Efeito do Ca2+ externo no conteúdo de Na+e K+ em cajueiros expostos a salinidade Effect of external Ca2+ in the Na+ and K+ content in cashew exposed to salinity

Objetivando avaliar o efeito do Ca2+ externo na absor o e transporte de Na+ e K+ em plantulas de cajueiro an o precoce, expostas a altos níveis de NaCl, sementes do clone de cajueiro, CCP 06, foram germinadas e cultivadas em vermiculita dentro de casa de vegeta o. Plantulas com aproximadamente 8 folhas foram transferidas para condi es controladas de temperatura a 25±2 °C, U.R 80%, fotoperíodo de 12 h e 240 μmol m-2 s-1, onde elas foram divididas em dois ensaios. No primeiro as raízes foram destacadas da parte aérea e imersas em solu es de NaCl (0; 100; 200; 300; 400 mM) + CaCl2 (0,0; 0,3; 5,0 mM). No segundo ensaio plantulas intactas foram imersas em solu es de NaCl (0; 200 mM) + CaCl2 (0; 3 mM). As plantulas permaneceram nas solu es acima por um período de 48 horas. O NaCl aumentou a absor o e acúmulo de Na+ nos diversos órg o das plantulas, além de reduzir o conteúdo de K+ nas raízes e caules. A presen a de Ca2+ externo no meio contendo NaCl aumentou ainda mais a absor o e acúmulo de Na+ nos diversos órg os das mudas e também manteve o conteúdo de K+ nos órg os ao nível de tratamentos controles. O efeito do Ca2+ no aumento da absor o e transporte de Na+ permanece desconhecida. No entanto, esse efeito em plantulas de cajueiro submetidas a altas doses de NaCl está bem evidente. To evaluate the effect of external Ca2+ on Na+ and K+ absorption and transport in dwarf cashew seedlings exposed to high levels of NaCl, seeds of the cashew clone, CCP 06, were germinated and grown in vermiculite inside a greenhouse. Seedlings with about 8 leaves were transferred to controlled temperature conditions at 25±2°C, RH 80%, 12 h photoperiod and 240 μmol m-2 s-1, where they were divided into two trials. In the first one, the roots were detached from the shoot and immersed into NaCl solutions (0; 100; 200; 300; 400 mM) + CaCl2 (0.0; 0.3; 5.0 mM). In the second trial, intact seedlings were immersed in NaCl solutions (0; 200 mM) + CaCl2 (0; 3 mM). The seedlings remained in the solutions above for 48 hours period. The NaCl increased the Na+ absorption and accumulation in different organs of the seedlings and reduced the K+ content in the roots and stems. The presence of external Ca2+ in the environment with NaCl increased even more the Na+ absorption and accumulation in different organs of the seedlings and it also retained the K+ content in the organs at the level of the control treatments. The effect of Ca2+ in increasing the Na+ absorption and transport remains unknown. However, this effect on cashew plants seedlings exposed to high doses of NaCl is very evident