BASIL IONIC RESPONSES TO SEAWATER STRESS AND THE IDENTIFICATION OF GLAND SALT SECRETION.

Basil (Ocimum Basilicum) seedlings were subjected to 0,5%,10%,20% and 40% seawater for 10 days under shade house conditions. Increasing seawater concentration led to considerable reduction in plant dry matter accumulation. However, root growth was not affected till treated with 40% seawater. Accumulations of Na+ and Cl^- were correlated with decline of Ca²+ and K+ in stems, roots or both. Contents of Ca²+ and K+ in leaves increased or remained relatively unchanged with increasing salt levels. In salinity-stressed plants, Na+ were partitioned mainly in roots and more than 50% of the K+ and Ca²+were stored in leaves. Higher K+/Na+ and Ca²⁺/Na⁺ ratios in leaves rather than in roots and stems were observed in Basil plants. Scanning electron microscopy coupled with X-ray microanalysis showed that Basil leaf gland secretions contained Na+ and Ca²+. The Na+ secretion increased while Ca²+ secretion decreased with the increasing seawater concentration. These results suggested that Basil salt tolerance is associated with the compartmentation of Na+ in roots and the balance of K+, Na+ and Ca²+ in leaves as well as the salt secretion by the leaf glands. [ABSTRACT FROM AUTHOR]