Effects of salinity on growth, water content and distribution of Na+ and K+ in the organs of Avicennia germinans L. seedlings

Effects of 4 different concentrations of NaCl on plant height, on water content and on the distribution of monovalent cations (Na + and K +) in organs of Avicennia germinans seedlings in semi-controlled conditions were investigated. After 4 weeks of cultivation, results showed that 200 mmoles sodium chloride reduced the height of leaves, but roots and stems growth was stimulated at 100 mmoles of NaCl. A high retention rate of sodium was noted in seedling epicotyl axes, contributing to delay the invasion of young leaves, thereby preventing toxic effects of the ion. Adaptation of mature leaves to the salt stress was found to be associated with succulence, which was achieved by the absorption of large quantities of water and K +. In leaves, uptake of K + was not affected by the NaCl concentration in the medium. As a result, absorption of Na + and K+ reduces the water potential, and consequently increases the water content in the studied organs. The high concentrations of Na + and K + in the leaves suggested that these ions might be the principal mineral elements responsible for the osmotic adjustment in the resistance of A. germinans to salinity stress. Keywords: mineral nutrition salinity, ionic transport, Avicennia germinans Cameroon Journal of Experimental Biology Vol. 1(1) 2005: 21-2