Observation of water and Na+ in tissues of theBruguiera gymnorrhiza by1H-and23Na-NMR imaging

Distributions of free water, which is called water in this investigation, in mangrove (Bruguiera gymnorrhiza (L.) Lam.) tissues were examined by using¹H-NMR imaging, and accumulation of Na⁺ in hypocotyls was examined by using high resolution²³Na-NMR and²³Na-NMR imaging in relation to their morphology. Water located preferentially in the epidermis and the outer layer of cortex adjacent to the epidermis, and around vascular bundles of a root, a branch stem, and hypocotyls. Amount of water detected in the middle parts of cortex and pith was small unlikeAucuba japonica branch tissue. On the other hand, relatively high concentration of Na⁺ was detected in the pith besides the epidermis and the outer layer of the cortex adjacent to the epidermis, and around vascular bundles of the hypocotyl. The localization of Na⁺ did not correspond to that of water. Concentrations of Na⁺ accumulated (up to 22mM) in the hypocotyl were approximately 10 times higher than those observed in tissues of ordinary plants. The characteristic water distribution and accumulation of Na⁺ in the mangrove are considered to relate to their ecological nature for the adaptation to saline environments.