GROWTH AND PHYSIOLOGICAL RESPONSES OF MANGROVE KANDELIA CANDEL (L.) DRUCE (RHIZOPHORACEAE) TO NAPHTHALENE EXPOSURE

The effect of naphthalene on growth and physiological responses of Kandelia candel (L.) Druce, a dominant species of subtropical mangroves in China, was investigated in sand culture. Root and leaf growth of seedlings were significantly reduced at higher levels of toxicant (1 mg/L and above). Stem growth was slightly stimulated at 0.1 and 1 mg/L naphthalene, and was reduced at 10 mg/L toxicant. Chlorophyll content and chlorophyll a/b ratios were increased with increased levels of toxicant. However, the significant declines in net photosynthetic rate were found with increased toxicant exposure. Both transpiration rate and stomatal conductance were stimulated at 0.1 mg/L naphthalene, and were reduced at higher levels of toxicant (1 mg/Land above). It appears that an adverse effect of naphthalene on mangrove K. candel seedlings may be found at the level of 1 mg/L and above.