[Eco-physiological responses of high-latitude transplanted Aegiceras corniculatum seedlings to NaCl stress].

A sand culture pot experiment was conducted to study the eco-physiological responses of high-latitude transplanted mangrove Aegiceras corniculatum seedlings to varying concentration of NaCl (0, 100, 200, 300, and 400 mmol x L(-1)). Under the stress of 100 mmol NaCl x L(-1), the seedling growth was slightly promoted; whereas at 300 mmol NaCl x L(-1), the plant height, stem basal diameter, fresh and dry mass, and root/shoot ratio were decreased significantly. High salt stress inhibited the leaf superoxide dismutase (SOD) and peroxidase (POD) activities, increased the leaf malondialdehyde (MDA) content, and decreased the leaf chlorophyll and carotenoids contents as well as the total soluble sugar and free amino acid contents in different organs. Under the stress of different concentration NaCl, the Na+ contents in leaf, stem, and root increased rapidly while the K+ contents had a relatively decrease, resulting in a rapid decrease of K+/Na+ ratio and an imbalance between K+ and Na+ in A. corniculatum vegetative organs. When the NaCl concentration in the medium was higher than 300 mmol x L(-1), the C and N metabolism of A. corniculatum vegetative organs was maladjusted, which inhibited the normal growth of the seedlings, resulting in a significant decrease in the plant height and fresh and dry mass.

[Critical tidal level for Kandelia candel forestation in strong tidal range area].

Taking Ximen island of Yueqing bay, the biggest tidal range area among the coasts of China, as study site, an investigation was made on the survival rate, growth characteristics, and attached barnacles of 1- and 3-year-old Kandelia candel seedlings at the elevations 1.96, 1.66, 1.35, and 1.03 m above the zero tidal level of Yellow Sea. Significant differences were observed in the survival rate and growth situation of the seedlings among the elevations. There were two barnacle species, Balanus albicostatus and Balanus amphitrite amphitrite, and B. albicostatus was the major species which attached K. candel most seriously at elevation 1.35 m. The critical tidal level for K. candel in the site was 1.66 m above the zero tidal level, i.e., at least 1.29 m higher than the local mean sea level, and the flooding time per tide cycle being less than 3.65 h. Barnacle, strong tide, and extreme weather event were the main reasons for the higher critical tidal level.