Influence of water logging time on the growth of Kandelia candel seedlings

Influence of waterlogging time on the growth of Kandelia candel(L.) Druce seedlings grown for 70 d in the artificial-tidal tanks' simulated semidiumal tide under greenhouse is studied. Sand and soil act as the substrate and artificial sea-water with salinity of 15 is used in cultivation. Shorter waterlogging time (inundated for about 2~4 h) promotes thegrowth of K. candel seedlings, while longer time(inundated more than 8 h) or no waterlogging(0 h) inhibits theirgrowth. The number and length of aerating roots increase with the increase ofwaterlogging time. Under existing conditions, the optimal waterlogging time for the growth of K. candel seedlings is about 2~4 h in every tide cycle. Compared with other treatments, the 2 h sanded treatments obtain the highest biomass of seedlings, have the lowest massloss of hypocotyl and broaden the photosynthetic area by increasing the area per leaf after 70-d cultivation. And the soiltreatments have the similar tendeney. However, waterlogging for 8 h in every tide cycle is critieal for normal development of seedlings. K. candel seedlings are highly tolerant to waterlogging and a proper waterlogging is beneficial to thegrowth of K. candel seedlings.