Effects Of Bap And Cr(Ⅵ) On The Growth And Ecophysiology Of Mangrove Kandelia Candle Seedlings

In this paper,Kandelia candel hypocotyls were cultivated in sand and treated with 15‰seawater for 40,60 and 110 days under laboratory conditions in a greenhouse.The influence of Bap(100,200,300,400,800μg·L^-1),Cr⁶⁺(0.5,2.5,5, 10,25,50mg·L^-1) single and combined pollution(5,10,25mg·L^-1 Cr⁶⁺;100,200, 300μg·L^-1 Bap) on the growth and physiological characteristics effect,including hypocotyls germination and growth,photosynthesis metabolism,water metabolism, soluble sugar,soluble protein,antioxidase membrane protection system were observed to inquire into the ecophysiological responses of mangrove K.candel to Bap,Cr⁶⁺ phytotoxicity.The results showed:1.The germination of K.candel seedlings was not obviously influenced by Bap pollution during the early germination period.When Bap concentration was lower than 400μg·L^-1,it was restrained in a shorter treatment time(40d).However Bap showed a acceleration on the growth at the level of 800μg·L^-1.The growth was promoted with increasing Bap concentrations in longer time(110d),correspondingly the biomass of various parts of K.candel seedling and the total biomass showed a increase.But biomass of leaves is decrease.The survival rate was 100%.2.The transpiration rate and the stomatal conductance of mature leaves of K. candel seedlings showed a crease with the increasing concentration of Bap, correspondingly the water contents of leaves were dropping.3.The change of the contents of chlorophyll a,chlorophyll b and total chlorophyll in leaves of K.candel seedlings with treatment time prolonged were decreased firstly and then increased at Bap concentration of 300μg·L^-1.The net photosynthetic rate of mature leaves was decreased.4.When hypocotyls were stressed 40 days,Bap had effect on the content of soluble proteins.The content of soluble proteins in roots were increased with the increasing concentration of Bap when treatment time prolonged.It showed a climb in leaves.The content of soluble sugar in roots and leaves was not influenced remarkable by Bap.5.The producing rate of superoxide in roots and leaves increased with the increase of Bap concentration and treatment time.6.The SOD activity and the POD activity of roots showed a climbe after 40 and 60 days.When treatment time prolonged to 110 days,they was restrained in roots and leaves.The Apx activity of roots was gradually increased and it was decreased in leaves with the increasing concentration of Bap.7.The ASA and GSH contents of roots in K.candel seedlings showed a climbe with the increasing Bap concentrations after 110 days.8.The germination of K.candel seedlings was obviously influenced by Cr⁶⁺ pollution.It was promoted under Cr⁶⁺ concentration of 2.Smg·L^-1,and reduced step by step when treatment time prolonged.When Cr⁶⁺ concentration was above 5mg·L^-1, the growth of K.candel seedling was restrained.Correspondingly the biomass of various parts in seedlings and total biomass showed a decrease.9.The transpiration rate was promoted and the stomatal conductance was restrained under Cr⁶⁺ concentration of 5mg·L^-1,the water contents of various parts in seedlings were gradually declining.10.The contents of chlorophyll was promoted with increasing concentration of Cr⁶⁺.With the increasing concentration of Cr⁶⁺ in the treatment time for 110 days, the net photosynthetic rate rapidly decreased.11.The content of soluble proteins in roots were decreased and it was increased in leaves when treatment time prolonged.The content of soluble sugar in roots and leavs was decreased with the increasing concentration of Cr⁶⁺ in the treatment time for 110 days.12.The producing rate of superoxide in roots was promoted at treatment of Cr.13.The SOD activity and the POD activity of roots increased in the treatment time for 110 days.The Apx activity of roots and leaves were decreased with the increasing concentration of Cr⁶⁺. 14.The ASA contents of leaves showed a climbe with the increasing Cr⁶⁺ concentrations after 110 days.15.Bap and Cr⁶⁺ combined pollution showed a significantly inhibition on hypocotyl germination.Compared with Bap stress and Cr⁶⁺ stress,the germination rate is less than the corresponding concentration Bap and 5mg·L^-1 Cr⁶⁺ and greater than 10mg·L^-1 Cr⁶⁺.The survival rate was higher than the corresponding concentration of Cr⁶⁺ after 110 days.16.With the treatment time extended to 110 d,Bap and Cr⁶⁺ combined pollution reduced the chlorophyll content,the net photosynthetic rate droped. Compared with Bap stress and Cr⁶⁺ stress,the chlorophyll content and net photosynthetic rate was less than the corresponding concentration Bap and larger than the corresponding concentration of Cr⁶⁺.17.The content of soluble proteins in roots were decreased and it was increased in leaves when treatment time prolonged.The content of soluble sugar in roots and leavs was decreased in the treatment time for 110 days.Compared with Bap stress and Cr⁶⁺ stress,they were larger than the corresponding concentration Bap and less than the corresponding concentration Cr⁶⁺.