| In order to discover the differences of response to seawater duress between Hibiscus hamabo Sieb.et Zucc.and Myrica cerifera, we devised a controlled experiment, which was based on the platform of wetland ecosystem research station that was located in gulf Hangzhou, to measure the indices of physiology, characteristics of photosynthesis and analyze the dissecting structure of leaves.The results showed that the change of photosynthetic characteristics under seawater flooding stress was the same betweent Hibiscus hamabo and Myrica cerifera. in the initial period of duress, the photosynthesize was decreased gradually as the delay of flooding time. At the same time the flooding stress mainly influence the restoration of photosynthesize for Hibiscus hamabo in the afternoon, but the stress had a strong effect on photosynthesize's peak of Myrica cerifera. The cause of photosynthesize's difference of the two kinds of plants under seawater flooding stress may concluded:(1)First, we found that the value of photosynthesize is determined by the value of T and Ci after the path anslysis of Pn and other factors. So, Ti and Ci influnence Pn directly.In additon, to Hibiscus hamabo the direct influence factors of the treatments which flooded 2 hours and 15 cm depth and flooded 4 hours and 25 cm depth are Tr and PAR. The direct influence factors of the treatments which flooded 6 hours and 35 cm depth and flooded 8 hours and 45 cm depth are Cond and Ci. To Myrica cerifera the direct influence factors of the treatments which flooded 2 hours and 15 cm depth and flooded 4 hours and 25 cm depth are Tr and Cond. The direct influence factors of the treatments which flooded 6 hours and 35 cm depth and flooded 8 hours and 45 cm depth are Ci and VPD.(2)We also found by research the content of chlorophyll a/b of Hibiscus hamabo Sieb.et Zucc increased then decreased first, afterwards increased gradually.It showed that chlorophyll b decomposed fast which meaned light harvesting complexes(LHC) decomposed fast. Hovever, photosystem reaction center decomposed slowly, which meaned plant could keep higher photosynthesis ability by adjusting the ratio of chlorophyll a and chlorophyll b.The content of chlorophyll a/b of Myrica cerifera increased then decreased, which showed LHC decomposed fast initially, then photosystem reaction center demoposed fast.(3)The more excess light energy which photosynthesis's drop caused might be eliminated by photorespiration and chlorophyll fluorescence in respiratory energy. Glycolate oxidase(GO) activity and photorespiration was the strongest of the Hibiscus hamabo Sieb.et Zucc and Myrica cerifera in the middle degree.So the ability of relieving light'damage was strongest. When flooding stress was stronger, GO activity was reduced significantly and the ability of resisting stress by photorespiration.Through observing chlorophyll fluorescence, NPQ of heat dissipation caused was increased. It meaned that more excess light energy was dissipated by qp under seawater stress.(4)In osmotic adjustment we found that Myrica cerifera could accumulate soluble sugar for storing engery active and intiative, in order to resist stress. Hovevery, the content of leaf's starch of Hibiscus hamabo Sieb.et Zucc was gradually increased in the main. The content of leaf's starch of Myrica cerifera was decreased greatly in L4 treatment. Meanwhile the soluble protein of Myrica cerifera was decreased earlier than that of Hibiscus hamabo Sieb.et Zucc. So Hibiscus hamabo Sieb.et Zucc was better than Myrica cerifera in the osmotic adjustment.Through the observation to the shape of Hibiscus hamabo and Myrica cerifera, the results showed that as the delay of flooding time, the degree of yellow was increased gradually and the growth of the plant and roots were subdued. The growth of adventitious roots of Hibiscus hamabo under the seawater flooding promoted the enlargement of Stem lenticel and the crossgrowth of the stem. Therefore, the ground diameter of plants in treatment groups were higher than those in control group. In addition, Hibiscus hamabo were capbale to sprout under seawater flooding and thus the number of shoot of Hibiscus hamabo in the H6 treament was obviously higher than other treatments.According to the lack of adventitious roots, the number of shoot, the height of seedling and the ground diameter were dicreased as the delay of flooding time.Therefore, by observing morphological indicators we can determine that the resistance to flooding of Hibiscus hamabo was stronger than Myrica cerifera... |
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