The Physiological Response Of Marine Red Algae Gracilaria Lemaneiformis Under Environmental Stress

Marine economic red algae Gracilaria lemaneiformis has the advantages of wide survivaltemperature range, fast growth, large nutrition repository, improving the ecological environmentand high economic value. It is not only the production of high quality raw materials to product agar,but also very good food fiber source (it contain85%water-soluble dietary fibre).The activepolysaccharide and organic acid components of G.lemaneiformis have anti-tumor effect,phycobiliprotein has the functions of clearing free radicals and enhancing the immunity. In addition,G.lemaneiformis in breeding process can absorb a lot of nitrogen, phosphorus and carbon dioxideof sea water, release a large amount of oxygen, which can effectively purify culture zones, so it is akind of economic seaweed which has remarkable ecological benefit.This paper mainly studies the physiological response of G.lemaneiformis to differenttemperature stress and different salinity stress. The changes of the growth, cell ultrastructure,membrane permeability, antioxidative enzymes, lipid peroxidation, photosynthetic pigments andosmo-regulation substances were studied to reveal the stess physiological responses of the marinered algae G. lemaneiformis to low temperature (15℃), high temperature (33℃), normaltemperature (25℃) and low salinity (10‰), high salinity (35‰),normal salinity (25‰).Theresearch results are as follows:（1）Results showed that the adverse temperature stress inhibit the growth of G. lemaneiformis.Under two kinds of stress, the algal cell wall and chromatoplast were destroyed and theintracellular floridean starchs were accumulated. Under low temperature stress, the SOD activitydeclined to a certain degree, and the POD activity and MDA content showed no significantdifference compared with the control group. High temperature stress showed drastic influence on G.lemaneiformis with the SOD activity decreased significantly, and the POD activity and MDAcontent increased by95.82%and89.03%more than the control group in the later phase. Thecontent of the phycoerythrin, phycocyanin and chlorophyll a decreased to a certain degree, andthree photosynthetic pigments fell to an average of74.49%of the control group under lowtemperature stress, while51.48%under high temperature stress. The proline content increased by44.99%, but mannitol content had no significant change under low temperature stress. Under hightemperature stress, the content of proline increased by69.78%and those of mannitol increased by 34.47%in the later phase of the experiment.（2）Results showed that the adverse salinity stress inhibited the growth of G. lemaneiformis.The low salinity stress destroyed the Pit connection and caused intracellular floridean starchs indecline. The high salinity stress destroyed chromatoplast and caused accumulation of salt particles.The content of Na+,K+,Ca2+,Mg2+have no significant change under low salinity stress;but underhigh salinity tress,the Na+content rised and the contents of K+and Ca2+dropped, Mg2+content wasmore stable.The MDA content increased rapidly in the initial phase under two stresses, but SODand POD activity increased significantly in the later phase to clear the ROS of stresses. Thecontents of the phycoerythrin, phycocyanin and chlorophylla decreased to a certain degree in theinitial phase and then rebounded and stable in the later phase under low salinity stress.Under highsalinity stress, three kinds of photosynthetic pigment all have declined, the average dropped to71.80%of the control group. The content of proline decreased by21.11%, while those of mannitolincreased by19.61%under low salinity stress. Under high salinity stress, the content of proline andmannitol increased by75.66%and29.40%respectively.