Effect Of Environmental Factors On Growth,Physiological And Biochemical Characteristics Of Caulerpa Lentillifera

Temperature,light intensity,salinity and nutrition concentration are important environmental factors affecting macroalgal growth,physiological and biochemical characteristics.Caulerpa lentillifera has high development value and broad market prospect.However,studies on the effect of environmental factors on its physiological and biochemical characteristics are rare.Therefore,this study adopted C.lentillifera as experimental material,aiming to examine the effect of changing environmental factors on its growth,physiological and biochemical characteristics and the regeneration capacity of its erect stem apical.We hope the biological and ecological characteristics of C.lentillifera can be revealed through this study.The main results were as follows:1.The treatments were controlled including two temperature conditions（22°C,low;27°C,normal）and three nitrate nitrogen concentration levels(4 mg·L^-1,low;16,mg·L^-1,medium,64mg·L^-1,high),in order to explore the responses of growth,physiological and biochemical characteristics in C.lentillifera to those different environmental conditions.Low temperature significantly reduced the RGR of alga,indicating the growth of alga was inhibited,but the alga had the higher Chl a and Car contents.Under low temperature,the activities of SOD and CAT in alga decreased first and then increased with the increase of nitrate nitrogen concentrations.Under normal temperature,SOD activity decreased while CAT activity increased with the increase of nitrate nitrogen concentrations.Under low temperature,low and medium nitrogen conditions inhibited Rd and Pmax of alga,while high nitrogen condition promoted Rd and Pmax of alga.Normal temperature with high nitrate nitrogen concentration significantly reduced Rd and Pmax.Results showed the growth in C.lentillifera had temperature dependency.Low temperature is not conducive to the growth and photosynthesis of algae.Increasing nitrate nitrogen concentration can alleviate the inhibition of low temperature on its photosynthesis.2.The treatments were controlled including two temperature conditions（22°C,low;27°C,normal）and three salinity levels（27‰,low;30‰,medium;33‰,high）,in order to explore the responses of growth,physiological and biochemical characteristics in C.lentillifera to those different environmental conditions.Compared with normal temperature,low temperature significantly inhibited the growth of C.lentillifera.Under normal temperature,salinity did not affect Chl a and Car contents,but high salinity level increased the activities of SOD and CAT activities.Low temperature with medium salinity level significantly increased the Pmax,αand Rd of C.lentillifera,but the contents of photosynthetic pigments（Chl a and Car）,Pmax and Rd of C.lentillifera decreased under high salinity level.At low temperature,CAT activity decreased first and then increased with the increase of salinity levels.Results showed the the growth of C.lentillifera had high temperature adaptability.Under normal temperature,the increase of salinity stimulated the antioxidant enzyme system of alga.Under low temperature,Medium salinity level is beneficial to increase the photosynthetic capacity of alga.3.The treatments were controlled three light intensity levels(40μmol·m^-2·s^-1,low;80mol·m^-2·s^-1,medium;120μmol·m^-2·s^-1,high),in order to explore the regeneration capacity in C.lentillifera erect stem apical.Low light intensity level was beneficial to the healing of the wound.However,the problem of this treatment was slower regenerate rate.High light intensity level increased regenerate rate and biomass of new alga.However,the color of the new alga was not green enough and other alga attached under this light condition.The results showed that light intensity levels had significantly effect on regenerate rate,morphology and quality of new alga.The method of low light healing with high light promotion can be considered to increase the yield in the future artificial breeding.4.The treatments were controlled three nitrate nitrogen concentration levels(4 mg·L^-1,low;16,mg·L^-1,medium,64 mg·L^-1,high),in order to explore the regeneration capacity in C.lentillifera erect stem apical.Under 16 mg·L^-1 treatment,the new alga had the best quality and highest biomass.The results showed nitrate nitrogen concentration levels had significantly effect on the quality of new alga.In conclusion,the growth and photosynthetic of C.lentillifera are affected by many environmental factors.Temperature is the most important factors affecting the growth.Low temperature inhibited growth and photosynthesis,but this stress can be alleviated by increasing nitrate nitrogen concentration or salinity level.On the other hand,the stem tip of erect stem has strong regenerative ability and can be regenerated into new alga within a week.Light intensity and nitrogen levels had effect on the quality of new alga.These studies would contribute to a deeper understanding of the effects of environmental factors on the physiological and ecological functions of C.lentillifera,and would provide important theoretical basises and scientific datas for high yield and efficient cultivation of C.lentillifera.