Response Of Caulerpa Lentillifera To Low Temperature Stress And Screening Of Low Temperature Resistant Strains

Caulerpa lentilifera is a kind of large-scale economic green algae widely distributed in tropical areas,which belongs to Pteridophyta and Pteridophyta of Chlorophyta.The results show that the long stem grape fern algae is delicious and nutritious,which has high medical and health prospects and economic value.In recent years,with the improvement of people’s living standards,people’s demand for healthy food is growing day by day.In this study,we explored the growth and physiological changes of Caulerpa lentilifera in response to low temperature stress,and screened the low temperature tolerant strains in order to select the normal growth strains of Caulerpa lentilifera at low temperature:1.Effects of low temperature on the growth and morphological changes of staphylinium longumThe effects of different temperatures(15℃,21℃,27℃)on the growth and external morphology of staphylinium longipense were studied by temperature experiment.Algal changes: Caulerpa lentilifera could grow normally at 21℃ and 27℃,but 27℃was the most suitable temperature for growth.Caulerpa lentilifera showed negative growth at 15℃,and died completely after 6 days.Morphological changes: the morphology of Caulerpa lentilifera did not change significantly at 21℃ and 27℃.The morphology of Caulerpa lentilifera shrunk significantly at 15℃.With the progress of the experiment,the shrinkage of the algae became more obvious,causing irreversible damage.2.Effect of low temperature on photosynthesischlorophyll fluorescence : Through temperature experiment,it was found that the chlorophyll fluorescence parameters of Caulerpa lentilifera samples were maintained at about 0.78,at 21℃ and 27℃,and the change range was small,while the samples were in the low temperature at 15℃,the chlorophyll fluorescence parameters of the samples showed a rapid downward trend.With the continuation of the experiment,the chlorophyll fluorescence parameters of the samples decreased to below 0.2 at the third day,which caused irreversible damage to the samples.Chlorophyll content: through the temperature experiment,the chlorophyll content of the sample body fluctuates and rises when it grows at 27℃,while the chlorophyll content of the sample body grows at 21℃ is also on the rise,but its fluctuation range is large,and it is in the middle at 15℃,the chlorophyll content in the samples decreased first and then increased,which may be due to the accelerated decomposition of chlorophyll content in the algae samples at the beginning of the experiment.With the progress of the experiment,the algae samples lost a lot of water due to low temperature stress,resulting in the increase of the relative concentration of chlorophyll in the samples.3.Effects of low temperature on PhysiologicalIndexes of staphylinium longum: Through temperature experiment,the content of malondialdehyde of staphylinium longum was at a low level at 21℃ and 27℃,and the fluctuation was very small.The content of MDA in staphylinium longipectum at 15℃changed obviously.With the experiment,the content of MDA in the sample reached the peak on the 5th day,and then began to decline.This may be due to the rupture of the sample cells,causing irreversible damage to the algae strain,and it is unable to accurately determine the content of MDA in the sample.Peroxidase activity: through the temperature experiment,the change of peroxidase activity in the sample body is relatively gentle when it grows at 27℃,while the fluctuation range of peroxidase activity in the sample body is large when it grows at 21℃.The activity of peroxidase in the samples at 15℃ increased all the time,which indicated that the algae could resist the damage of low temperature by regulating the activity of peroxidase.Proline content: through the temperature experiment,the proline content in the body of Caulerpa lentilifera at 27℃ showed an upward and downward fluctuation trend,while the proline content in the body of the sample at 21℃ showed an upward and then downward trend at 15℃,the proline content in the body showed a rising trend,indicating that at this temperature,the samples have been synthesizing proline to resist the damage caused by low temperature.4.Screening of Pteridophyta strains with low temperature toleranceScreening of low temperature resistant staphylinium longipense strain in response to low temperature stress experiment,through 15℃ low temperature treatment,each batch of experiments will get several beads of good growth strains,the strain will be tied to the Changjiang extension base for propagation,and then after 15℃ low temperature treatment,so many times,the low temperature resistant strain is selected.Through the comparison of chlorophyll fluorescence and some physiological indexes between the same low temperature treatment and non-low temperature resistant strains.The variation trend of chlorophyll fluorescence and physiological parameters was similar at 27℃,which indicated that low temperature had little effect on the growth of low temperature tolerant lines,but low temperature had a significant effect on the growth of low temperature resistant lines.