四列藻在营养限制胁迫下的超补偿生长研究

Over-compensatory growth of Tetraselmis tetrethele under the stress of nutrients deficiency

四列藻在营养限制胁迫下培养 1 0 d后 ,在恢复营养进行培养的初期 ( 1～ 5 d) ,表现出较强的超补偿生长能力。与持续正常营养培养的对照组比较 ,两者间的生长表现出显著差异 ( P<0 .0 5 )。四列藻超补偿生长的主要特征表现是在恢复营养进行培养的初期 ,处理组的藻细胞比对照组平均相对生长率提高 ,细胞数增多 ,叶绿素 a含量和生物量增高 ,细胞数净增率最高达 68.2 %～ 1 2 1 .1 % ,生物量净增率最高达 2 1 .8%～95 .3%。随着培养时间的推移 ,由于环境容量的限制 ,处理组与对照组之间的差异逐渐减小。到了培养的后期 ,处理组和对照组的各生长参数都趋于一致。同时发现 ,在受到营养限制胁迫后 ,藻细胞内蛋白质、细胞内糖和蛋白质 /糖 ( P/C)的比值发生了变化 ,但是在恢复营养进行培养 1 0 d后 ,均基本上恢复至处理前的水平。藻类中存在的这种超补偿生长特性有可能是引起藻华和赤潮的一个生物内在因素。

The phenomenon of over-compensatory growth was initially discovered among some higher animals and plants. Its concept is when an organism encounters some harmful environmental conditions such as nutrients deficiency, disease, and extreme temperatures, etc., its growth and physiological function will be affected and restrained, but when the stress is removed, the organism will grow fast than that under no stress. Normally, compensatory growth is categorized into three kinds, i.e. over-compensation, zero-compensation and under-compensation, based on the characters of recovery growth. Research on compensatory growth has covered ruminant animal, aquatic animal, and higher plant. However, there has done little research on micro-algae compensatory growth due to small size of micro-algae body and methodology limitation. In this paper, Tetraselmis tetrethele was used as experimental materials for studying the compensatory growth of micro-algae. Firstly, Tetraselmis tetrethele was cultured for ten days under the conditions of nutrients stress, i.e. poor nutrients, N deficiency, P deficiency, and N plus P deficiency, while normal nutrients condition (f/2 culture media) was served as control. Secondly, the nutrients stress was removed, the treated group and the control were simultaneously cultured for another ten days under conditions of same inoculative density and sufficient nutrients supply. Cell density, biomass, content of chlorophyll-a, intracellular protein and carbohydrate were analyzed and determined during these two periods. It was found that after subjecting to the nutrients stress, Tetraselmis tetrethele showed a strong ability of over-compensatory growth. The growth difference between the treated group and the control was significant (P<0.05). The main character of the over-compensatory growth of Tetraselmis tetrethele was that the treated group had higher average relative growth rate, more number of cells, higher biomass and higher chlorophyll-a content than those of the control group in the initial culture time(1～5 d), in addition, the maximal rate of net cells increase was 68.2%～121.1%, and the maximal rate of net biomass increase was 21.8%～95.3%. As the culture time proceeded, the difference between the treated group and the control decreased gradually. Eventually, all parameters of the treated group and the control trended to be equivalent. Whereas the intracellular protein, the intracellular carbohydrate and the ratio of protein to carbohydrate (P/C) changed under the nutrients stress, but all of them returned to their initial levels in the following culture after the stress being removed. Those results showed that over-compensatory growth might be an internal cause of algae bloom, and manipulation of over-compensatory growth could be used as guidance for controlling bloom of harmful algae and carrying out aquiculture of useful algae.