UV-B辐射对除菌和带菌米氏凯伦藻生长和生理生化特征的影响

Effects of UV-B irradiation on growth and physiological and biochemical characteristics of Kareoia mikimotoi before and after axenation

采用实验生态学和生物化学的方法研究了UV-B辐射对除菌前后米氏凯伦藻生长和生理生化特征的影响。结果显示:低剂量组(0.2、0.4、0.8J/m2)米氏凯伦藻藻细胞密度高于对照组;除菌藻高剂量组(1.6、3.2J/m2)无明显的指数生长期,带菌藻高剂量组可以维持一定的种群增长。除菌后低剂量组叶绿素a(Chlorophyll a,Chla)含量高于对照组,而带菌藻仅3.2J/m2组高于对照组。除菌后0.8、1.6、3.2J/m2剂量组胡萝卜素(carotene,Car)增长缓慢且低于对照组,带菌藻先增长、然后下降。可溶性蛋白含量在除菌前后的变化类似。除菌前、后超氧化物歧化酶(superoxide dismutase,SOD)活性均高于对照组,且呈现出一定的剂量效应。过氧化物酶(peroxidase,POD)活性在除菌前后变化相似,均在第3天和第6天增加到高于对照组水平。除菌藻丙二醛(malondialdehyde,MDA)含量高于对照组并随辐射剂量的增加而升高;带菌藻低剂量组在第6天和第9天下降至低于对照组水平。从除菌前后各生理生化特征来看,藻际细菌在防御UV-B辐射中起着一定的作用。

The effects of UV-B irradiation on growth and physiological and biochemical characteristics of axenic and nonaxenic Kareoia mikimotoi were studied by ecological and biochemical methods.The results show that algal cell densities of low-dose groups（0.2,0.4,0.8J/m2）are higher than those of the control groups.The high-dose groups of axenic K.mikimotoi have no evident exponential growth stage.However,the high-dose treatment groups of nonaxenic K.mikimotoi can maintain a certain population growth.Chlorophyll a（Chla）contents of low-dose groups of axenic K.mikimotoi are higher than those of control groups and those of K.mikimotoi are lower than the control groups except for 3.2J/m2 treatment group before axenation.Carotene（Car）contents of axenic algae（0.8,1.6,3.2J/m2 treatment groups）increase slowly and are always lower than those of control groups,and nonaxenic K.mikimotoi increases firstly and then decreases.The change of soluble protein contents is similar before and after axenation.Superoxide dismutase（SOD）activity of axenic K.mikimotoi in each treatment group is higher than that of the control groupss and showes a dose effect.The change of pod activities is similar between nonaxenic and axenic K.mikimotoi and both increase to above the control＇s level at 3dand 6d.Malondialdehyde（MDA）contents of axenic K.mikimotoi increase with increasing dose of UV-B irradiation,and those of low-dose treatment groups decrease to below the control＇s level at 6dand 9dbefore axenation.In addition to the activity of peroxidase（POD）,from the physiological and biochemical characteristics of K.mikimotoi before and after axenation,the data show nonaxenic algae have a strong defense capability and phycosphere bacteria plays a role in the defense of UV-B irradiation.