桉树叶水浸出液对2种海洋微藻生长和叶绿素荧光特性的影响

运用水样叶绿素荧光仪(Water-PAM)研究了桉树叶水浸出液胁迫下湛江叉鞭金藻(Dicrateria zhanjiangensis)和纤细角毛藻(Chaetoceros gracilis)2种海洋微藻叶绿素荧光特性〔包括PS(光系统)Ⅱ的F_v/F₀(潜在活性)、F_v/F_m(最大光能转化效率)、Yield(实际光能转化效率)、ETR(电子传递效率),其中F_m和F₀分别为最大荧光和基础荧光〕的变化,同时监测微藻的生长情况,以研究桉树叶水浸出液对海洋微藻的影响,从而为探讨华南沿海大量种植桉树所造成潜在的海洋生态问题提供一些依据. 结果表明:①低浓度(以φ计,0.4、0.8、1.2mL/L)胁迫在96h内对湛江叉鞭金藻的上述4项荧光参数均无显著影响(P>0.05)；高浓度(2.0mL/L)胁迫下,24h时湛江叉鞭金藻的4项荧光参数都处于最低值,48h时处于次低值. 表明高浓度在胁迫早期(48h内)对湛江叉鞭金藻4项荧光参数有抑制作用,而后期(72、96h)这4项荧光参数又恢复到正常水平,抑制作用解除. ②低浓度(0.4、0.8mL/L)胁迫下纤细角毛藻的4项荧光参数在24、48h内均得到促进,而高浓度(2.0mL/L)胁迫下F_v/F_m在24h时为最小值,表现抑制作用；另外3项荧光参数则未受显著影响. 在胁迫后期(72、96h),纤细角毛藻的4项荧光参数均随着胁迫浓度的增大而增加,表现为促进作用. ③就生长情况而言,随着胁迫浓度的增大,2种海洋微藻细胞密度的增长明显变缓. 表明桉树叶水浸出液对2种海洋微藻的生长以及叶绿素荧光特性都有影响,从而将会对整个海洋生态系统产生影响. 

Effects of Aqueous Extract of Eucalyptus Leaves on the Growth and Chlorophyll Fluorescence Characteristics of Two Species of Marine Microalgae

Large-scale cultivation of eucalyptus has been seen along the coastal zone in Southern China in recent years. A number of studies have investigated the effect of eucalyptus allelopathic on land plants. However, little information is available about the impact of eucalyptus on marine primary productivity as well as the whole marine ecosystem. In the present study, we used the chlorophyll fluorescence technology (Water-PAM) to examine the changes of the chlorophyll fluorescence parameters (F_v/F_0, F_v/F_m, Yield and ETR) of Dicrateria zhanjiangensis and Chaetoceros gracilis, when they were exposed to aqueous extract of eucalyptus leaves. Meanwhile, the growth of two species of marine microalgae was observed during the exposure. The results showed that the low concentrations (e.g., 0.4,0.8,1.2mL/L) of the aqueous extract of eucalyptus leaves have little effect (P>0.05) on four chlorophyll fluorescence parameters of Dicrateria zhanjiangensis within 96h. High concentration (2.0mL/L) of the aqueous extract of eucalyptus leaves, however, could significantly affected the four chlorophyll fluorescence parameters of Dicrateria zhanjiangensis, which all reached the lowest values at 24h post-exposure and the second lowest at 48h post-exposure. Nevertheless, when the samples were treated with a high concentration of 2.0mL/L maintained for 72and 96h, the inbibitory effect of extract on chlorophyll fluorescence parameters disappeared. Apparently, higher concentrations (≥2.0mL/L) of the aqueous extract of eucalyptus leaves have an inhibitory effect on chlorophyll fluorescence parameters in the early stage of exposure (within 48h). For Chaetoceros gracilis, when it was exposed to low concentrations of 0.4and 0.8mL/L of the aqueous extract of eucalyptus leaves for 24and 48h, its four chlorophyll fluorescence parameters increased with concentrations used. However, when it was exposed to high concentration (2.0mL/L) of the aqueous extract of eucalyptus leaves, F_v/F_m of Chaetoceros gracilis reduced to the minimum at 24h post-exposure, whereas, the other three fluorescence parameters remained in the normal range. In the late stage of exposure (72and 96h), four chlorophyll fluorescence parameters of Chaetoceros gracilis increased with the concentrations. In addition, the aqueous extract of eucalyptus leaves has a significant inhibitory effect on growth of both two species of microalgae, as evidenced by the observation of a dose dependent inhibition of growth by aqueous extract. In conclusion, the study showed that the aqueous extract of eucalyptus leaves has significant effects on either growth or chlorophyll function of two species of marine microalgae. And thus, eucalyptus should have profound impact on the whole marine ecosystem.