荔枝落叶对铜绿微囊藻生长和光合作用的影响

Effects of Litchi chinensis Defoliation on Growth and Photosynthesis of Microcystis aeruginosa

利用浮游植物荧光分类仪对暴露于不同浓度荔枝落叶浸出液下铜绿微囊藻的生长、最大光合作用效率(Fv/Fm)、实际光合作用效率(YⅡ)、光能利用效率(α)、最大相对电子传递速率(r ETRmax)和光饱和系数(Ik)进行了为期15 d的检测,研究浸出液对铜绿微囊藻生长和光合作用的影响.结果发现,浸泡5 d的荔枝落叶浸出液可以抑制藻的生长,呈明显的浓度抑制型变化,随着时间的延长,抑制作用下滑.荧光参数Fv/Fm、YⅡ和α与浸出液浓度由负相关转为正相关或保持正相关关系,浸出液可能早期对藻光合作用发生胁迫,或通过提高光能利用效率来度过胁迫环境,r ETRmax、Ik和叶绿素a浓度与浸出液浓度由负相关转为显著负相关关系.三维荧光图谱结果表明,第15 d时,在投量为2.0 g·L-1时,色氨酸及酪氨酸荧光峰强度约为1.2g·L-1投量情况下的1/3,同时腐殖酸的荧光峰强度减弱.进一步研究藻细胞生长的半抑制浓度EC50值表明,与传统的农作物秸秆控藻比较,其EC50值较低,可能荔枝落叶化感控藻效果较强,只需较低的浸出液浓度而能达到较好的控藻效果.

The growth and physiology of bloom-forming cyanobacterium Microcystis aeruginosa were determined by the pulse amplitude modulated fluorimetry when exposed to different concentrations of Litchi chinensis defoliation extract for 15 d. The growth,maximal efficiency( Fv/ Fm),effective quantum yield( YⅡ) of PSⅡ photochemistry,photosynthesis efficiency( α),maximum electron transport rate( r ETRmax) and light saturation coefficient( Ik) were used to evaluate the growth and photosynthesis in M. aeruginosa.It was found that the extract of L. chinensis defoliation stored for 5 days significantly inhibited the growth of M. aeruginosa in a concentration-dependent way. After a long time of exposure,stimulation effect disappeared gradually. Fv/ Fmfluorescence parameters,YⅡ and alpha changed from negative correlation to positive correlation or kept positive correlation with the extract of L. chinensis defoliation,which might affect the photosynthesis of M. aeruginosa at early time or help the cyanobacterium to survive in the stress environment by improving the efficiency of light energy. Ik,r ETRmax and the content of algal chlorophyll-a changed from negative to significant negative correlation with the extract. Three-dimensional fluorescence spectra showed that the peak intensities of tryptophan and tyrosine fluorescence were only about one third in 2. 0 g·L- 1extract treatment when compared to the 1. 2 g·L- 1extract treatment on day 15. At the same time,the peak intensity of humic acid fluorescence was weaker than that on day 1. Further study showed that the EC50 of algal growth was smaller than that of the traditional crops straw,which might achieve good effect to control the growth of algae with lower concentration of L. chinensis defoliation extract due to its strong allelopathy.