红树植物根系分泌物壬二酸对海洋原甲藻的影响

一般认为植物根际微生物的生物量高于非根际,这与植物根际分泌多种物质有关。不同种类的红树林内出现不同程度的林内富营养化现象,浮游藻类生物量很高,认为这部分地与红树植物根系分泌物(Root Exudates,REs)对林内生物的调控作用有关。红树植物根系分泌物是调控红树林生态效应的关键因素之一。壬二酸(Azelaic acid)是初次在红树植物中检测到的一种二元羧酸类根泌物,选用壬二酸和海洋原甲藻(Prorocentrum micans)为代表,以不同浓度壬二酸培养藻,在藻生长周期内定期观测其密度、形态、胞内甘油含量、色素含量等指标,进行室内红树植物根系分泌物对藻类的影响作用的初步的机理实验。主要结果如下:在低浓度0.5~1.5 mg/L时,壬二酸可作为营养物质被藻细胞所吸收。而在较高浓度2和4 mg/L时,壬二酸主要起化感抑制作用。细胞膜的脂质过氧化导致胞内甘油含量上升,色素体产生应激反应,色素合成量加大,特别是多甲藻黄素含量增加。通过细胞代谢产生更多的内含物质,如淀粉粒和脂肪,导致液泡增大。色素体是应激反应和抗逆作用的重要细胞器之一。由于壬二酸可以较低浓度出现较高的抑制效应,因此对红树林内的生态效应非以营养效应而以化感效应为主。红树植物根系分泌物对林内生态具有一定的调控作用,应加强野外条件下的红树植物多种根系分泌物的混合效应原位试验。

Effect of azelaic acid of mangrove root exudates on Prorocentrum micans

It is generally recognized that plant rhizosphere microbial biomass is higher than that of non-rhizosphere, and this is related to a variety of substances which secreted by plant roots. Different species of mangrove plant had different degree of eutrophication and with higher phytoplankton biomass, and this was estimated at least to be partly related with the mangrove plant root exudates (REs) and the control effect on the forest organisms. Mangrove plant root exudates are one of the key factors in modulating mangrove ecological effects. Azelaic acid is a kind of two carboxylic acids detected in mangrove plants root exudates for the first time. The preliminary indoor mechanism experiment of the effect of mangrove plant root exudates on algae was conducted by using azelaic acid and alga Prorocentrum micans, the alga was cultivated with different concentrations of azelaic acid. Algal density, shape, intracellular glycerol content, pigment content and other indexes were detected in the algal growth period. The main results are as follows: in low concentration of 0.5-1.5 mg/L, azelaic acid could be used as the nutrients to be absorbed by the algal cells. While at a higher concentration of 2 mg/L and 4 mg/L, azelaic acid mainly expressed as allelopathic inhibition. Cell membrane lipid peroxidation lead to intracellular glycerol content increased, Chromatoplast produced strong stress response, the pigment synthesis was increased, especially peridinin content. More intracellular substances produced through cell metabolisms, such as starch and lipid droplets, and resulting in enlargement of vacuoles. Chromatoplast is one of the most important organelle to response stress and to resist adversity. The ecological effect of azelaic acid was mainly classified to allelopathy as for its low concentration and higher inhibition effect. Mangrove plant root exudates has a regulatory role on forest ecology. In situ field test on the mixed effects of mangrove plant root exudates should be strengthened in the future.