三种酚酸类化合物对莴苣幼苗的化感作用及机理初探

Allelopathic effect and mechanism of action of three phenolic acids on lettuce seedlings

化感物质通过植物体释放到农田土壤中,可对作物生长造成严重影响。酚酸是一类重要的化感物质,由于其相对分子质量小,结构稳定,因而不易降解而累积在土壤中,进而影响作物生长,是引起连作障碍问题的一类主要化合物。为了明确酚酸类物质对植物生长影响的途径,探讨其化感作用机理,以3种结构相似的化合物——苯甲酸、水杨酸和对羟基苯甲酸为研究对象,以莴苣幼苗为活性受体,通过测定化合物对莴苣幼苗根、茎生长的影响,评价了其对植物的毒活性;并借助于荧光显微镜,通过FDA/PI双染色法和DHE染色法,分别研究了3种酚酸类化合物对受体植物根尖细胞活力和活性氧积累的影响。结果表明:3种酚酸类化合物对莴苣幼苗根、茎的生长均表现出低浓度促进、高浓度抑制的作用模式;莴苣幼苗在高浓度酚酸的胁迫下,其体内活性氧大量积累,高浓度的活性氧对莴苣幼苗细胞膜结构等具有显著的破坏作用,进而导致细胞活力降低甚至凋亡,最终抑制植物生长。

Allelochemicals are released into the farmland soils by plants, which will affect the growth of other plants. Phenolic acids are one kind of important allelochemicals. Due to their small molecular weight and stable structure, phenolic acids are hardly decomposed in nature. Thus they would accumulate in the soil, and affect the crop production during a long period of time. In fact, phenolic acids are the main compounds causing the problem of continuous cropping obstacle. In order to evaluate the allelopathic effect and study the mechanism of action of phenolic acids, the allelopathic effects of benzoic acid, salicylic acid and 4-hydroxybenzoic acid were assayed using lettuce as the receptor. In addition, the influence on the cell viability and reactive oxygen species （ROS） accumulation of lettuce roots by the phenolic acids were studied with FDA/PI double staining and DHE staining, respectively. The results showed that the phenolic acids promoted the root and shoot elongation at low concentrations, and exhibited inhibitory effects at high concentrations. Moreover, under high concentrations, the above three allelochemicals could induce the accumulation of ROS. High concentrations of ROS might cause membrane structural damage and then influenc the cell viability, which will ultimately result in the growth inhibition of lettuce seedlings.