硅诱导黄瓜抗炭疽病的作用机理研究

Both sandy and hydroponic culture experiments were conducted in this paper to investigate the effects of soluble silicon and inoculation with Colletotrichum lagenarium and Sphaerotheca fuliginea on resistance against anthracnose and powdery mildew as well as the mechanism of induced resistance by using microscopic and enzymatic methodologies. The main results were presented as follows:.The leaf peroxides (POD) activities in plants inoculated with Colletotrichum lagenarium were significantly higher than those without inoculation, while no significant difference was observed in POD activity between Si-deprived and Si-supplied plants. Difference of POD activity in cucumber leaves between inoculated and un-inoculated plants decreased with increased leaf position upward from the inoculated leaf. The leaf POD activity induced by Colletotrichum lagenarium was highest on the 8th day and began to drop about two weeks after inoculation. Similarly, inoculation with Colletotrichum lagenarium increased polyphenoloxidase(PPO)、phenylalanine ammonia-lyase (PAL) activity and lignin content, while silicate treatment failed to significantly enhance PPO、PAL activity and lignin content. The cucumber plants inoculated with Colletotrichum lagenarium had significantly lower disease index with relative immunization efficiency of 33.2% compared to those without inoculation, while no significant difference was observed in disease index between Si-deprived and Si-supplied plants. .The POD、PPO and chitinase activities of leaves in plants supplied with Si and infected by Sphaerotheca fuliginea were significantly higher than those infected only without Si supplied and the control, respectively. Silicate added failed to significantly enhance the leaf POD、PPO and chitinase activities in plants un-inoculated with Sphaerotheca fuliginea. Effect of silicate and inoculation on activities of enzymes in the inoculated leaf was higher than in the un-inoculated one. The effect of Si on activities of enzymes and resistance against powdery mildew was the most significant in the hydroponics system containing 1.7 mmolL-1 Si. The leaf POD activity induced by Sphaerotheca fuliginea had two peaks and was highest on the 8th day and the 16th day after inoculation, respectively. The POD activity for the Si-treated leaves of cucumber inoculated with Sphaerotheca fuliginea was higher than that of the leaves inoculated only. When cucumber plants were infected by Sphaerotheca fuliginea, the activity of superoxide dismutase (SOD) decreased in resistant cucumber cultivar and increased in susceptible cucumber cultivar, whereas that of plants supplied with Si was significantly lower than in Si-deprived plants. The leaf PAL activity in plants infected was significantly higher than in plants un-infected. Silicon increased the PAL activity of the leaf inoculated and decreased that of the leaf un-inoculated. The cucumber plants inoculated with Sphaerotheca fuliginea did not lower the disease index, while Si added significantly decreased the disease index. Silicon and calcium was concentrated on the base of the trichomes in the surface of the epidermis. In different tissues of cucumber leaves, the content of silicon was higher in the upper epidermis and lower epidermis, and the content of calcium was even and lower. There wasn't any relationship between distribution of silicon and penetration sites of fungal hyphae. In the regions where Si was heavily deposited, fungal hyphae penetrated the epidermis of leaf through gaps of cell, while fungal hyphae and penetration sites were almost free from any specific silicon accumulation. After the Si-treated plants were infected by Sphaerotheca fuliginea, the content of silicon in the mesophyllous cells increased. After the leaf of cucumber plants was infected by Sphaerotheca fuliginea, calcium in the epidermal was more evenly distributed and not concentrated only at the base of the trichomes, regardless of Si supply. The content of calcium in the upper epidermis of Si-supplied cucumber leaves was significantly higher than that of Si

彩盆栽法应用能谱仪、原子力显微镜研究硅在感炭疽病的黄瓜叶片细胞壁、真菌侵染部位的微域分布，揭示质外体无定形硅向晶体硅的转化过程及其细胞间层钙的聚合过程；采用酶学和细胞显微化学技术探讨硅对染病黄瓜叶片中与抗病有关的几种酶和代谢物的影响，揭示硅提高黄瓜抗病性的机理。对于理解硅的生物学功能、寻找抗病新途径具有重要意义。