施硅对感染白粉病小麦叶片抗病相关酶活性及硅微域分布的影响

ACTIVITIES OF DEFENCE-RELATED ENZYMES AND MICRO-REGIONAL DISTRIBUTION OF SILICON IN LEAVES OF POWDERY MILDEW-INFECTED WHEAT AS AFFECTED BY EXTRANEOUS SILICON

以抗/感白粉病的南农99-18/苏麦3号为试验材料,研究外源硅对接种白粉病后小麦叶片的几丁质酶、β-1,3葡聚糖酶、苯丙氨酸解氨酶(PAL)、多酚氧化酶(PPO)活性和叶片硅微域分布的影响,以探讨外源硅增强小麦抗白粉病的作用机理。结果表明,在不接病原菌时,施硅与否对抗/感病品种的PAL、PPO、β-1,3葡聚糖酶活性和感病品种的几丁质酶活性无显著性影响,但施硅可显著地提高抗病品种的几丁质酶活性;接种病原菌后,抗/感品种小麦叶片的几丁质酶、β-1,3葡聚糖酶、PAL和PPO活性均显著提高,而施硅处理显著地提高了感病品种的这四种酶活性和抗病品种的几丁质酶与β-1,3葡聚糖酶活性,但施硅处理对于抗病品种的PAL和PPO活性影响不显著。同时,施硅处理下,叶片硅元素相对重量都有不同程度提高,并有向刺状体基部和维管束组织富集趋势;接种病原菌后,叶片硅元素明显向病原菌侵染位点聚集,尤其有外源硅供给条件下,这种富集效应尤为显著。这意味着,硅不仅通过调节植株体内与抗病性密切相关的酶活性,而且同时可通过在侵染位点的淀积而构建了防病原菌侵入的"物理或机械屏障",以达到增强小麦的抗病性,从而抑制小麦白粉病病害发展。

An experiment was conducted using a resistant eultivar of wheat （ Triticum aestivum L. Nannong 99-18） and a susceptible cultivar wheat （ Sumai No. 3） to investigate effects of silicon （Si） on activities of defense-related enzymes （chitinase, β-1,3-glucanase, phenylalanine ammonia-lyase （PAL） and polyphenoloxidase （PPO）） and micro-regional distribution of silicon in leaves infected by powdery mildew （Blurneriae graminis f. sp. Tritici）. When wheat plants were not inoculated with powdery mildew, application of Si did not have much effect on activities of β-1,3-glucanase, PAL and PPO in both wheat cultivars or on activities of chitinase in the susceptible wheat cultivar, however, Si application was found to increase the activity of chitinase in the resistant wheat cultivar. Moreover, the activities of chitinase, β-1,3- glucanase,PAL and PPO increased significantly in both wheat cultivars after infection of powdery mildew. Except for the activities of PAL and PPO in the resistant wheat cultivar, all enzyme activities were significantly higher in Si-treated plants than in non-Si-treated plants after wheat plants were infected by powdery mildew. In addition, regardless of inoculation and Si addition, Si was mainly concentrated in trichomes and vascular bundle tissues. However, the relative content of Si markedly increased in leaf tissues, and Si rapidly accumulated at infected sites when plants were infected by powdery mildew, especially in plants treated with Si. These findings suggest that Si enhances wheat resistance to powdery mildew not only by promoting expression and activities of defense-related enzymes, but also by building up physical barriers against pathogens through Si accumulation in plants infected by powdery mildew.