Blast, caused by Pyricularia oryzae , is one of the most important diseases affecting rice yield worldwide. This study investigated the potential of silicon (Si) to counteract the effect of picolinic acid (PA), a non-host selective toxin produced by P. oryzae , on the photosynthetic performance, on the activities of defense enzymes, and the antioxidative metabolism of rice plants. Plants were grown in nutrient solution containing 0 or 2 mM of Si and non-sprayed or sprayed with PA (0.5 mg PA/ml; 20 ml per plant) at 35 days after emergence. The PA-sprayed plants exhibited necrotic lesions on leaves that resembled those caused by P. oryzae infection. In the presence of Si, the necrotic lesions on the leaves of PA-sprayed plants were less in number and of reduced size. The necrosis of leaf tissues caused by PA spray was accompanied by lower values of net CO 2 assimilation rate and transpiration rate and high internal CO 2 concentration values indicating the occurrence of biochemical limitations in photosynthesis regardless of Si supply. For plants non-sprayed with PA, there was no change in the activities of the enzymes involved in host defense (chitinases (CHI), β -1,3-glucanases (GLU), polyphenoloxidases (PPO), and phenylalanine ammonia-lyases (PAL)) and on the antioxidative system (superoxide dismutases (SOD), catalases (CAT), peroxidases (POX), ascorbate peroxidases (APX), and glutathione reductases (GR)). The activities of CHI, GLU, PAL, GR, POX, and SOD were greater on the leaves of PA-sprayed plants in the absence of Si than on its presence. Silicion did not alleviate the physiological and biochemical aspects of PA-mediated stress on rice leaf blades. We hypothesize that Si forms a physical barrier. Such physical impediment makes the diffusion of PA into the leaf blades more difficult rather than actively affecting the physiology and biochemistry of the plant.

中文翻译：

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硅不能减轻施加在水稻叶片上的吡啶甲酸胁迫

稻瘟病是由稻瘟病菌引起的稻瘟病，是世界范围内影响水稻产量的最重要病害之一。本研究调查了硅 (Si) 抵消吡啶甲酸 (PA)（一种由稻瘟病菌产生的非寄主选择性毒素）对光合性能、防御酶活性和抗氧化代谢影响的潜力。水稻植物。在出苗后 35 天，植物在含有 0 或 2 mM Si 的营养液中生长，并且不喷洒或喷洒 PA（0.5 mg PA/ml；每株植物 20 ml）。喷洒 PA 的植物在叶子上表现出坏死病变，类似于由稻瘟病菌感染引起的病变。在 Si 存在下，喷洒 PA 的植物叶片上的坏死病灶数量较少且尺寸减小。由 PA 喷雾引起的叶组织坏死伴随着较低的净 CO 2 同化率和蒸腾率值以及较高的内部 CO 2 浓度值，表明光合作用中的生化限制的发生与 Si 供应无关。对于未喷洒 PA 的植物，参与宿主防御的酶（几丁质酶 (CHI)、β -1,3-葡聚糖酶 (GLU)、多酚氧化酶 (PPO) 和苯丙氨酸解氨酶）的活性没有变化。 PAL)) 和抗氧化系统（超氧化物歧化酶 (SOD)、过氧化氢酶 (CAT)、过氧化物酶 (POX)、抗坏血酸过氧化物酶 (APX) 和谷胱甘肽还原酶 (GR)）。在没有 Si 的情况下，喷洒 PA 的植物叶片上的 CHI、GLU、PAL、GR、POX 和 SOD 的活性高于存在 Si 时的活性。硅并没有减轻 PA 介导的水稻叶片胁迫的生理和生化方面。我们假设 Si 形成了物理屏障。这种物理障碍使 PA 扩散到叶片中变得更加困难，而不是积极影响植物的生理和生物化学。