Key Laboratory of Agro-Environment in the Tropics, Ministry of Agriculture, South China Agricultural University, Guangzhou 510642, China.
Guangdong Provincial Key Laboratory of Eco-Circular Agriculture, South China Agricultural University, Guangzhou 510642, China.
Molecules. 2022 Oct 15;27(20):6917. doi: 10.3390/molecules27206917.
Salicylic acid (SA) plays a critical role in allergic reactions of plants to pathogens and acquired systemic resistance. Thus far, although some research has been conducted on the direct effects of different concentrations of SA on the chemical defense response of treated plant parts (leaves) after at multiple post-treatments times, few research has reported on the systematic effects of non-treated parts (roots). Therefore, we examined direct and systemic effects of SA concentration and time following foliar application on chemical defense responses in maize variety 5422 with two fully expanded leaves. In the experiments, maize leaves were treated with different SA concentrations of 0.1, 0.5, 1.0, 2.5, 5.0 mM, and then, the presence of defense chemicals and enzymes in treated leaves and non-treated roots was measured at different time points of 3, 12, 24, 48, 72 h following SA foliar application. The results showed that direct and systemic effects of SA treatment to the leaf on chemical defense responses were related to SA concentration and time of measurement after spraying SA. In treated leaves, total phenolics content increased directly by 28.65% at the time point of 12 h following foliar application of 0.5 mM SA. DIMBOA (2,4-dihydroxy-7-methoxy-2H, 1, 4-benzoxazin-3 (4H)-one) content was directly enhanced by 80.56551.05% after 372 h following 0.55.0 mM SA treatments. Polyphenol oxidase and superoxide dismutase activities were directly enhanced after 1272 h following 0.55.0 mM SA treatments, whereas peroxidase and catalase activities were increased after 324 h following application of 1.05.0 mM SA. In non-treated roots, DIMBOA content and polyphenol oxidase activity were enhanced systematically after 348 h following 1.05.0 mM SA foliar treatments. Superoxide dismutase activities were enhanced after 324 h following 0.5~2.5 mM SA applications, but total phenolics content, peroxidase and catalase activity decreased in some particular concentrations or at the different times of measurement in the SA treatment. It can be concluded that SA foliar application at 1.0 and 2.5 mM produces strong chemical defense responses in maize, with the optimal induction time being 24 h following the foliar application.
水杨酸（SA）在植物对病原体的过敏反应和获得的系统抗性中起着关键作用。到目前为止，尽管已经有一些研究对不同浓度的 SA 对处理后的植物部分（叶片）的化学防御反应的直接影响进行了研究，但很少有研究报道非处理部分（根）的系统效应。因此，我们研究了叶面喷施 SA 后不同浓度和时间对玉米品种 5422 两片完全展开叶片的化学防御反应的直接和系统效应。在实验中，用 0.1、0.5、1.0、2.5、5.0mM 的不同 SA 浓度处理玉米叶片，然后在叶面喷施 SA 后 3、12、24、48、72h 测量处理叶片和非处理根中防御化学物质和酶的存在。结果表明，SA 处理叶片对化学防御反应的直接和系统效应与 SA 喷雾后测量的 SA 浓度和时间有关。在处理叶片中，0.5mM SA 叶面喷施 12h 时总酚含量直接增加 28.65%。DIMBOA（2,4-二羟基-7-甲氧基-2H，1,4-苯并恶嗪-3（4H）-酮）含量在 0.5-5.0mM SA 处理后 3-72h 内直接提高 80.56-551.05%。多酚氧化酶和超氧化物歧化酶活性在 0.5-5.0mM SA 处理后 12-72h 内直接增强，而过氧化物酶和过氧化氢酶活性在 1.0-5.0mM SA 处理后 3-24h 内增强。在未处理的根中，0.5-2.5mM SA 叶面处理后 3-48h 内 DIMBOA 含量和多酚氧化酶活性系统增强。超氧化物歧化酶活性在 0.5-2.5mM SA 处理后 3-24h 内增强，但在 SA 处理的某些特定浓度或不同测量时间，总酚含量、过氧化物酶和过氧化氢酶活性下降。综上所述，1.0 和 2.5mM 的 SA 叶面喷施在玉米中产生强烈的化学防御反应，最佳诱导时间为叶面喷施后 24h。
