Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal Pietermaritzburg, Scottsville 3209, South Africa.
Laboratory of Growth Regulators, Czech Academy of Sciences, Institute of Experimental Botany, and Palacký University, Faculty of Science, CZ-78371 Olomouc, Czech Republic.
Plant Physiol. 2019 Oct;181(2):458-470. doi: 10.1104/pp.19.00575. Epub 2019 Aug 14.
The biologically active molecules karrikinolide (KAR) and trimethylbutenolide (TMB) present in wildfire smoke play a key role in regulating seed germination of many plant species. To elucidate the physiological mechanism by which smoke-water (SW), KAR, and TMB regulate seed germination in photosensitive 'Grand Rapids' lettuce (), we investigated levels of the dormancy-inducing hormone abscisic acid (ABA), three auxin catabolites, and cytokinins (26 isoprenoid and four aromatic) in response to these compounds. Activity of the hydrolytic enzymes α-amylase and lipase along with stored food reserves (lipids, carbohydrate, starch, and protein) were also assessed. The smoke compounds precisely regulated ABA and hydrolytic enzymes under all light conditions. ABA levels under red (R) light were not significantly different in seeds treated with TMB or water. However, TMB-treated seeds showed significantly inhibited germination (33%) compared with water controls (100%). KAR significantly enhanced total isoprenoid cytokinins under dark conditions in comparison with other treatments; however, there was no significant effect under R light. Enhanced levels of indole-3-aspartic acid (an indicator of high indole-3-acetic acid accumulation, which inhibits lettuce seed germination) and absence of trans-zeatin and trans-zeatin riboside (the most active cytokinins) in TMB-treated seeds might be responsible for reduced germination under R light. Our results demonstrate that SW and KAR significantly promote lettuce seed germination by reducing levels of ABA and enhancing the activity of hydrolytic enzymes, which aids in mobilizing stored reserves. However, TMB inhibits germination by enhancing ABA levels and reducing the activity of hydrolytic enzymes.
野火烟雾中存在的生物活性分子贝壳杉烯内酯 (KAR) 和三甲基丁烯内酯 (TMB) 在调节许多植物物种的种子萌发中起着关键作用。为了阐明烟雾水 (SW)、KAR 和 TMB 通过调节感光型“大急流城”生菜 () 种子萌发的生理机制，我们研究了休眠诱导激素脱落酸 (ABA)、三种生长素分解代谢物和细胞分裂素 (26 异戊烯基和 4 种芳香族) 的水平，以响应这些化合物。还评估了水解酶α-淀粉酶和脂肪酶的活性以及储存的食物储备（脂质、碳水化合物、淀粉和蛋白质）。这些烟雾化合物在所有光照条件下都能精确调节 ABA 和水解酶。在 TMB 或水处理的种子中，红光 (R) 下的 ABA 水平没有明显差异。然而，与水对照相比，TMB 处理的种子发芽率显著受到抑制（33%）。与其他处理相比，KAR 在黑暗条件下显著增强了总异戊烯细胞分裂素；然而，在 R 光下没有显著影响。TMB 处理的种子中吲哚-3-天冬氨酸（高吲哚-3-乙酸积累的指示剂，抑制生菜种子萌发）水平升高，而反式玉米素和反式玉米素核苷（最活跃的细胞分裂素）不存在，这可能是导致 R 光下发芽率降低的原因。我们的结果表明，SW 和 KAR 通过降低 ABA 水平和增强水解酶活性来显著促进生菜种子萌发，从而有助于动员储存的储备。然而，TMB 通过提高 ABA 水平和降低水解酶活性来抑制发芽。
