水楊酸對日日春[Catharanthus roseus（L.）G. Don]在淹水逆境下生長與生理反應之影響

Effects of Salicylic Acid on the Growth and Physiology Response of Periwinkle [Catharanthus roseus (L.) G. Don] under Waterlogging Stress

日日春為臺灣常見之觀賞草本花卉，但其根系不耐潮濕，長時間淹水會影響植株觀賞品質甚至死亡，影響栽培和商業生產。水楊酸（salicylic acid，SA）是一種植物逆境荷爾蒙，其作為訊號分子在誘導植物體內和非生物逆境耐受機制上發揮至關重要的作用。本研究以日日春重瓣品種‘幸運’、‘火焰’與單瓣品種‘Heatwave’作為參試材料，以葉面噴施0.25、0.5或1 mM SA後，經二次藥劑噴施再進行淹水至介質表面處理8天，隨後恢復正常環境4天，發現日日春植株出現葉片黃化、萎凋等外觀變化，株高、葉面積、鮮乾重、葉綠素計讀值顯著下降，並且光合參數、葉綠素螢光之測值降低，同時離子滲漏率和丙二醛含量也增加。施用0.5 mM SA能夠顯著改善日日春在淹水逆境下的植株生長性狀，並且在淨光合速率、Fv／Fm值等生理指標也有顯著的改善效果，因此以噴施0.5 mM SA為最佳之處理。此結果可作為未來日日春栽培管理與提升逆境耐受機制的研究基礎。

Catharanthus roseus (L.) G. Don (periwinkle) is a widely cultivated ornamental flower in Taiwan. However, its root system is sensitive to waterlogging, and long period of flooding can cause damage to the plant or even plant death, resulting commercial production loss. Salicylic acid (SA) is a plant hormone that functions as a signaling molecule, playing a critical role in activating biochemical pathways related to plant tolerance against abiotic stresses. In this study, three periwinkle cultivars were used, including the double-flowered‘Lucky’and‘Flame’, and the single-flowered‘Heatwave’. Plants were treated with three different concentrations of SA (0.25, 0.5, or 1 mM) through foliar spray. On the next day after the second application of SA, plants were subjected to flooding stress for 8 days, followed by a 4-day recovery under regular conditions. Flooding caused leaf yellowing and wilting of periwinkle plants with significant decline in various growth parameters including plant height, leaf area, fresh and dry weight, and SPAD value. In addition, photosynthetic parameters and Fv/Fm values declined, while electrolyte leakage and malondialdehyde (MDA) content increased. Among the SA treatments, application of 0.5 mM SA most effectively improved plant growth under flooding stress, with significant enhancements in net photosynthetic rate and Fv/Fm values. Therefore, spraying 0.5 mM SA was the best treatment. The results provide a foundation for future research on the cultivation management and strategies to enhance its flooding tolerance of periwinkle.