細菌釋放之揮發性有機化合物對水稻與阿拉伯芥於缺氮與缺鐵環境下生長之促進效應

Abstract

長期過度施用化學施肥會破壞土壤化學與物理性質，導致土壤酸化與土壤鹽鹼化，嚴重影響作物生長與產量。因此，尋求環境友善且有益植物生長的生物肥料成為永續農業重要課題之一。植物生長促進細菌已廣泛應用於作物生產，除了直接施用，亦有研究顯示植物生長促進細菌釋放之揮發性有機化合物 (volatile organic compounds, VOC) 也能提升植物生長勢。目前不清楚養分的存無對促生效益的影響，對植物的訊號接收與下游的傳遞機制了解也有限，因此本研究欲探討氮和鐵影響Bacillus sp. Pp16和Pp20釋放之VOC對於水稻與阿拉伯芥幼苗生長促進效益之差異。比較在氮源充足和缺乏的環境中，水稻處理Pp16和Pp20釋放之VOC後，僅在缺氮的條件下可觀察到生長促進效果，轉錄體分析顯示缺氮下Pp16 VOC處理可能透過提升水稻光合作用與防禦反應促進水稻生長，而在缺鐵環境下，VOC處理沒有明顯的影響；在養分充足的條件下阿拉伯芥接受VOC處理顯著提升生長勢，缺氮或缺鐵則降低促進效果，且抑制生長素運輸降低VOC處理在缺鐵下對根長的影響，說明VOC處理可能透過調控生長素來改變阿拉伯芥的根系結構。綜合上述， Pp16和Pp20釋放之VOC對植物生長的促進效果受到養分和物種的影響，未來將持續探討VOC對於植物養分吸收效率、同化、分布之影響，及背後的調控機制。

Long-term overfertilization negatively influence soil chemical and physical properties, leading to soil acidity and salinity. In addition to judicious use of fertilizer, the environmentally friendly strategies are required to promote sustainable agriculture. The application of plant growth-promoting bacteria (PGPB) has become widely adopted in agriculture. In addition to direct application, volatile organic compounds (VOC) released by PGPB have been shown to enhance plant growth. The influence of nutrient availability on the growth-promoting effects of VOC treatment remains unclear, and our understanding of VOC perception and downstream signaling in the associated plants is still limited. Therefore, this study aimed to investigate how nitrogen and iron availability affect the growth-promoting effects of VOC released by Bacillus sp. Pp16 and Pp20 on rice (Oryza sativa) and Arabidopsis (Arabidopsis thaliana) seedlings. In rice, VOC-mediated growth promotion was only observed under nitrogen-deficient conditions. The results of transcriptomic analysis showed that, under nitrogen-limited conditions, Pp 16 VOC treatment promotes rice growth by enhancing photosynthetic capacity and activating defense responses. In contrast, plant growth was not affected by VOC treatment under iron-deficient conditions. In Arabidopsis, the growth promotion mediated by bacterial VOC was able to be observed under nutrient-sufficient conditions, whereas nitrogen or iron deficiency reduced the growth-promoting effects. Furthermore, the inhibition of auxin transport attenuated the VOC-induced enhancement of root length under iron-deficient conditions, suggesting that VOC may modulate root architecture in Arabidopsis partially through the regulation of auxin transport. Taken together, these findings demonstrated that the growth-promoting effects of VOC released by Pp16 and Pp20 were influenced by both nutrient availability and plant species. Future research will focus on elucidating the roles of VOC in regulating plant nutrient uptake efficiency, assimilation, and distribution, as well as the underlying molecular mechanisms involved.