熱逆境下植物生長促進細菌對萵苣發芽、 生理特性、營養成分和生長發育的影響

Abstract

全球暖化意指人類密集工業活動排放大量溫室氣體而導致地球大氣溫度升高之現象，是園藝產業所面臨的重要課題，而使用植物生長促進細菌(plant growth-promoting bacteria, PGPB)可作為減輕全球暖化對園藝作物生產沖擊的方式之一。本研究旨在探討PGPB對萵苣於熱逆境下生長之影響。本研究使用之菌種分離自2020年宜蘭縣三星鄉經歷異常熱浪後而存活下來之大蔥，且其共生潛力在進行中的研究已經得到驗證。依據各菌株之植物生長促進(plant growth-promotion, PGP)潛力，選出表現前五名的菌株(分別為Acinetobacter sp. GRB12、Bacillus sp. GFB04、Klebsiella sp. LFB06、Klebsiella sp. GRB10 及Klebsiella sp. GRB04)，並在後續的溫室試驗中，將其混合以對萵苣進行接種。本試驗共分為四種處理，分別為對照組、接種組、熱逆境組和熱逆境且接種組。在另外的生長箱試驗中則只選用Bacillus sp. GFB04及 Klebsiella sp. GRB10菌株進行單菌株接種，試驗共分為六種處理，分別為對照組、Bacillus sp. GFB04接種組、Klebsiella sp. GRB10接種組、熱逆境組和熱逆境且Bacillus sp. GFB04接種組和熱逆境且Klebsiella sp. GRB10接種組。兩個試驗均會分析植物之生理參數(葉綠素螢光及蒸騰作用)、生長參數(生物量)與植體營養成分(氮、磷、鉀、鈣、鎂及鐵)。結果顯示，熱逆境下的植物各項指標表現最差，接種PGPB的植物在熱逆境條件下比未接種的萵苣有更高的生物量及植體營養成分，且有更好的水分利用效率，接種組有更好的表現。由此可知，使用PGPB能增強萵苣耐熱性，有助於在未來高溫條件下進行萵苣之生產，並減少化學肥料的使用。

Climate change, especially global warming, is one of the global issues projected to threaten agriculture’s sustainability. To alleviate the impacts of global warming on horticultural crop production, especially cool-season crops, plant-growth-promoting bacteria (PGPB) was suggested. This study investigates the effects of selected PGPB on lettuce growth performance under heat-stress conditions. The bacteria’s plant growth-promoting potentials have been characterized and identified successfully in ongoing studies. Based on the in vitro plant growth-promoting potential evaluations, the top five bacteria were ranked and identified as Acinetobacter sp. GRB12, Bacillus sp. GFB04, Klebsiella sp. LFB06, Klebsiella sp. GRB10, and Klebsiella sp. GRB04. They were mixed to be an inoculum for inoculations on lettuce (Lactuca sativa L.) in the following in vivo experiment in temperature-controlled greenhouses. Another in-vivo chamber experiment was conducted by using Bacillus sp. GFB04 and Klebsiella sp. GFB10 as the single strain inoculum. The plants’ physiological traits (chlorophyll fluorescence and transpiration) and nutrient contents were measured at harvest, along with growth, development, and yield component analyses. The uninoculated plants under heat-stress condition showed the worst growth performance. In contrast, the plants with PGPB inoculation resulted in better plant growth under heat-stress conditions, as the uptake of nutrients was facilitated by the symbionts. Inoculation also improved lettuce’s photosystem II efficiency and decreased total water use under heat stress. In conclusion, the current study suggests that PGPB inoculation successfully enhances lettuce’s heat-tolerance. PGPB application could potentially help improve the sustainable production of lettuce with less fertilization under increasing temperatures.