根溫降低與植物生長促進細菌在熱逆境下對萵苣生長的影響

Abstract

根據政府間氣候變化專門委員會(Intergovernmental Panel on Climate Change, IPCC)的調查報告，全球地表溫度至2100年預計上升2到5°C，而溫度的上升將影響萵苣的生產。萵苣為全球重要的經濟作物，使用以下兩種方法評估是否能於未來較高溫度的環境下維持萵苣生產：根部溫度(root zone temperature, RZT)降低與施用由宜蘭三星蔥分離出的植物生長促進細菌 (plant growth-promoting bacteria, PGPB) ― 枯草桿菌(Bacillus subtilis GFB04). 在前三個試驗中，根溫隨環境變動(RZT-A)與根溫維持低溫(RZT-CO)兩種根溫處理，和高空氣溫度(H-Tair 35/30°C)與低空氣溫度(L-Tair 30/25 或25/20 °C)兩種氣溫處理。在第四個試驗中，根溫和接種枯草桿菌與否則為兩個主要因子。結果顯示，RZT-CO比RZT-A顯著增加了萵苣的地上部鮮重47%至53%，同時地上部的相對含水量(RWC)增加，而根部鮮重降低乾重卻升高，係因根部RWC於RZT-CO組顯著降低，這可能與根部活力有關。在試驗中，葉片的生理表現沒有呈現一致的趨勢，然葉片溫度與環境溫度差(Tdif) 隨萵苣生長而整體降低，可能與萵苣整體對於環境的適應力提升相關。接種枯草桿菌在高溫下減少植物的鮮重和氣孔導度，同時顯著增加丙二醛(malondialdehyde, MDA)的含量，顯示接種之後的萵苣相比於未接種的萵苣，於高溫下面臨更強的逆境。或許此菌株與本奶油萵苣品種於水耕環境下並不相容，未來若想於水耕環境中施用PGPB可能需要尋找其他菌株方可有其他發現。

According to IPCC (Intergovernmental Panel on Climate Change), the global surface temperature is expected to increase by 2°C to 5°C by 2100, which could impact the production of lettuce, an important vegetable worldwide. Two approaches were evaluated to maintain or increase lettuce production under heat stress: cooling the root zone temperature (RZT) and applying Bacillus subtilis GFB04, one of the plant growth-promoting bacteria (PGPB) isolated from Welsh onion. Ambient RZT (RZT-A) compared to RZT cooling (RZT-CO), and high air temperature (H-Tair, 35/30°C) compared to low air temperature (L-Tair, 30/25 or 25/20) were the main two factors in the first three experiments (Expts.). In Expt. 4, RZT and inoculation (LB compared to Inoc.) were investigated. The results indicated that RZT-CO significantly increased lettuce shoot fresh weight (FW) by 47% to 53% under H-Tair. The relative water content (RWC) of the shoot increased under RZT-CO, but root RWC was reduced under RZT-CO, which might relate to the root vigor. The leaf physiological performance did not exhibit a consistent trend in the Expts. The B. subtilis strain did not appear compatible with butterhead lettuce in a hydroponic system, as it decreased plant FW and gs and increased the malondialdehyde contents under H-Tair.