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2009年10月31日

過氧化氫與植物的耐寒機制

    最近有則新聞在塔內食蟲板討論,筆者去追蹤了一下;因為筆者不是植物生理領域的人,所以原本並不清楚它的進展如何。許多看見新聞標題的朋友心中充滿了無限想像與期待,但實際上好像不是這麼一回事。為甚麼呢?請繼續看下去。

    下面是該研究團隊於2007年發表的論文摘要,關於過氧化氫與植物的耐寒機制:
Repetition of hydrogen peroxide treatment induces a chilling tolerance comparable to cold acclimation in mung bean.
Hung ShuHsienWang ChunChiIvanov, S VAlexieva, VYu ChihWen
Journal of the American Society for Horticultural Science, (2007) Vol.132(No.6)
Abstract

    Mung bean seedlings (Vigna radiata L.) of the cultivar Tainan No. 5 (a chilling-sensitive cultivar) pretreated with multiple sprays of 200 mM HO showed a tolerance to chilling at 4 degrees C for 36 h, measured by electrolyte leakage, that was greater than that induced by a single treatment and similar to that induced by cold-acclimation at 10 degrees C for 48 h. Two HO treatments at an interval of 3 h gave the optimum chilling tolerance. Tolerance induced by HO could be distinguished from that induced by acclimation at 10 degrees C according to length at 4 degrees C and corresponding electrolyte leakage. Chilling tolerance induced by HO depended on accumulation of glutathione (GSH), which could be significantly reversed by pretreatment with buthionine sulfoximine (BSO). In contrast, tolerance induced by incubation at 10 degrees C for 48 h in light was neither accompanied by accumulation of GSH nor reversed by BSO, suggesting that there are at least two independent mechanisms of developing chilling tolerance. Chilling tolerance of both cold-acclimated and HO-treated seedlings was decreased by ethyleneglycol-bis(aminoethylether)-N,N'-tetraacetic acid (EGTA) but not by ruthenium red, indicating that the influx of Ca²+ from extracellular, but not intracellular, pools is an important signal in the induction of tolerance. In confirmation, sprays of Ca²+ could be substituted for HO.

    筆者知道強迫各位去讀外文期刊是不人道的,不過說實在話,不去攝取新知就等著被淘汰吧!而且以為筆者會翻譯這篇摘要的朋友恐怕要讓你失望了,因為翻譯了你也應該用不上;但我會稍微說明一下這篇研究在做什麼。

    這個研究使用了200 mM 的過氧化氫(雙氧水)多次噴灑綠豆芽,然後發現它在特定環境下啓動了抗寒機制(註:以電解質流失情形來判斷,筆者推測可能跟正常生理機能維持有關)1-2天左右。先不去討論抗寒機制背後的問題,他的結論是來自細胞外的鈣離子是重要的逆境訊號,因此噴灑鈣離子可以取代過氧化氫,達到啓動抗寒機制的功能。

    各位看到這裡一定傻眼了,幫豬籠草噴灑鈣離子可以對抗逆境?這件事情大家想都沒想過,更不用說種植毛氈苔的朋友,一定想要翻桌:這種爛方法要怎麼用在毛氈苔上?(假設抗逆境機制包含高溫與低溫,雖然並沒有直接證據證明兩者的機制雷同。)

    首先要跟各位說:別太相信新聞的報導。再來針對應用的部份,筆者認為沒有那麼大的吸引力。雙氧水可能會對植物造成傷害,影響生長發育;而鈣離子的使用濃度並不確定,只知道讓細胞接觸鈣離子可以讓其忍受低溫。對其他不討厭鈣離子的植物,筆者認為這個方法用來暫時抵禦寒流可能有用;而對豬籠草來說,那就看各位有沒有那個膽子去做實驗了。

    原則上筆者認為對一些怕寒冷的豬籠草來說,在新芽處塗抹一些鈣離子含量較高的溶液是較合理的施用方式,相信對於植株不會有任何的損害。但由於筆者完全以室內簡易溫室栽培,目前並無打算進行測試。至於雙氧水,筆者相信這就是新聞報導中計畫主持人提到的”比較昂貴又會使植物生長停滯“的舊抗寒液配方,因此不鼓勵各位施用。如果有心對這個議題深入研究的朋友可以自行閱讀相關文獻。

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