Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/36748
標題: 浸水逆境下玉米幼苗植株過氧化作用與抗氧化系統的反應
Responses of Peroxidation and Antioxidative Systems in Corn(Zea mays L.) Seedling During Waterlogging Stress
作者: 張文東
Chang, Wen-Dong
關鍵字: Corn;玉米;Waterlogging Stress;Peroxidation;Antioxidative Systems;Plant Growth Regulators;Polyamines;Active Oxygen Species Scavengers;浸水逆境;過氧化作用;抗氧化系統;植物生長調節素;多元胺;活性氧族清除劑
出版社: 農藝學系
摘要: 
本論文主要目的在探討玉米遭遇浸水逆境時,植株過氧化作用和抗氧化系統的反應。試驗採砂耕盆栽植株於溫室進行。首先以台灣目前推廣的單雜交種飼料玉米(台農1號、台農351號和台南17號)及青割玉米(台南19號)三葉期幼苗進行浸水試驗,根據植株生長和乾物重的反應,以台農系列受抑制的程度較台南系列小,而且植株脂質過氧化作用的產物丙二醛(malondialdehyde, MDA)含量亦以單雜交種玉米台南19號(以下簡稱台南19號)增加最多。因此,選擇台南19號做為進一步浸水傷害反應的研究對象。
台南19號玉米幼苗進行十天的浸水處理,結果顯示植株生長受阻,乾物重減少,同時葉片葉綠素和蛋白質含量皆降低。分析植株過氧化作用,顯示隨著浸水日數的延長,植株體內超氧自由基產生速率和過氧化氫含量亦呈現增加,同時植株遭受過氧化傷害(即MDA含量增加)的程度亦愈加劇。進一步測定抗氧化系統的反應,結果顯示酵素性抗氧化物,除了根部glutathione reductase(GR)活性表現增加外,隨著浸水日數延長,葉片superoxide dismutase(SOD) 、ascorbate peroxidase(AP) 和GR活性,以及根部SOD和AP活性皆減少。至於非酵素性抗氧化物的表現,台南19號幼苗於浸水期間,葉片和根部ascorbate含量皆呈現增加趨勢;植株glutathione含量以還原態(reduced form glutathione, GSH)為主,葉片GSH含量在浸水初期明顯增加,而根部GSH含量則是在浸水後期表現增加。顯然地,浸水處理導致玉米植株抗氧化系統防禦能力的改變,這種改變可能涉及到植株的過氧化傷害。
從台南19號幼苗過氧化作用和抗氧化系統反應的特性中,亦顯示在浸水處理下,植株葉齡愈大者表現愈嚴重的過氧化傷害。雖然老葉抗氧化系統最先發生反應,但是老葉的防禦系統也是最先表現衰退。至於根系的表現,在浸水處理下,台南19號幼苗不定根的過氧化作用較種子根來得大,而種子根和不定根內非酵素性抗氧化物,於浸水初期二者的ascorbate和glutathione含量皆表現相近,但浸水後期種子根內glutathione含量明顯較不定根減少。浸水逆境下不定根內酵素性抗氧化物AP和GR活性較種子根增加,但SOD活性則無差異。因此,浸水逆境下的台南19號植株過氧化作用和抗氧化系統反應,因部位和株齡而有不同程度的表現,幼葉過氧化傷害較老葉表現輕,不定根耐淹能力較種子根佳。
解決作物淹水傷害的方法,即是在最短的時間內進行排水處理,讓植株儘速恢復其生長。試驗結果顯示,排水處理五天可以恢復台南19號植株的生長,其中以根部恢復的程度較大。排水處理亦明顯減輕台南19號幼苗因浸水引起的過氧化作用,並且沒有淹水後傷害(post-flooding injury)的發生;而排水處理後植株過氧化作用的降低,可能是因為AP和GR活性的恢復,使抗氧化防禦能力增加。
除了利用排水方式以解決淹水造成作物的傷害和減產外,試驗亦考慮以植物生長調節素,包括IAA、GA3、BA、ABA、ethephon和多元胺,以及活性氧族清除劑等,期利用外加處理可以減輕台南19號幼苗的浸水傷害,增加植株的抗氧化防禦能力。試驗結果顯示以前處理(pretreatment)方式較浸水同時噴施處理成效大,能夠減輕台南19號植株浸水傷害和降低脂質過氧化作用。在外加植物生長調節素處理的表現方面,以外加BA處理得到的效果較佳,可以減輕浸水傷害,降低植株過氧化作用。不過,外加ABA處理反而促進浸水傷害,導致植株過氧化作用更為嚴重。然而外加BA和ABA處理皆可增加台南19號植株浸水逆境抗氧化系統的防禦能力,尤其是增加glutathione的含量。顯然ABA處理所增加glutathione含量不足以清除自由基所產生的過氧化作用傷害,導致防禦系統作用不完全,無法有效降低脂質過氧化作用。外加多元胺處理,以putrescine(Put)處理略有減輕浸水傷害的效果,但是這種恢復效果似乎與增加抗氧化系統防禦能力的關係不大。
另外,在外加活性氧族清除劑處理方面,以ascorbate(AsA)和GSH外加處理對恢復植株生長及增加乾物重的效果較佳,但是兩者的作用可能並非透過減輕浸水植株的脂質過氧化作用,來達成其恢復的作用。
此外,台南19號在排水處理的試驗中同時噴施BA、ABA、Put、AsA和GSH的外加處理,並無法在短時間內有效加速排水植株的恢復作用,減輕過氧化傷害,甚至噴施ABA反而加重排水植株發生過氧化傷害,其原因可能是由於減少glutathione含量,降低防禦過氧化作用的能力。因此,就本試驗所使用藥劑而言,外加處理對增加排水植株的恢復效果並不顯著。
綜合上述結果顯示,台南19號幼苗在浸水處理下,植株體內大量活性氧族被誘導產生,導致脂質過氧化作用發生的機率大增,再加上植株體內抗氧化酵素活性的降低和非酵素性抗氧化物含量發生改變,使得浸水植株本身的抗氧化防禦能力降低,脂質過氧化傷害更形嚴重。在尋求減輕台南19號植株浸水傷害的途徑之中,以直接進行排水處理是最經濟而有效的方式;在台南19號植株遭遇浸水逆境之前,若以BA、AsA和GSH外加處理,亦可以得到減輕浸水傷害的成效,減輕傷害的效果似乎與植株體內抗氧化系統有某些程度的關連,尤其是以ascorbate-glutathione系統中的glutathione變化,可能扮演重要的防禦和解毒作用。至於在台南19號幼苗遭遇浸水逆境同時噴施植物生長調節素或活性氧族清除劑,其減輕浸水傷害的成效不如前處理的效果來的好;而排水處理同時噴施此等藥劑處理,對排水植株的恢復無加成的作用。

The purpose of this study is to explore the responses of peroxidation and antioxidative systems of corn seedling under the waterlogging stress. In order to select the proper cultivar as the experimental material, pot-grown V3 seedlings of four corn cultivars (Tainung 1, Tainung 351, Tainan 17, and Tainan 19) were subjected to waterlogging treatment. It showed that Tainan 19 was the most susceptible to waterlogging and thus used as experimental material for further studies.
During 10 days waterlogging period, corn seedling of Tainan 19 showed a decrease in growth, dry weight, the content of chlorophyll and soluble protein. Waterlogging treatment resulted in increase of superoxide anion generation, H2O2 production, and MDA content in corn plants. The enzymatic antioxidants (SOD, AP and GR) of both leaves and roots of waterlogging seedling were reduced except GR activity in root. In nonenzymatic antioxidants, waterlogging increased the content of ascorbate of corn seedling. The reduced form of glutathione (GSH), an increase was also found in both leaves and root of waterlogging seedling, however, the time of increase in the leaves was earlier than that in roots.
Responses of peroxidation and antioxidative systems in corn seedlings of Tainan 19 on waterlogging treatment were increased by age of leaves. Although the antioxidative systems in the older leaves were enhanced earlier than that of the younger, the reduction of defense systems in the older leaves were faster than that of the younger. Peroxidative injury in adventitious root was much greater than that in seminal root under waterlogging treatment. Ascorbate and glutathione contents in both seminal and adventitious roots showed similarity at the early stage of the experiment, but glutathione content of seminal root was significantly reduced than that of adventitious root. The activities of AP and GR in adventitious root were higher than that of seminal root during this experiment, but SOD activity was not different in both roots. Apparently, these results indicated that waterlogging induced damage of peroxidation and antioxidative systems, depend on different tissue and plant age of corn seedling.
Draining is one of the most effective way to alleviate injury and recover growth from waterlogging. In the drainage experiment, corn seedling of Tainan 19 was recovered, especially in root. Peroxidation was also significantly decreased in drained corn seedling and there was not appearance of post-flooding injury. Decrease in peroxidation of drained plant was assumed due to increased in antioxidative defense capacities by enhanced activities of AP and GR.
In addition to draining, application of plant growth regulators, polyamines and active oxygen species scavengers were expected to eliminate waterlogged damage of corn seedling and enhanced antioxidative defense capacities. The results indicated pretreatment with various chemical agents was more effective than that of treatments with waterlogging simultaneously. Among plant growth regulators, the effect of BA treatment was the greatest and significantly reduced injury and peroxidation of waterlogged corn plants. ABA treatment enhanced serious injury and peroxidation. However, antioxidative defense mechanisms were promoted in both application of BA and ABA, especially increase of glutathione content. It was suggested that increasing glutathione content in plant by ABA applied could not scavenged the production of excessive active oxygen species, and lead to increased damage of peroxidation. In the exogenous polyamines treatments, there was no direct evidence for the relationship between recovery effects and antioxidative systems, although the waterlogging injury of corn seedling were slightly reduced.
In the exogenous active oxygen species scavengers treatment, the effects of AsA and GSH on recovery of plant growth and dry weight accumulation were greater than others. The recovery mechanism of the two agents might not due to reduction of plant peroxidation.
Under post-waterlogging, treatment of BA, ABA, Put, AsA and GSH sprayed simultaneously to Tainan 19 corn seedling. These exogenous agents were not shown an additional effect on the recovery plant by draining. Application of ABA on the drained plant was even increased in peroxidative injury, which resulted from the reduction of antioxidative capacities that may be due to the declined glutathione content. Therefore, no significant effects were observed for applied agents in recovery of drained corn plant.
In summary, waterlogging stress causes an accumulation of active oxygen species and lead to an increased lipid peroxidation in the corn plant of Tainan 19. Waterlogging stress also resulted in the reduced activities of enzymatic antioxidants-SOD, AP and GR and altered contents of nonenzymatic antioxidants-ascorbate and glutathione, that lead to reduce capacities of the antioxidative systems and accelerate the peroxidative injury of corn plant.
Many methods were used to overcome or alleviate the waterlogged damage in this thesis. Among them, treatment of direct drainage was found the most economical and effective way. Exogenous treatment with BA, AsA and GSH before waterlogging stress were also effective in alleviating waterlogged damage of corn plant in some extents. And this effect was related to antioxidative systems, especially for glutathione content alteration in the ascorbate-glutathione cycle, which may play an important role in defense and detoxicity. However, the alleviative effects of damage by application of plant growth regulators or active oxygen species scavengers with waterlogging treatment simultaneously was lower than that of pretreatment in Tainan 19 corn seedling. No additional effects were observed in chemical agents application on corn plant with simutaneous draining treatment.
URI: http://hdl.handle.net/11455/36748
Appears in Collections:農藝學系

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