臭氧對水稻抗氧化酵素影響的研究

Abstract

臭氧對植物的為害除了可從葉部病徵探討外，亦可就植物內部生理、生化反應進行評估。本論文選取?稻台農67號（TNG. 67）及秈稻台中在來1號（TCN. 1）兩種水稻品種，利用連續攪拌熏氣箱系統，以臭氧熏氣處理；觀察外表傷害程度、電解質滲漏率、失水度及測定葉部抗氧化酵素活性的增加量等，以此比較品種間感受度之差異。 以臭氧處理後的水稻，葉子外表最先會有白色細點斑的急性病徵，進而褐斑、黃化、枯萎等現象且葉子會有失水、電解質滲漏發生，為瞭解組織內酵素活性改變情況，分別以臭氧濃度之變化、熏氣時間的長短、及不同株齡、葉齡、品種間差異性之比較。數據顯示臭氧處理過的水稻，葉子的superoxide dismutase及peroxidase活性皆明顯增加，所增加的SOD活性，以Mn-SOD最明顯，而所增加的peroxidase活性，ascorbate peroxidase只是其中的部分；而臭氧濃度較高、熏氣時間較長者SOD、peroxidase活性之增加量較高，株齡較低者有較敏感的反應，而同一植株上的成熟葉亦較頂端的年輕葉敏感，外表型的傷害和酵素活性之提升，均以成熟葉較明顯；然根部卻無似葉子般的酵素活性改變情形。在蛋白質的變化上，經臭氧處理後之樣品，顯示在大約28 KD處，其量有增加的趨勢，TCN. 1尤其明顯。以tissue printing assay之方法，測定葉部H2O2之量，結果實驗組與對照組皆不呈現顏色之差異。 本研究的試驗條件下，TNG. 67與TCN. 1兩者對臭氧之敏感度差異並不明確，TNG. 67外部形態有較嚴重的受傷程度，電解質與含水量也有較大的漏失程度；然而TCN. 1卻有較快的病徵出現，以及額外的catalase活性、及蛋白質含量之提升。而兩者的抗氧化酵素SOD、peroxidase活性的變化情形也相似，所以在本文中所使用的處理條件、比較項目下，似乎難以界定TNG. 67與TCN. 1何者對臭氧是較具感受性的。

Some antioxidant enzymes attributed by plants, such as superoxide dismutase (SOD), peroxidase and catalase, metaboblize superoxide and hydrogen peroxide individually. These enzymes may offer plants resistance to the enviromental stress. In this study, two strains of rice (Oryza sativa L.), Tainung 67 (TNG. 67) and Taichung Native 1 (TCN. 1) are fumigated with ozone under continuous stirred tank reactors system. Sensitivity differences between these two strains were compared according to the increase in antioxidant enzyme activity, the level of dehydration, electrolyte leakage rate and injury symptom in their morphology of treated leaves. After ozone fumigation, the appearance of rice leaves first showed tiny white stipples as an acute injury symptom, and subsequently showed red-purple stipples, chlorosis and wilting. In the meantime, there were loss of water and leakage of electrolytes. In the leaves of fumigated rice, there were increases of SOD and peroxidase activity. Among these increases of SOD enzyme activities, Mn-SOD activity appeared to be the most pronounced and ascorbate peroxidase was just a minor part of the increase peroxidase activity. A higher ozone concentration or a longer fumigation duration brought SOD and peroxidase activities much greater. Young plants were more sensitive than old ones. Within the same plant, mature leaves were more sensitive than young leaves on the apex. The external injury and the increases of enzyme activity were more obvious with the mature leaves, too. However, there were no changes of these enzyme activities in the roots. In the aspects of protein, samples taken after ozone fumigation showed an increase in the polypeptide having MW. about 28 KDa, and the increase in TCN. 1 was much pronouced Tissue printing assay was used to measure endogenous H2O2 amount in leaves, and which showed no difference between the experiments and the control. Under conditions designed in this study, TNG. 67 was much seriousely damaged on morphology, and the leakage of both eletrolytes and water content were higher in TNG. 67 than in TCN. 1. While the injury symptoms appeared earlier in TCN. 1, the elevated catalase activity and enhanced amount of 28 KDa polypeptide were also higher in TCN 1. The enhanced enzyme activity of SOD and peroxidase showed similarity in both strains. Consequently, it seems difficult to conclude which one of TNG. 67 and TCN. 1 is more sensitive to ozone treatments.