- 學位論文
重金屬處理對四種植物抗氧化防禦系統的影響
The Influence of Heavy Metal Treatment on the Antioxidant Defense System of Four Plants
摘要
工業非法排放未經處理的廢水或事業廢棄物，導致附近農地在引水灌溉時遭受重金屬汙染。在臺灣，農地汙染場址以重金屬鎘 (Cd) 、銅 (Cu) 、鉻 (Cr) 、鎳 (Ni) 、鋅 (Zn) 、鉛 (Pb) 之汙染為最。大部分的植物暴露於重金屬汙染會產生含氧的自由基，造成氧化壓力 (oxidative stress)。然而植物發展出一套抗氧化防禦系統來抵抗重金屬逆境，其中包含許多抗氧化酵素如超氧化物歧化酶 (superoxide dismutases, SOD) 、過氧化氫酶 (catalase, CAT) 、抗壞血酸過氧化酶 (ascorbate peroxidases, APX) 以及穀胱甘肽還原酶 (glutathione reductase,GR) 等，協助清除植物體內過多的活性氧 (Reactive oxygen species)。 本研究選擇相思樹 (Acacia confusa) 、水黃皮 (Pongamia pinnata) 、三年桐 (Aleurites fordii) 、狼尾草 (Pennisetum purpureum) 四種能源植物，探討抗氧化酵素協助植物抵抗氧化逆境時的活性變化，以及植物吸收並累積重金屬於葉部的含量，對四種植物進行比較。結果顯示四種植物的SOD活性在不同濃度處理下沒有顯著差異，表示各樹種在重金屬逆境下細胞中的活性氧分子皆升高，SOD活性的表現也隨之增加。整體而言CAT活性在樹種間有差異，不同濃度間也有差異，每個樹種展現不同的反應能力與 SOD 協力清除植體內有害的O2-和 H2O2 。GR在對照組與其他濃度處理皆有差異，GR活性的提高幫助完成ascorbate–glutathione cycle的最後去毒階段。 酵素SOD、CAT、APX以及GR的協同作用，大多可幫助植物清除體內過多的活性氧，抵抗氧化逆境，避免細胞損傷。然而，因不同植物的特性，因此一植物只對一、兩種重金屬有較好的吸收能力。總括來看，僅水黃皮能夠對Cu有吸收效果；Cr的部分只有相思樹能夠吸收；Ni可由三年桐和狼尾草吸收，以三年桐的吸收量較高；而雖然四種植物都有發現Pb含量，但狼尾草吸收鉛的平均值高於其他樹種，而水黃皮和三年桐無顯著差異，重金屬Pb屬狼尾草有較佳的吸收能力。
並列摘要
Illegal discharge of untreated industrial waste water or industrial waste, leads to farmland nearby suffered heavy metal contamination during irrigation. In Taiwan, agricultural land sites contaminated with the pollution of cadmium (Cd) , copper (Cu) , chromium (Cr) , nickel (Ni) , zinc (Zn) , lead (Pb) the most. Most of the plants expose to heavy metal pollution will produce oxygen free radicals, resulting in oxidative stress . However, plants develop a series of antioxidant defense system to resist the heavy metal stress, which contains many antioxidant enzymes such as superoxide dismutase (SOD) , catalase (CAT) , ascorbate peroxidase (APX) and glutathione reductase (GR) , to assist plants removing excessive reactive oxygen species . In this study, four energy plants including Taiwan Acacia (Acacia confusa) , Poonga Oil Tree (Pongamia pinnata) , Tung Oil Tree (Aleurites fordii) , and Napier Grass (Pennisetum purpureum) were treated with heavy metals, discuss the reaction of antioxidant defense system, as well as the antioxidant enzyme activity of plants against oxidative stress. Heavy metal accumulation of four plants were investigated and compared. The results indicate that SOD activity has no significant difference in four plants under different concentrations, which represent the rise of reactive oxygen species, and increase the performance of the SOD activity . The CAT activity has significant difference between four plants, as well as different concentrations, which indicate each species show a different ability to cope with SOD to clear potential harmful O2- and H2O2. GR has significant difference between the control and other concentration, high GR activity maintain the depletion stage of glutathione, completing the final stage of ascorbate-glutathione cycle. With the cooperation of SOD, CAT, APX and GR in plant, most plants can help get rid of the excess reactive oxygen species against oxidative stress, preventing plant cell from damage. However, due to the characteristics of different plants, a plant only has a better ability to absorb and accumulate one or two heavy metals. In conclusion, only Pongamia pinnata has the better absorption effect of Cu. Cr can be absorbed only by Acacia confusa. Ni can be accumulated by Aleurtes fordii and Pennisetum alopecuroides, but the average value is higher in Aleurites fordii. Although Pb can be found in four plants, the average value of Pennisetum alopecuroides is higher than the other plants. There is no significant differences between Pongamia pinnata and Aleurites fordii, and Pennisetum alopecuroides have a better Pb absorption capacity.