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Effects of different Nitrogen Source on Enzyme Activities in Nitrogen Metabolism of Drosera spathulata Lab. and Drosera burmanni Vahl
|摘要:||以台灣原生小葉毛氈苔（Drosera spathulata Lab.）及寬葉毛氈苔（Drosera burmanni Vahl）為材料，利用組織培養方式以MS培養基做為對照及增殖，另外以缺氮、氨態氮、硝態氮及有機peptone等不同氮源處理，連續處理六週後再移回MS培養基培養四週，每週採樣，以比較處理期和恢復期氮代謝酵素：NR、NiR、GS、NADH-GOGAT及NADH-GDH活性變化，並在恢復期比較幼葉及成熟葉的酵素活性恢復情形。
Drosera spathulata Lab. and Drosera burmanni Vahl were used and allowed to grow in MS mediums as control groups. Four other nitrogen conditions-- nitrogen deficiency, ammonium, nitrate, and organic peptone--were set so that a series of comparisons of nitrogen metabolic enzyme activities, such as nitrate reductase (NR), nitrite reductase(NiR), glutamine synthase(GS), NADH-glutamate synthase (NADH-GOGAT), and NADH-glutamate dehydrogenase (NADH-GDH), between young leaves and mature ones could be made after six successive weeks of experiment and another four weeks' growth back in MS mediums. The conditions young leaves and mature ones recover during their convalescence were also compared. In ammonium environment, a few sundews turned brown and died while others grew slowly and had fragile stems; in nitrate environments, some sundews died while others grew hard and brittled with a tendency of early blossom. In organic peptone environment, plants grew slightly better; in nitrogen deficient environment, sticky gland on the surface of leaves became red, plants ceased growing and no new leaf grew. NR and NiR enzyme activities were induced by NO3-, as a result, leaves showed higher enzyme activities in nitrate environment. The highest enzyme activity of NR was 77% that of MS grown in the same period. The highest enzyme activity of NiR was 139% that of MS. In nitrogen deficient and organic peptone environments however, enzyme activities decreased. The highest NR enzyme activities was 61% while enzyme activities of NiR enzyme activity was 76% compared to MS's enzyme activity. The performances of GS enzyme activities of two different sundews were similar. The GS enzyme activity of Drosera spathulata Lab. ranges from 14 to 17(μmole/hr.g) ,and the GS enzyme activity of Drosera burmanni Vahl fell from 15 to 16(μmole/hr.g). The NADH-GDH enzyme activity of Drosera spathulata Lab. was between 0.7 and 1.5(μmole/hr.g) while that of Drosera burmanni Vahl ranges from 1.0 to 1.4(μmole/hr.g),indicating that NH4+ of these two kinds of sundews were stabilized by the GS. The enzyme activity performances of NADH-GOGAT weren't distinct for Drosera burmanni Vahl in different growing environments. Yet, Drosera spathulata Lab. only showed higher enzyme activities in nitrate and ammonium environments. In nitrogen deficient and organic peptone environments, enzyme activities of Drosera spathulata Lab. tends to be lower. These show that NADH-GOGAT enzyme activity of Drosera spathulata Lab. decreases when nitrogen supply is insufficient and when there is enough organic peptone. On the other hand, Drosera burmanni Vahl could still obtain its normal enzyme activity level. During the convalescence, levels of enzyme activities of both kinds of sundews recovered quickly in four weeks. The growth and enzyme recovering speed of young leaves were far beyond those of mature leaves, indicating that proteins are formed abundantly when young leaves growing.
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