水耕栽培中銨態氮（NH4+-N）對溫室洋香瓜根代謝反應之影響

Influences of Amonium Nitrogen Strength on the Muskmelon Root Metabolism with Hydroponics

溫室洋香瓜（Cucumis melo L. cv. Asuka）以不同濃度的銨態氮作為營養液處理，探討氨態氮對溫室洋香瓜根代謝反應之影響，由結果顯示，水耕栽培養液中銨態氮高於32mM時，導致根之呼吸率降低、根生長受到抑制、蘋果酸含量減少；根組織中NADP-ME活性、酒精去氫酶活性、乙醛、酒精含量增加：丙酮酸、乳酸含量則無顯著變化。顯示，對溫室洋香瓜（Asuka）而言，銨態氮濃度超過32mM，易導致根細胞碳水化合物代謝作用改變，進行無氧呼吸產生乙醛及乙醇，致使根生長受抑制。由本研究獲知，Asuka溫室洋香瓜，其水耕栽培養液中建議銨態氮濃度以16mM為宜。

The muskmelon (Cucumis melo L. cv. Asuka) was grown hydroponically by varying ammonium nitrogen strength to determine the influences of it on the muskmelon root metabolism. The results of the experiment showed that the strength of ammonium nitrogen over 32 mM of the nutrient solution it resulted in decrease of the respiratory rate and growth, and malate content of root. Oppositely, the activity of NADP-malic enzyme, alcohol dehydrogenase, and the level of acetaldehyde, ethanol were increased, but the levels of both lactate and pyruvate appeared no significant difference from that of check plot. It implied that at a strength of ammonium nitrogen over 32 mM the roots of muskmelon had an anaerobic metabolism that resulted in the increasing of the end products of both acetaldehyde and ethanol, and in inhibiting the root growth of muskmelon which might result from a deterioration of carbohydrate metabolism. Therefore, based on the results it is recommend that the strength of 16 mM ammonium nitrogen nutrient solution will be suitable for the cultivation of muskmelon cv. Asuka hydroponically.