(4) Polycyclic disease

7. 下面兩段文章摘選自 Pacific Northwest Plant Disease Management Handbook，請將其翻譯成中文(專有名詞盡量使用中文名，沒有中文者可直接寫英文名稱)(8分)？Phosphorus (abbreviated P) is one of the essential elements for normal growth and development of plants and normally found in the form of phosphoric acid (H₃PO₄). The amount of phosphorus a fertilizer contains is represented as the middle number on the bag expressed as P₂O₅ (such as 5-10-15 where the first number represents the nitrogen percentage and the third number potassium percentage as K₂O. The P₂O₅ unit used to represent P content in fertilizer is a conventional unit (in reality, there is little or no P in the form of P₂O₅ in fertilizer).Phosphoric acid should not be confused with phosphorous acid (H₃PO₃). A single letter difference in the name of a chemical compound can make a big difference in its properties. It is well documented that phosphorous acid is able to control diseases caused by organisms that belong to the Oomycetes that are on agronomical crops. For example, phosphorous acid was shown to be effective when applied as a root drench against Phytophthora cinnamomi, P. nicotianae, and P. palmivora in lupin (羽扇豆), tobacco, and papaya, respectively. Phosphorous acid has both a direct and an indirect effect on oomycetes. Phosphorous acid releases the phosphonate ion (HPO₃⁻-2), also called phosphite, upon disassociation. Like phosphate, phosphonate is easily taken up and translocated inside the plant. Because phosphonate is systemic and stable in plant, it should be applied infrequently. A clear distinction exists between phosphoric acid and phosphorous acid. Claims suggesting that either compound may fulfill the functions of the other are not supported by current literature and are therefore misleading.

(4) Polycyclic disease

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