番茄有效根群分佈之放射追蹤及活株現場測定法

Quantitative Estimation of Functional Root Distribution of Tomato Plants by Radiotracer and In-situ Detection Methods

作物根群分佈密集狀況之調查研究，已成為田間有效施肥之先決步驟，本試驗係以二不同生長階段之Roma番茄為試材，循放射追蹤法，由地上部主經注射某一劑量之放射性核種，再環繞植株鑽取不同距離及深度之土壤樣品，根據一定體積之含根土壤比活性，以推斷作物有效根群分佈密集區域，作為有效施肥之參考，同時並比較洗根及現場活株測定之可行性，以及32P，86Pb二核種之顯跡效應，其結果略為：1.根據圍繞植株四週不同遠近深淺之含根土壤比活性，足以為根群密集情形之推斷，各次試驗結果均顯示株高60~130公分之Roma番茄，其有效根群密集於離主經12.5公分而又散佈於土面下0~10公分一帶。植物根群分佈習性隨品種，生長階段或樹齡，以及土壤特性，自然環境因素等所影響，應無特異現象，故若土壤取樣得宜，當可循含根土壤之放射比活性之強弱，推斷根群密集狀況。2.洗根法繁瑣實時，況因所檢取之根群未必為所屬作物者，且究具否機能仍屬可疑，此點已由放射比活性之測定，而證明其可異性不高。3.本試驗所設計採用之側窗GM管，用作現場活株之直接探測，碓能應驗由灰化土壤比活性測定之結果，如設備改進，不失為簡便之根群分佈放射追蹤測定方法。4.32P或80Rp作為追蹤核種，均具有迅速下達，均勻分佈，便以測定之優良效果，惟86Rb所發射加碼光子之能量甚高，如施用劑量較高時，對工作人員這保鍵，宜有顧忌。供試場地之土層分析結果，亦能驗證各次試驗中放射測定有效根群分佈狀況之結果。

An investigation of the functional root distribution and extent of the crops has been considered as a necessary proceeding before implementing the effective fertilization Roma tomatoes of two growing stages were used as the materials in this study, The experiments were carried out by radiotracer technique. A certain dose of radionuclide was injected into the stem the soil columns of various depths and distances around the stem were then taken after absorption and translocation. Based upon the specific activeity of the ashed soil samples, the area of functional and dense root systems could be judged. The information above may be helpful in bringing on the effective fertilization. On the hand, the reliability of root washing method, the feasibility of the in-situ detection as well as the tracing effect of either phosphorus-32 or rubidium-86 were studied in this research. The results are briefly mentioned below: 2. Root washing is a very tedious and time-consuming work. It is due to the questionable origin and function of the roots which cause this method unreliable. 3. The in-situ detection using a side-window GM tube designed in this experiment can be considered as an effective and easy-operation method since the readings corresponded with the specific activities of the eshed soil sample. But the equipment adopted in this study is still to be improve. 4. Both phosphorus-32 and rubidium-86 characterizing in rapid translocation, even distribution in plant tissue and easy to detect by a GM counter, had been proved as the ideal tracers, But a proper protection for the workers should be taken into consideration when using rubidium-86 as a tracer due to its high energy gamma radiation. The soil profile analysis at the testing site had also confirmed the results obtained in all the experiments.