Dissipation of Glyphosate Injected into the Lead Tree (Leucaena leucocephala) in Different Seasons in Taiwan

台灣不同季節下嘉磷塞注入銀合歡(Leucaena leucocephala)後之消褪變化

陳榮芳(Rong-Fang Chen) ； 王相華(Hsiang-Hua Wang) ； 王慶裕(Ching-Yuh Wang)

《台灣林業科學》 23卷4期 (2008/12) Pp. 287-299

https://doi.org/10.7075/TJFS.200812.0287

摘要

銀合歡(Leucaena leucocephala(Lam.)de. Wit)為長久存在台灣之外來植物，為了決定適當之控制方式本研究分別於春季及夏季採用三種不同濃度之嘉磷塞除草劑，在施用總量相同(18.8mmole)之情況下，比較其控制效果並監測除草劑殘量流向。試驗結果顯示於春季以未稀釋之嘉磷塞除草劑直接注射銀合歡樹幹可以獲得良好控制效果。根據注射後分析植株上部(於上方注射孔上方25cm處)、中部(兩注射孔中間)及下部(於下方注射孔下方25cm處)三處之韌皮部與木質部，以及林區土壤，顯示除草劑於注射後即快速消褪，尤其夏季高溫及因颱風引來之雨量更加速其消褪。春季試驗發現銀合歡植株與土壤中之嘉磷塞在一年內降至ppm濃度，而在夏季試驗更明顯縮短時間；因此可以排除嘉磷塞污染土壤環境之可能性。分析嘉磷塞在植株不同部位之韌皮部與木質部之分布變化，推測嘉磷塞於注射後逐漸向上、下方擴散，以及由木質部往韌皮部側向擴散，於長距離轉運之前似乎嘉磷塞會優先擴散及累積於注射孔附近之韌皮部。

關鍵字

嘉磷塞 ； 注射 ； 韌皮部 ； 木質部 ； 轉運

並列摘要

To determine the appropriate way to control the lead tree (Leucaena leucocephala (Lam) de. Wit), an invasive plant in Taiwan, 3 concentrations with an equal amount of glyphosate (18.8 mmole) were applied in spring and summer, respectively, and glyphosate residues in the plants and soils were monitored. A good control effect was observed with injecting a commercial product of glyphosate without dilution, especially in spring. Measurements of glyphosate residues in the upper (25 cm above the upper injection hole), middle (between the 2 injection holes), and lower (25 cm below the lower injection hole) parts of the lead tree, as well as in forest soils in spring and summer experiments showed that this herbicide began to sharply dissipate after treatment, which was accelerated by high temperatures and heavy rainfall from typhoons. In the spring experiment, it required ca. 1 yr for glyphosate residues in both the lead trees and soils to drop to a few parts per million, while this period was further shortened in the summer experiment. Thus, there is only a small possibility of glyphosate pollution of the soil environment of lead tree forests. Analysis of glyphosate in xylem and phloem from different parts of the plants revealed that after injection, glyphosate gradually diffused acropetally, basipetally, and laterally from the xylem tissue to the surrounding phloem tissue. Glyphosate appeared to preferentially diffuse to and accumulate in phloem near the injection hole for further long-distance translocation in phloem tissue.

並列關鍵字

glyphosate ； injection ； xylem ； phloem ； translocation