本試驗利用14C_嘉磷塞施用於水耕液中，探討水稻(0ηza sativa L. )及 青江菜(Brassica chinensis L.)幼苗根部對嘉磷塞之吸收特性、在植物體內 之累積及分佈情形。結果發現水稻幼苗對嘉磷塞之吸收在初期頗為快速，其 後則較為緩慢，但仍持續增加;青江菜幼苗則隨著處理時間增加，吸收量呈 線性增加。水稻幼苗對嘉磷塞之哎收隨著處理濃度增加亦呈線性增加，並無 達飽和之現象。提高溫度可促進幼苗對嘉磷塞之吸收，經48 (水稻)及50 小時(青江菜)後， QlO值分別為1 .42 及1. 35 。缺氧、DNP 、缺奸、缺磷、 及10 倍磷處理皆會抑制幼苗對嘉磷塞之吸收，但比現象可能部分與蒸散作用 同時受到抑制有關。不論是水稻或青江菜，幼苗吸收嘉磷塞後皆易滲漏出來。 由上述之試驗結果顯示，植物根部對嘉磷塞之吸收為一種被動的生物物理擴 散作用。另外，隨著吸收時間的增加，嘉磷塞在幼苗體內的累積亦明顯提高， 在28 0C 下經48 小時，水稻幼苗體內累積之嘉磷塞濃度比外界溶液濃度高6.3 倍，青江菜經50 小時後比外界濃度高達17.9 倍。由放射顯影圖顯示，嘉磷 塞經根部吸收後，可以很快輸導至全株，並在生長旺盛之部位如生長點、幼 葉累積o

Root uptake of 14C-glyphosate from culture solution by intact rice (0ηJza sativa L.) and ching chiang pakchoí (Brassica chinensis L.) seedlings was investigated to determine the abs。中tion pattem, accumulation and distribution of the herbicide in the plants. Glyphosate uptake by rice roots was rapid and lasted for 12 hours, then followed by a lower but steady rate for the rest of 12-48 hours. Uptake by ching chiang pakchoi roots was also rapid and maintained at a steady rate during the 50 hours absorption period. Higher temperature promoted the absorption. QlO values were 1.42 for rice and 1.35 for ching chiang pakchoi at 48 and 50 hours, respectively. Glyphosate uptake was inhibited by anoxia, DNP (2,4-dínitrophenol), phosphate or potassium defíciency, and lO-fold phosphate treatments. But ít may be partíally correlated with the depression of transpiration. The efflux experiment showed that the absorbed glyphosate was released rapidly to nutrient solution. These results indicated that glyphosate uptake by roots of intact rice and ching chiang pakchoí seedlings was passive, a process of biophysical diffusíon. In addítion, ít was found that glyphosate was readily accumulated ín the plant. At 28 0C for a 48 hours absorption period, the concentration of glyphosate in rice seedlings accumulated to the extent of 6.3 folds higher than that of the treated solution. At the same temperature for 50 hours, ching chiang pakchoi seedlings accumulated 17.9 folds higher than the treated solution. The mechanism of accumulation is still unknown. It is suggested that adsorption or sequestration of the herbicide in plant cells might be involved. Autoradiograms showed that glyphosate was readily transported from roots to whole plant part especially the growing points and young leaves.