Department of Plant Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5.
Plant Physiol. 1987 Sep;85(1):82-6. doi: 10.1104/pp.85.1.82.
The herbicides chlorsulfuron and clopyralid were taken up rapidly by excised pea root tissue and accumulated in the tissue to concentrations ten and four times those in the external medium, respectively. Uptake was related linearly to external herbicide concentration over a wide concentration range, implying that transport across the membrane is by nonfacilitated diffusion. Uptake of both compounds was influenced by pH, with greatest uptake at low pH. The pH dependence of uptake suggests that the herbicides (both of which are weak acids) are transported across the plasma membrane in the undissociated form, and accumulate in the cytoplasm by an ion trap mechanism. Most of the absorbed herbicide effluxed from the tissue when it was transferred to herbicide-free buffer, indicating that the accumulation was not due to irreversible binding. Consequently, both herbicides remain available for transfer to the phloem. These results can explain the high reported phloem mobility of clopyralid in intact plants. The low phloem mobility of chlorsulfuron must be accounted for by factors that override its ability to accumulate in the symplast.
除草剂氯磺隆和氯吡啶酸被豌豆离体根组织迅速吸收，并分别积累在组织中的浓度是外部介质中的 10 倍和 4 倍。在较宽的浓度范围内，吸收与外部除草剂浓度呈线性关系，这意味着跨膜运输是通过非促进扩散进行的。两种化合物的吸收均受 pH 值影响，在低 pH 值下吸收最大。吸收的 pH 值依赖性表明，这些除草剂（均为弱酸）以未离解的形式穿过质膜运输，并通过离子阱机制积累在细胞质中。当组织转移到不含除草剂的缓冲液中时，大部分吸收的除草剂从组织中流出，表明积累不是由于不可逆结合。因此，两种除草剂均可用于转移到韧皮部。这些结果可以解释氯吡啶酸在完整植物中报告的高韧皮部移动性。氯磺隆的韧皮部移动性较低，这必须归因于其在质外体中积累的能力被其他因素所超越。
