Liu Zhiqian, Gaskin Robyn E
New Zealand Forest Research Institute, Private Bag 3020, Rotorua, New Zealand.
Pest Manag Sci. 2004 May;60(5):434-9. doi: 10.1002/ps.816.
The diffusion of two fluorescent dyes, Oregon Green 488 (Oregon Green) and Rhodamine B into the leaves of broad bean (Vicia faba L) plants was studied to simulate the foliar uptake process of pesticides. The uptake rate of these model xenobiotics into bean foliage was measured using a standard leaf surface wash-off method. Diffusion into leaf tissues was visualised in vivo by confocal laser scanning microscopy (CLSM). The moderately lipophilic dye (Rhodamine B) showed faster uptake than the hydrophilic one (Oregon Green), despite the former being a larger molecule. While no distinct channels or domains for preferential entry of any of the dyes could be detected in the cuticle layer by CLSM, two different diffusion patterns were identified for the movement of these two dyes after traversing the cuticle. Upon desorption from the cuticle, Rhodamine B diffused extensively into the vacuole of the epidermal cells. Further transport of this dye from the epidermal cells to the mesophyll cells was not observed. In contrast, Oregon Green was found in the epidermal cell walls and cytoplasm, and was also present in the mesophyll cells. Examination of the petioles of the treated leaves revealed that, once absorbed, Oregon Green moved readily out of the treated leaf, whereas Rhodamine B did not show any phloem translocation. It is proposed that these two different diffusion characters may be responsible for the contrasting phloem mobility of the two xenobiotics. The results are discussed in relation to the current knowledge on the uptake, translocation and efficacy of pesticides as influenced by their properties.
研究了两种荧光染料,即俄勒冈绿488(Oregon Green)和罗丹明B向蚕豆(Vicia faba L)叶片中的扩散情况,以模拟农药的叶面吸收过程。使用标准的叶片表面冲洗方法测量了这些模型异生物质进入豆叶的吸收率。通过共聚焦激光扫描显微镜(CLSM)在体内观察了染料向叶组织中的扩散情况。尽管罗丹明B是较大的分子,但这种中等亲脂性染料的吸收速度比亲水性染料(俄勒冈绿)更快。虽然通过CLSM在角质层中未检测到任何一种染料优先进入的明显通道或区域,但在这两种染料穿过角质层后的移动过程中,确定了两种不同的扩散模式。从角质层解吸后,罗丹明B广泛扩散到表皮细胞的液泡中。未观察到这种染料从表皮细胞进一步转运到叶肉细胞。相比之下,俄勒冈绿存在于表皮细胞壁和细胞质中,也存在于叶肉细胞中。对处理过的叶片叶柄的检查表明,一旦被吸收,俄勒冈绿很容易从处理过的叶片中移出,而罗丹明B没有显示出任何韧皮部转运。有人提出,这两种不同的扩散特性可能是这两种异生物质在韧皮部中移动性不同的原因。结合目前关于农药的吸收、转运及其性质对药效影响的知识,对结果进行了讨论。