Riederer M, Schönherr J
Ecotoxicol Environ Saf. 1985 Apr;9(2):196-208. doi: 10.1016/0147-6513(85)90022-3.
Diffusion of (2,4-dichlorophenoxy)acetic acid (2,4-D) across plant cuticles from 10 species was investigated at 25 degrees C using enzymatically isolated cuticles. Permeance coefficients (P) and extrapolated holdup times (te) were measured and permeability (P), diffusion (D), and partition coefficients (K) were calculated. Permeance coefficients ranged from 2.72 X 10(-8) (Capsicum fruit) to 1.00 X 10(-10) m/sec (Ficus leaf). Extraction of soluble cuticular lipids from cuticular membranes increased permeances by up to four orders of magnitude. This demonstrates that permeance is determined by the soluble cuticular lipids associated with the cutin, rather than by cutin alone. Mean diffusion coefficients calculated from holdup times were 4.0 X 10(-15) (fruit cuticular membranes) and 1.71 X 10(-16) m2/sec (leaf cuticular membranes), respectively. Since a common diffusion coefficient exists for both leaf and fruit cuticles, differences in permeability coefficients between species can be attributed to differences in the partition coefficients. However, partition coefficients calculated from transmembrane diffusion are lower than those determined directly in a sorption experiment by a factor of from 6 to 200. Thus, the high resistance of plant cuticles to transport of 2,4-D can be attributed to both low diffusion and partition coefficients in the transport-limiting layer made up of cutin and soluble lipids which are densely packed and highly ordered. A linear equation is derived and permits the prediction of permeability coefficients of plant cuticles from partition coefficients determined in a simple sorption experiment.
在25摄氏度下，使用酶法分离的角质层研究了10种植物角质层对（2,4-二氯苯氧基）乙酸（2,4-D）的扩散。测量了渗透系数（P）和外推保留时间（te），并计算了渗透率（P）、扩散系数（D）和分配系数（K）。渗透系数范围从2.72×10⁻⁸（辣椒果实）到1.00×10⁻¹⁰米/秒（榕树叶）。从角质层膜中提取可溶性角质层脂质可使渗透率提高多达四个数量级。这表明渗透率由与角质相关的可溶性角质层脂质决定，而非仅由角质决定。根据保留时间计算的平均扩散系数分别为4.0×10⁻¹⁵（果实角质层膜）和1.71×10⁻¹⁶平方米/秒（叶片角质层膜）。由于叶片和果实角质层存在共同的扩散系数，物种间渗透率系数的差异可归因于分配系数的差异。然而，通过跨膜扩散计算的分配系数比在吸附实验中直接测定的分配系数低6至200倍。因此，植物角质层对2,4-D运输的高抗性可归因于由紧密堆积且高度有序的角质和可溶性脂质组成的运输限制层中低扩散系数和分配系数。推导了一个线性方程，可根据在简单吸附实验中测定的分配系数预测植物角质层的渗透率系数。
