Horticulture Department, Recinto Universitario De Mayaguez, POB 5000, 00709-5000, Mayaguez, Puerto Rico.
Photosynth Res. 1992 Apr;32(1):1-10. doi: 10.1007/BF00028793.
This study was conducted to more clearly define the physiological effects of PS II herbicides on chloroplast thylakoid membrane activity and composition. Barley (Hordeum vulgare L. cv Boone) was grown in hydroponic culture at 20°C in a growth chamber with a light intensity of 500 μmole photons m(-2) s(-1). Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), a Photosystem II herbicide, was supplied continuously via the roots to 7-day-old plants. Atrazine concentrations greater than 0.07 ppm (0.32 μM) were associated with decreased leaf chlorophyll (chl), lowered chl a/b ratio, inhibition of chloroplast electron transport, and plant death within 1 to 2 weeks. Atrazine at 0.07 ppm was defined as sublethal because no toxic effects were observed. Sublethal atrazine induced a decrease in chl a/b ratio with no effect on leaf chl content. Photosynthetic electron transport was either unaffected in fully expanded leaves or slightly stimulated in expanding leaves by treatment of intact plants with 0.07 ppm atrazine. The major effect of sublethal atrazine was on the chl-protein complex composition. Sublethal atrazine increased the level of the Photosystem II light-harvesting complex (LHC-II) and lowered the level of the CP1a Photosystem I complex relative to controls. The numbers of Photosystem II and Photosystem I reaction centers and cytochrome b 6/f complexes per unit chl were not affected by sublethal atrazine. The overall result was an atrazine-induced redistribution of light-harvesting chl from Photosystem I to Photosystem II with no effect on the number of thylakoid membrane-protein complexes associated with electron transport.
本研究旨在更清楚地定义 PS II 除草剂对叶绿体类囊体膜活性和组成的生理影响。大麦（Hordeum vulgare L. cv Boone）在 20°C 的生长室中用强度为 500 μmole photons m(-2) s(-1) 的光在水培中生长。莠去津（2-氯-4-乙氨基-6-异丙氨基-s-三嗪），一种 PS II 除草剂，通过根部连续供应给 7 天大的植物。浓度大于 0.07 ppm（0.32 μM）的莠去津与叶片叶绿素（chl）减少、chl a/b 比值降低、叶绿体电子传递抑制和植物在 1 至 2 周内死亡有关。0.07 ppm 的莠去津被定义为亚致死剂量，因为没有观察到毒性作用。亚致死剂量的莠去津诱导 chl a/b 比值降低，而对叶片chl 含量没有影响。完整植物用 0.07 ppm 莠去津处理，对完全展开的叶片中的光合电子传递没有影响，或对扩展叶片中的电子传递略有刺激。亚致死剂量莠去津的主要影响是在 chl-蛋白复合物组成上。亚致死剂量的莠去津增加了光收集复合物（LHC-II）的水平，并降低了 CP1a 光系统 I 复合物相对于对照的水平。单位chl 的 PS II 和 PS I 反应中心和细胞色素 b 6/f 复合物的数量不受亚致死剂量莠去津的影响。总的结果是莠去津诱导的光收集 chl 从 PS I 向 PS II 的重新分布，而对与电子传递相关的类囊体膜蛋白复合物的数量没有影响。
