Agricultural Research Service, United States Department of Agriculture, 27695-7631, Raleigh, North Carolina, USA.
Photosynth Res. 1990 May;24(2):127-36. doi: 10.1007/BF00032593.
Barley seedlings (Hordeum vulgare L. Boone) were grown at 20°C with 16 h/8 h light/dark cycle of either high (H) intensity (500 μmole m(-2) s(-1)) or low (L) intensity (55 μmole m(-2) s(-1)) white light. Plants were transferred from high to low (H → L) and low to high (L → H) light intensity at various times from 4 to 8 d after leaf emergence from the soil. Primary leaves were harvested at the beginning of the photoperiod. Thylakoid membranes were isolated from 3 cm apical segments and assayed for photosynthetic electron transport, Photosystem II (PS II) atrazine-binding sites (QB), cytochrome f(Cytf) and the P-700 reaction center of Photosystem I (PS I). Whole chain, PS I and PS II electron transport activities were higher in H than in L controls. QB and Cytf were elevated in H plants compared with L plants. The acclimation of H → L plants to low light occurred slowly over a period of 7 days and resulted in decreased whole chain and PS II electron transport with variable effects on PS I activity. The decrease in electron transport of H → L plants was associated with a decrease in both QB and Cytf. In L → H plants, acclimation to high light occurred slowly over a period of 7 days with increased whole chain, PS I and PS II activities. The increase in L → H electron transport was associated with increased levels of QB and Cytf. In contrast to the light intensity effects on QB levels, the P-700 content was similar in both control and transferred plants. Therefore, PS II/PS I ratios were dependent on light environment.
大麦幼苗（Hordeum vulgare L. Boone）在 20°C 下，16 h/8 h 光照/黑暗周期，光照强度分别为高（H）强度（500 μmole m(-2) s(-1))或低（L）强度（55 μmole m(-2) s(-1))白光。植物在叶片从土壤中长出后 4 至 8 天的不同时间，从高光强（H → L）和低光强（L → H）下转移。在光周期开始时收获初生叶。从 3 cm 顶端段分离类囊体膜，并测定光合作用电子传递、光系统 II（PS II）莠去津结合位点（QB）、细胞色素 f（Cytf）和光系统 I（PS I）的 P-700 反应中心。整体链、PS I 和 PS II 电子传递活性在 H 中高于 L 对照。与 L 相比，H 植株中的 QB 和 Cytf 升高。H → L 植物对低光的适应在 7 天内缓慢发生，导致整体链和 PS II 电子传递减少，而 PS I 活性则有所变化。H → L 植物的电子传递减少与 QB 和 Cytf 的减少有关。在 L → H 植物中，对高光的适应在 7 天内缓慢发生，整体链、PS I 和 PS II 活性增加。L → H 电子传递的增加与 QB 和 Cytf 水平的增加有关。与 QB 水平对光强的影响相反，两种对照和转移植物的 P-700 含量相似。因此，PS II/PS I 比值取决于光环境。
