Zhang Zi-Shan, Li Yu-Ting, Gao Hui-Yuan, Yang Cheng, Meng Qing-Wei
State Key Lab of Crop Biology, Tai'an, Shandong Province, China.
College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong Province, China.
Sci Rep. 2016 Jul 5;6:26963. doi: 10.1038/srep26963.
Previous investigations on photosynthesis have been performed on leaves irradiated from the adaxial surface. However, leaves usually sway because of wind. This action results in the alternating exposure of both the adaxial and abaxial surfaces to bright sunlight. To simulate adaxial and abaxial surfaces alternant irradiation (ad-ab-alt irradiation), the adaxial or abaxial surface of leaves were exposed to light regimes that fluctuated between 100 and 1,000 μmol m(-2) s(-1). Compared with constant adaxial irradiation, simulated ad-ab-alt irradiation suppressed net photosynthetic rate (Pn) and transpiration (E) but not water use efficiency. These suppressions were aggravated by an increase in alternant frequency of the light intensity. When leaves were transferred from constant light to simulated ad-ab-alt irradiation, the maximum Pn and E during the high light period decreased, but the rate of photosynthetic induction during this period remained constant. The sensitivity of photosynthetic gas exchange to simulated ad-ab-alt irradiation was lower on abaxial surface than adaxial surface. Under simulated ad-ab-alt irradiation, higher Pn and E were measured on abaxial surface compared with adaxial surface. Therefore, bifacial leaves can fix more carbon than leaves with two "sun-leaf-like" surfaces under ad-ab-alt irradiation. Photosynthetic research should be conducted under dynamic conditions that better mimic nature.
先前关于光合作用的研究是在叶片近轴面受光照射的情况下进行的。然而，叶片通常会因风而摆动。这种行为导致近轴面和远轴面交替暴露在明亮的阳光下。为了模拟近轴面和远轴面交替照射（近-远-交替照射），将叶片的近轴面或远轴面暴露于在100至1000 μmol m(-2) s(-1)之间波动的光照条件下。与持续的近轴面照射相比，模拟的近-远-交替照射抑制了净光合速率（Pn）和蒸腾作用（E），但没有抑制水分利用效率。这些抑制作用随着光强交替频率的增加而加剧。当叶片从持续光照转移到模拟的近-远-交替照射时，高光期的最大Pn和E降低，但该时期的光合诱导速率保持不变。光合气体交换对模拟近-远-交替照射的敏感性在远轴面低于近轴面。在模拟近-远-交替照射下，远轴面测得的Pn和E高于近轴面。因此，在近-远-交替照射下，双面叶比具有两个“类阳叶”表面的叶片能固定更多的碳。光合作用研究应在更接近自然的动态条件下进行。
