Song Yu, Jiang Chengyao, Gao Lihong
College of Horticulture, China Agricultural UniversityBeijing, China; Institute of Germplasm Resources, Xinjiang Academy of Agricultural ScienceUrumqi, China.
Graduate School of Horticulture, Chiba University Matsudo, Japan.
Front Plant Sci. 2016 Dec 9;7:1832. doi: 10.3389/fpls.2016.01832. eCollection 2016.
Light insufficient stress caused by canopy interception and mutual shading is a major factor limiting plant growth and development in intensive crop cultivation. Supplemental lighting can be used to give light to the lower canopy leaves and is considered to be an effective method to cope with low irradiation stress. Leaf photosynthesis, stomatal regulation, and plant growth and development of young tomato plants were examined to estimate the effects of supplemental lighting with various composite spectra and different light orientations. Light-emitting diodes (LEDs) of polychromatic light quality, red + blue (R/B), white + red + blue (W/R/B), white + red + far-red (W/R/FR), and white + blue (W/B) were assembled from the underneath canopy or from the inner canopy as supplemental lighting resources. The results showed that the use of supplemental lighting significantly increased the photosynthetic efficiency, and reduced stomatal closure while promoting plant growth. Among all supplemental lighting treatments, the W/R/B and W/B from the underneath canopy had best performance. The different photosynthetic performances among the supplemental lighting treatments are resulted from variations in CO utilization. The enhanced blue light fraction in the W/R/B and W/B could better stimulate stomatal opening and promote photosynthetic electron transport activity, thus better improving photosynthetic rate. Compared with the inner canopy treatment, the supplemental lighting from the underneath canopy could better enhance the carbon dioxide assimilation efficiency and excessive energy dissipation, leading to an improved photosynthetic performance. Stomatal morphology was highly correlated to leaf photosynthesis and plant development, and should thus be an important determinant for the photosynthesis and the growth of greenhouse tomatoes.
冠层截留和相互遮荫导致的光照不足胁迫是集约作物栽培中限制植物生长发育的主要因素。补光可用于照亮冠层下部叶片，被认为是应对低光照胁迫的有效方法。研究了幼龄番茄植株的叶片光合作用、气孔调节以及植株生长发育情况，以评估不同复合光谱和不同光照方向的补光效果。将多色光质的发光二极管（LED），即红+蓝（R/B）、白+红+蓝（W/R/B）、白+红+远红（W/R/FR）和白+蓝（W/B），从冠层下方或冠层内部组装作为补光光源。结果表明，使用补光显著提高了光合效率，减少了气孔关闭，同时促进了植株生长。在所有补光处理中，来自冠层下方的W/R/B和W/B表现最佳。补光处理间不同的光合性能是由CO利用的差异导致的。W/R/B和W/B中增强的蓝光比例能更好地刺激气孔开放，促进光合电子传递活性，从而更好地提高光合速率。与冠层内部处理相比，来自冠层下方的补光能更好地提高二氧化碳同化效率和过剩能量耗散，从而改善光合性能。气孔形态与叶片光合作用和植株发育高度相关，因此应是温室番茄光合作用和生长的重要决定因素。
