Abstract
Because the leaf arrangement of Phalaenopsis shows a large extent of overlap, a great portion of lower leaves often stay in the shade of upper leaves. This makes the light received by lower leaves is usually very low, thereby greatly limits their photosynthetic productivity. In this research, we used in vivo chlorophyll fluorescence to detect the photosynthesis of Phalaenopsis. We found that lower leaves obviously exhibited lower rate in photosynthesis than upper leaves. However, we also found that Phalaenopsis showed great plasticity in this respect. As long as higher daily light intensity is provided to lower leaves for a certain period, their photosynthesis rate can be significantly improved. Besides, elevating the lower leaves’ daily light intensity can also make them less vulnerable to photoinhibition.In Phalaenopsis, the quality of flowers depends on sufficient storage of carbohydrate in the plant. Especially the lower leaves closest to flower stalks take the greatest responsibility. Therefore, elevating the intensity of light received by lower leaves should help to promote the growth and flowers’ quality of Phalaenopsis. However, Phalaenopsis exhibited photoinhibition under low light intensity. Providing higher light intensity from top may increase the light received by lower leaves, but it may also damage upper leaves at the same time. So it would be better to increase the lateral light around Phalaenopsis singly so that both upper and lower leaves of Phalaenopsis are all illuminated with proper light intensity. In the research, we used mirrors to increase the lateral light, and found that this treatment indeed improved the overall photosynthetic productivity of plant, but without significant improvement on the flowers’ quality. The reason should be studied further.