Effects of different intensities of far-red and green light on the growth and photosynthetic characteristics of melon seedlings
Shiwen Zhao, Xue Li, Xue Zheng, Ruixian Yu, Yongjun Wu, Zhenchao Yang
Abstract
In order to investigate the effects of different far-red and green light intensities on the growth and photosynthetic characteristics of melon seedlings, 'Emerald ' was used as the test material. Three different intensities of far-red and green light were added basis on a fixed ratio of red to blue light (R:B=4:1) and photosynthetically active radiation (200 μmol/ (m 2 ·s)). The red to far-red light ratios of each treatment were 10 (L-FR), 1.2 (M-FR) and 0.8 (H-FR), respectively. The ratio of green light was set at 10% (L-G), 20% (M-G) and 30% (H-G), corresponding to intensities of 20, 40 and 60 μmol/ (m 2 ·s), respectively. The results showed that: the height of melon seedlings increased significantly with the increase of far-red light intensity, and increasing the proportion of green light in the light quality within the appropriate range could increase both fresh weight and dry weight of seedlings; the palisade tissue, spongy tissue and leaf thickness of melon seedlings showed a decreasing tendency with the increase of far-red light intensity; while increasing the proportion of green light primarily affected the spongy tissue of melon leaves; the stomatal density of melon plants significantly increased with the increase of far-red light intensity in the three treatment groups; Stomatal density significantly increased with higher far-red light intensity in the three treatment groups. Furthermore, the transpiration rate (E), intercellular CO 2 content (Ci), and stomatal conductance (G sw ) all increased with the rising far-red light intensity. While increasing the green light ratio decreased the stomatal pore area, but increased the leaf stomatal density. The net photosynthetic rate of melon seedlings in the M-G treatment was significantly higher than that in the other treatments. In conclusion, appropriately adding far-red and green light during plant growth can enhance seedling growth rate, increasing stomatal density, and improve the photosynthetic capacity of plants.