Effects of different intensities of far-red and green light on the growth and photosynthetic characteristics of melon seedlings

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 mu mol/ (m2 & sdot;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 mu mol/ (m2 & sdot;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 CO2 content (Ci), and stomatal conductance (Gsw) 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.