Abstract
Sunflower seedlings (Helianthus annuus L. cv. Russian Mammoth) were grown under two different lamps of a 4-band fluorescent lamp with a red/far-red photon flux ratio (R/FR) of 1.10 and a 3-band fluorescent lamp with a R/FR of 12.5. Photosynthetic photon flux density (PPFD) was kept at 160μmol m-2 s-1 in both treatments. The stomatal density and stomatal aperture were measured with a microscope after 6 days of treatment. After 7 days of treatment, the stomatal conductance was measured with a porometer. Then the transpiration rate and photosynthetic rate were also measured under a metalhalide lamp, when PPFD was kept at 300 μmol m-2 s-1. Compared with the 3-band fluorescent lamp, the plants grown under the 4-band fluorescent lamp increased in top fresh weight, top dry weight and shoot length for the sunflower. The stomatal density and stomatal aperture increased for plants grown under the 4-band fluorescent lamp. The stomatal conductance, transpiration rate and photosynthetic rate of the plants grown under the 4-band fluorescent lamp were greater than under the 3-band. In this study, we found that FR radiation affected the features of the stomata, and as a result, increased the transpiration rate and photosynthetic rate.
