Regulation of the growth and photosynthesis of cherry tomato seedlings by different light irradiations of light emitting diodes (LED)

Abstract

The growth and photosynthetic characteristics of cherry tomato seedlings were investigated under seven light irradiations such as dysprosium lamps (white light; control, C), red light emitting diodes (LEDs) (R), blue LEDs (B), orange LEDs (O), green LEDs (G), red and blue LEDs (RB) and red, blue and green LEDs (RBG) with the same photosynthetic photon flux density (about 320 μmol m-2 s-1) for 30 days. Morphological appearances of seedlings were significantly different between light treatments, that is, the plants under RB and RBG were shorter and stronger than those under C, while those under O, G and R were higher and weaker. The higher carbohydrate contents were in plants containing blue treatment, B, RB and RBG. Photosynthetic pigments were shown to have significant difference under respective light irradiations of LEDs. The higher photosynthetic pigments were in leaves of seedlings containing blue light treatment, RBG, RB, B, C and G treatments, the lower the pigments were in those with R and O treatments. Net photosynthesis (Pn) was the highest in leaves of seedlings with RB and RBG and the lowest in those with G. Compared with C treatment, light compensation point and light saturation point of seedlings with R, RB and RBG increased, but those with O and G decreased. Electron transport rate (ETR), quantum efficiency of photosystem II photochemistry (ΦPSII), photochemical quenching (qP) and efficiency of excitation energy capture by open PSII reaction centres (Fv′/Fm′) in seedlings with B, RB and RBG treatments were significantly greater than those of the other treatments. Taken together, RB and RBG of LEDs were shown to be beneficial factors for the growth and photosynthesis in cherry tomato seedlings. Key words : Light-emitting diode (LED), light quality, cherry tomato, growth, photosynthetic characteristics.