Effect Different Spectral LED on Photosynthesis and Distribution of Photosynthate of Cherry Tomato Seedlings

Adopting C-14 isotope tracer and microradioautography technique, photosynthesis, photosynthate distribution pattern of cherry tomato seedlings were investigated under dysprosium lamp (white light control, C) and five LED light treatments designated as red (R), blue (B), orange (Y), green (G), red and blue (RB) with the same photosynthetic photon flux density (PPFD) for 30 days. Compared with C, the Pn and stomata density were increased under RB and B and was stable under R, while those of Y and G were reduced. The changes of Pn and growth in cherry tomato seedlings were related with the photosynthetic pigment content, stomata number, photosynthate distribution and light energy regulation of photo system II. Higher photosynthetic pigment content and more stomata number under light treatments had higher the net photosynthetic rate (Pn). Furthermore, the suitable photosynthate distribution and translocation had feedback impact on the photosynthesis. The ratios of photosynthate distributed in leaves of RB, B and R were significantly higher than those of other treatments. The photosynthate labeled by C-14 transported to the leaves and roots of the RB and B treatments, while Y and G treatments still kept the C-14 in the labeled leaf. The result suggested that growth of cherry tomato seedlings was significantly affected by LED lights, and the distribution pattern of photosynthate would be changed in the seedlings. The better growth of RB was related with the more photosynthetic pigment content, more stomata number and reasonable photosynthate distribution in cherry tomato seedlings.