Morphological and Physiological Responses of <i>Morus alba</i> Seedlings under Different Light Qualities

Abstract

Light quality can influence the photosynthetic characteristics, morphology and physiological processes of plants. To investigate the effects of different light qualities (white light, W; red light, R; blue light, B; mixture of red and blue light, RB) of light emitting diodes (LEDs) and white cold fluorescent lamp on the growth and morphology of fruiting mulberry plants (Morus alba L. cv. ‘Longsang No.1’), fruiting mulberry plants were grown under different light qualities: W, R, B and RB of the same photosynthetic photo flux density (PPFD; 100 μmol m-2 s-1) for 20 d. Our results showed that stem length and leaf area of plants grown under R were the highest. However, stem length and leaf area of plants grown under B were lowest. Dry weights (DW), leaf mass per area (LMA), chlorophyll a/b ratio, soluble protein content, sucrose and starch content, and total leaf nitrogen (N) content of plants grown under R were the lowest. Net photosynthetic rate (Pn), stomatal conductance (gs), and actual photochemical efficiency of PSII (ΦPSII) of plants grown under RB were similar to plants grown under W. Net photosynthetic rate (Pn) and ΦPSII of plants grown under R and B were lower than plants grown under W and RB. Antioxidant enzymes activity of plants grown under R, RB and B were higher than plants grown under W. The number of leaf stomata, leaf thickness, palisade tissue length and spongy tissue length were the lowest in plants grown under R. The number of leaf stomata, leaf thickness and palisade tissue length of plants grown under RB and B were higher than plants grown under R. The results of this study indicate that a certain ratio of mixed red and blue LEDs light can reduce adverse effects of monochromatic red and blue LEDs light on fruiting mulberry growth and development.