Abstract

Red (660±30 nm) and far-red (730±30 nm) LED light sources were combined in different proportions to yield a design with four R:FR ratio treatments (0.5, 2.5, 4.5 and 6.5). Chrysanthemum plants irradiated with natural light served as the control (R:FR=1.02). The chlorophyll a (Chla) content and SPAD value of chrysanthemum leaves were highest for an R:FR ratio of 2.5 and lowest for an R:FR ratio of 6.5. The chlorophyll b (Chlb) and carotenoid content were highest for an R:FR ratio of 0.5 and lowest for R:FR ratios of 6.5 and 2.5, respectively. The superoxide dismutase (SOD), peroxidase (POD) activity and soluble protein content of the chrysanthemum leaves were highest for an R:FR ratio of 2.5, whereas the catalase (CAT) activity was highest for an R:FR ratio of 4.5. The SOD, POD, CAT activity and soluble protein content were found to be lowest for an R:FR ratio of 0.5. The malondialdehyde (MDA) content of the chrysanthemum leaves was highest for an R:FR ratio of 0.5 and lowest for an R:FR ratio of 2.5. These results implied that the antioxidant enzyme activity and the anti-senescence ability of the chrysanthemum leaves were highest for an R:FR ratio of 2.5 and lowest for an R:FR ratio of 0.5.

Key words: Chrysanthemum, R:FR, senescence, chlorophyll, antioxidant enzyme.