Abstract: In this paper, Rhododendron simsii 'Pinghua' was used to study effects of different light quality (white, red, blue) and different daminozide (B₉) concentrations (0, 300, 600, 900 mg·L^-1) on its flowering time, flower diameter, flower formation rate by measuring photosynthetic characters in leaves and content of soluble sugar and soluble protein and the activity of superoxide dismutase (SOD) in petals during flowering process. Our main purpose was to improve omanmental values of the variety and provide a scientific basis and technical support for the commercial production of R. simsii. The results indicated that: in comparison with control, all the treatments prolonged the flowering duration, enhanced the photosynthetic characteristics, and delayed the senescence of petals. Combination of blue light or red light with B₉ in a given concentration was more effective than using any alone treatment in improving omanmental values. But the combination caused antagonisetic effect when the B₉ concentration was too high. The treatment of blue light+300 mg·L^-1 B₉ increased the photosynthetic rate, accumulated the content of soluble sugar and anthocyanin in petals, and improved the flowering probability and flower diameter. The treatment of red light +600 mg·L^-1 B₉ increased the chlorophyll b in leaves and the soluble protein in petals, delayed the decrease of the SOD activity in petals effectively, and gained the longest flowering duration. Integrated all indices, the treatments of blue light+300 mg·L^-1 B₉ and red light+600 mg·L^-1 B₉ were better than the other treatments and improved the quality of flowers effectively.

Key words: Rhododendron simsii, light quality, flowering time, ornamental quality