关键词: 铁皮石斛, LED光周期, 生理生化, 营养物质, 叶绿素荧光

Abstract: To investigate the effects of different LED red（R）and blue（B）light cycles on the growth and development，photosynthesis，and nutrient accumulation of Dendrobium officinale tissue culture seedlings，tissue culture seedlings of D.officinale were used as experimental material.Based on the previously screened optimal LED red and blue combination light（R∶B=5∶5），five different light cycle treatments were set up［ white light control group（CK），treatment group A（3 h/d），treatment group B（6 h/d），treatment group C（9 h/d） and treatment group D（12 h/d）］.After 120 days of illumination，growth parameters（plant height，number of leaves，leaf length，stem diameter，fresh weight，dry weight），antioxidant parameters［superoxide dismutase（SOD） activity，malondialdehyde（MDA）content，ascorbate peroxidase（APX）activity，peroxidase（POD） activity，catalase（CAT）activity］，photosynthetic pigment parameters（chlorophyll a content，chlorophyll b content，chlorophyll a+b content，chlorophyll a/b，and carotenoid content），chlorophyll fluorescence parameters［PSⅡ maximum photochemical efficiency（Fv/Fm），PSⅡ potential activity（Fv/Fo），actual quantum efficiency（Φ_PSⅡ），electron transport rate（ETR Ⅱ），photochemical quenching coefficient（qP），non⁃photochemical quenching coefficient（qN）］ and nutrient content（amino acids，alkaloids，polysaccharides，flavonoids） were determined.The results showed that the plant height，stem diameter，fresh weight and dry weight of the seedlings reached the peak in treatment D，while the leaf length and number of leaves reached the peak in treatment C. APX，CAT and POD activities peaked in treatment B，SOD activity peaked in treatment C，and the MDA content was the lowest in treatment C. Overall，the nutrient content，photosynthetic pigment indicators and chlorophyll fluorescence parameters of the seedlings were the best in treatment B.There were significant or extremely significant correlations between growth indicators，antioxidant indicators，nutrient indicators and chlorophyll fluorescence parameters and photosynthetic pigment indicators.The principal component analysis results showed that the comprehensive performance of Dendrobium officinale in treatment B was the best in terms of growth indicators，antioxidant indicators，photosynthetic indicators and nutrient accumulation，with a comprehensive score of 3.35.In conclusion，when the red and blue light ratio is 5∶5，LED light exposure for 6 h has the best promoting effect on the growth and development and nutrient accumulation of Dendrobium officinale.

Key words: Dendrobium officinale, LED photoperiod, Physiology and biochemistry, Nutrient, Chlorophyll fluorescence