Study On The Mechanism Of The Growth And Development Of Greenhouse Blueberry Under Different LED Supplemental Light

Light is one of the main environmental factors affecting the plant growth and development,which plays an important role in the plant morphological changes,material metabolism,and gene expression.Light emitting diodes,as a new and efficient energy-saving light source,has the characteristics of highly pure light quality,convenient spectral ratios combination and long service life to apply in facility cultivation.Compared with the natural light in the greenhouse,the southern highbush blueberry‘Emerald'were used as material to study the effects of the red/blue?3:1?and red/blue?6:1?,ultraviolet A?UVA?on the plant growth,flowering,fruit quality and leaf senescence.The main results are described as follows:1.The efficiency on the vegetative growth of the blueberry:the plant height,the length and diameter of annual branch increased significantly under the red and blue light treatments.These changes were particularly obvious under the red/blue?6:1?.The diameter of annual branch under the UVA treatment significantly increased,but the crown width and the internode length decreased significantly.2.The effects on photosynthesis and carbon-nitrogen metabolism of the blueberry leaves:the chlorophyll content,the net photosynthetic rate,the soluble sugar content,the carbon-nitrogen ratio of the leaves under the red/blue?3:1?significantly increased.The leaf area,the specific leaf weight,the chlorophyll content,the net photosynthetic rate,the maximum net photosynthetic rate,and the starch content of the leaves under the red/blue?6:1?treatment also remarkably raised,but the intercellular CO₂ concentration decreased.The UVA treatment didn't improve photosynthesis and carbohydrate synthesis of the leaves but significantly reduced the stomatal conductance,the intercellular CO₂ concentration and the transpiration rate.However,UVA promoted the accumulation of the nitrogen content.The red and blue light were more effective than controls for the stronger photosynthesis and more nutrient accumulation of the leaves.3.The effects on the flowering time of the blueberry:according to the statistics of the flowering period,the full-bloom stage under the supplemental light treatment was earlier than that under the control.The flowering time under the red/blue?6:1?treatment was the earliest and had the longest duration.It was found that the photoreceptor genes PHYA,PHYB,CRY2 and the flowering genes CO and FT had the highest expression levels under the red/blue?6:1?treatment,while the photoreceptor gene CRY1 had the highest expression levels under the red/blue?3:1?treatment by the qPCR verification.4.The effects on the fruit quality of the blueberry:the fruit weight,the transverse and longitudinal diameter increased significantly under the red/blue?3:1?and the UVA treatment.The fruit shape index under the red/blue?6:1?treatment decreased significantly.The red and blue light treatment can significantly reduce the titratable acidity content and increase the sugar acid ratio.In addition,the red/blue?3:1?treatment also increased the soluble sugar content,the anthocyanins content,and the soluble solid content.The UVA treatment significantly increased the soluble sugar content and the soluble solid content.The fruit firmness didn't change under the supplemental light treatment.5.The effects on the senescence-related enzyme activity of the blueberry leaves:the supplemental light treatment effectively promoted the antioxidant enzyme activity?SOD,POD and CAT?and the soluble protein content of senescent leaves,with the reduce of the MDA content,which show the leaves under the red/blue?3:1?delayed leaf senescence.In summary,The red/blue?3:1?treatment can enhance the carbon and nitrogen metabolism of the blueberry‘Emerald'leaves,accelerate the flowering process,improve the fruit quality,and delay the leaf senescence.Meanwhile,the effect under the red/blue?3:1?treatment was better than the red/blue?6:1?and the UVA treatment,so this treatment was the best choice for the supplemental light application in facility cultivation.