Effects of combined LED lights with red and blue on photosynthetic characteristics and physiological indexes of‘Tunisia’soft-seed pomegranate

Abstract：【Objective】Pomegranate tree is deciduous, bush or dungarunga, originated in Iran, Afghani⁃stan and other Central Asian regions. Pomegranate is one of the excellent fruit trees with ecological, economic, social benefits, ornamental and health care functions. At present, cultivation techniques of pomegranates have gained some scientific achievements, compared with other fruit trees. However, there was agap in theory study and cultivation techniques, especially in protected cultivation of pomegranate. Withthe development of light emitting diode (LED) light in agriculture, especially, the artificial regulation ofdifferent LED lights was used widely for vegetable production in protected cultivation, and brought greatereconomic benefit, high yield and quality. In order to utilize LED lights for pomegranate industry, four dif⁃ferent combined LED lights with red and blue ones, as supplementary lights, were used for young‘Tunisia’pomegranate trees, so as to obtain the most appropriatethe combined LED lights for the growth ofpromegranate.【Methods】LED was used as supplementary lights for pomegranate cultivar‘Tunisia’, andcombined LED lights were divided into four treatments, including: RB (3∶7), RB (2∶8), RB (7∶3), and RB (8∶2), the natural light as control. Photosynthetic and some physiological characteristics in the leaves,SOD and CAT activity, and MDA content in roots from young pomegranate trees were analyzed with sup⁃plemented four LED light qualities to explore the relationship between different light qualities and pome⁃granate growth.【Results】For leaves, different combined LED light qualities had significant influence onphotosynthetic characteristics during pomegranate growth. RB (2∶8) combined LED light improved obvi⁃ously photosynthetic rate, decreased transpiration rate and intercellular CO2 concentration in young pome⁃granate trees, but RB (3∶7) affected most greatly during the morning and evening of supplementary light;SOD activity with different light treatments followed the decreasing order: RB (3∶7) > RB (2∶8) > RB (7∶3) >RB (8∶2) >control, importantly, its activity with RB (3∶7) and RB (2∶8) were both higher significantly thanthe other two treatments and control; anthocyanin, the soluble sugar and protein contents were all the high⁃est under RB (2∶8) combined LED light. In roots in winter, different LED light qualities had significant in⁃fluence on MDA content, SOD activity and CAT activity. Under RB (2∶8) and RB (3∶7) treatments, SODand CAT activity in roots were the highest while MDA contents were the lowest.【Conclusion】The resultsin the study proved that four combined LED affected beneficially the growth of young pomegranate trees indifferent degrees, and the combined LED lights with blue light more than red light, such as RB (3∶7) andRB (2∶8), improved photosynthetic rate, and stomatal conductance, anthocyanin, the soluble sugar andprotein contents in leaves, SOD activity and CAT activity in roots in winter while decreased MDA contentin roots, transpiration rate and intercellular CO2 concentration in young pomegranate trees, suggesting thatRB (3∶7) and RB (2∶8) were the most appropriate combined LED lights for the growth of pomegranate andmay improve the resistance to environmental stresses for fruit trees.