Effects Of Light Quality On Physiology And Coloration Of Melaleuca Bracteata Cv.‘Revolution Gold’

Melaleuca bracteata cv.‘Revolution Gold’,Myrtleaceae Melaleuca L.The leaves are golden,fragrant and pleasant,with many excellent growth characteristics such as strong vitality.It is one of the most colorful tree species with ornamental value in the world.At the same time,it plays an important role in China’s landscaping and has a broad prospect for development.Light quality has a significant effect on plant physiological growth and biosynthesis of photosynthetic pigments,the cultivation of color-leaved tree species focuses on leaf color regulation.At present,the research on the color change mechanism of Melaleuca bracteata cv.‘Revolution Gold’ leaves and the effect of light quality on them have not been reported.In this study,two-year-old Melaleuca bracteata cv.‘Revolution Gold’ seedlings as experimental materials,Using different light quality irradiation treatments to study the effects of different light qualities(white light,blue light,red light,red / blue light combination 4: 1,3: 2,2: 3)on the physiological indicators of Melaleuca bracteata cv.‘Revolution Gold’ and the Lab parameters of leaves in order to achieve the effect of making Melaleuca bracteata cv.‘Revolution Gold’ leaves show the best leaf color through the adjustment of light quality.The main findings are as follows:(1)By studying the changes in leaf color and related physiological indexes of Melaleuca bracteata cv.‘Revolution Gold’ under different light quality irradiation treatments,and combining the analysis in the Lab color space model that quantifies the leaf color,it is found that the correlation between the indicators indicates that The color change of Melaleuca bracteata cv.‘Revolution Gold’ is mainly determined by the activity of chlorophyll b,total chlorophyll and anthocyanins,and POD.The lower the content of chlorophyll b and total chlorophyll,the lighter the green color of the leaves,the lower the relative content of anthocyanins,and the brighter the leaves.The higher the POD activity,the brighter the leaves and the more pronounced the yellow color.And the main pigment of carotenoid has no significant effect on Lab value.On the other hand,the soluble sugar content indirectly affects the leaf color through the close correlation with the content of important pigments such as photosynthetic pigments and anthocyanins,while flavonoids,soluble protein,CAT activity and MDA content do not contribute much to the color rendering effect of the leaves of Melaleuca bracteata cv.‘Revolution Gold’.(2)With the increase of the light quality treatment time,the POD activity first increased and then decreased.The change in CAT activity also reflected that Melaleuca bracteata cv.‘Revolution Gold’ showed a significant stress response only in the early stage of the test.O n the 75 th day,the MDA content increased significantly,indicat ing that it was too long.The light quality treatment caused a certain damaging effect on Melaleuca bracteata cv.‘Revolution Gold’ which have an adverse effect on its growth.Therefore,the control of light quality cultivation of Melaleuca bracteata cv.‘Revolution Gold’ can ensure the health of seedlings within 60 days.(3)In the Lab model,the 4: 1 light quality treatment of red / blue combination is the most ideal,the leaf color parameters L(86),a(-16),b(72)values from the 60 th to 75 d are the highest,and are significantly higher than other light quality Processing(P <0.05),the data depicts that the leaves under this light quality appear brighter light green and yellow.Therefore,on the 60 th day red / blue 4: 1 combination light quality treatment is an ideal light quality combination and cultivation time.