Study On The Formation And Regulation Of Leaf Color From Acer Rubrum L.

Landscaping has been recognized as "eternal sunrise industry" worldwide, while cult ivat ing color-leaf plants is an important aspect in quality improving of landscaping there is a critical shortage of large color-leaf trees in China. Red maple(Acer rubrum L.) is a fast-growing tree of medium height that is indigenous to the eastern United States and southern Canada. It has high ornamental value for its beautiful treelike and gorgeous leaf color, many cultivars have been selected, of which almost all are selections for leaf color characteristics, in order to make more widespread in China since the early 2000 s. Though red maple has been spread fast and well received in many cities but its color performance in autumn leaf is more beautiful than expected, especially in southern China, such as Chongqing. It is an urgent problem in widespread of red maple in southern China landscaping that how to regulating leaf color expression in a way that is easy to operate. In this study, two cultivars of red maple(Acer × freemanii ?Jeffersred‘ and Acer rubrum ?Brandywine‘) were selected to study its mechanism of leaf color changing in autumn by measure photosynthetic pigments, anthocyanin, and osmotic adjustment substance concentrations in leaves, and investigate regulatory mechanism to leaf color by artificial int erferences which is spraying sucrose solutions(0.2 mol/L) to red maple leaves or girdling on main branches with glass fiber(width about 2 cm). The study that provide theoretical support for widespread introduction and landscape application in China, and provide new ideas for leaf color regulation, is aimed at finding a simple and easy to operate way for regulating of leaf color performance. The main results are as follows:1. The results indicate that during leaf color changing period the changing range of the leaf color L and b from lab hue cube was relatively narrow, while the leaf color parameter a had an obvious change. The content of photosynthetic pigments showed a downtrend as the leaf color changing, while the contents of anthocyanin, flavonoid, soluble sugar and soluble protein showed an uptrend. And the activity of peroxide enzyme showed a unimodal curve and the maximum appeared at the beginning of color changing period. Furthermore relative analyses indicated that the value a of leaf color had an extremely obvious negative correlation with the content of the photosynthetic pigment, and an extremely obvious positive correlation with the contents of anthocyanin and soluble sugar. The leaf color parameter b had an obvious positive correlat ion with the content of flavonoid. And there were not any obvious correlations between the parameter L and the relative physiological indexes.The major factors impact red maple leaves color changing are the contents of photosynthetic pigment, anthocyanin and soluble sugar in leaves. The content of the flavonoid had few effects on the leaf color changing. And the content of the soluble protein and the activity of peroxide enzyme(POD) had no direct relations with the leaf color changing.2. Girdling signif icantly improve the value a parameter of red maple leaves from upper branches(S2) and reduce its lightness value L and b. Shades order of red in red maple leaves is S2> C1(lower part of the control)> C2(control upper part)> S1(the lower part of the band)(from dark and light, the same as lightness and yellow color), lightness order is S1 >C1 >C2 >S2, yellow color order is S1 >C1 >C2 >S2. Concentrations of chlorophyll a, chlorophyll b, and total chlorophyll were signif icantly increased while carotenoid signif icantly reduced in girdling branches compared with the control, girdling also significantly increased the accumulating of anthocyanin in red maple leaves from upper branches. The contents of mineral elements that is lower in upper branches than leaves of lower branches were while the absorption and transportation of which were not significantly influenced by the glass fiber. Activit ies of phenylalanine ammonia lyase(PAL) and polyphenol oxidase(PPO) made some differences on anthocyanin synthesis in red maple leaves. There is a degree of correlation between soluble sugar concentration and leaf color lab hue cube. Changes on the red maple leaf color is the external manifestation of the internal phys iological activit ies, girdling affects the duration and quality of red leaves of red maple by interfering the synthesis of photosynthetic pigments and anthocyanin in it.3. Spraying sugar solutions on red maple leaves reduced the concentrations of photosynthesis pigments and p H value and increased the concentrations of anthocyanin, soluble protein and soluble sugar in the leaf. With the decrease of the accumulation in photosynthet ic pigments and the increase of anthocyanin concentrations and its stability for red coloration spraying sugar solutions affected the leaf color of red maple indirectly. The changing trend of leaf color lab hue cube was consistently with pigments synthesis inside the red maple which indicated that lab hue cube is a good instrument in quant ification of leaf color. The instrument needs to be amended when the color is dark otherwise there would be some errors.This paper is researching on the expression and artificial regulat ion of red maple leaf color by studying the correlations between internal physiological activator and external leaf color expression. The results show that chlorophyll and anthocyanin are primary substances that effect red maple leaf color, among them chlorophyll plays a more important role. This might be a theory basement for studies on leaf color of red maple. We also found that girdling makes leaves upon the girdle turn red earlier and more accordance which brings a new direction for artificial regulation in red maple landscaping and provides a reference for researches on other color-leaf plants.