| The color of leaves of many colored-leaf plants may be dim, even appears phenomenon of regeneration in condition of strong light and high temperature in summer, especially in condition of hot and humid environment in southern. Because of this, the colored-leaf plants will lose its landscape value, and its production and sale will be had great influence. It has important practical significance, theoretical value and practical significance that a simple and accurate method has been used to solve the problem of discoloration in colored-leaf plants in summer through foliage application of KH2PO4and sucrose solution, and discuss the effects on plants’photosynthetic characteristics and physiological, ecological index by the two materials in leaf pigment formation progress. Potted three-years-old red-leaf peach was tested in this research.0.2%KH2PO4,0.3%KH2PO4,0.5%KH2PO4,0.3%sucrose,0.5%sucrose,0.8%sucrose solutions were applied on foliage of red-leaf peach in early summer (June). Changes of important physiological, photosynthetic characteristics and kinds of pigments content were compared and analyzed systematically after applying different kinds and concentrations of nutrient solution on red-leaf peach in summer. In the next step, open cultured three-years-old purple-leaf plum was selected as test materials (three-years-old green-leaf plum as comparison).0.3%KH2PO4,0.5%sucrose solutions which had better result were taken to verify universality of experiment results and studied further. Effects of physiological, photosynthetic, fluorescence characteristics and kinds of pigments content were compared and analyzed systematically after applying KH2PO4and sucrose solution on purple-leaf plum and green-leaf plum in summer. The results show that:1. Effects of foliage application of KH2PO4and sucrose solution on changes of pigments and photosynthetic characteristics in leaves of red-leaf peach in summer.The results show that, foliage application of both of different concentration of KH2PO4 and sucrose solution can significantly promote accumulation of anthocyanin (Ant.), improve the ratio of Ant. and chlorophyll (Ant./Chl.), and increase appreciation effect. Meanwhile, soluble sugar and starch content, activity of phenylalanine ammonia lyase (PAL), and basic photosynthetic index, including net photosynthetic rate (Pn), water use efficiency (WUE), apparent quantum yield (AQY) and carboxylation efficiency (CE) have been increased more or less in foliage. Photosynthetic accumulation amount also has been increased, such as daily integral value of net photosynthetic rate (DIV of Pn), daily integral value of water use efficiency (DIV of WUE), etc. Since the range of available light energy has been increased, when appreciation effect has been increased after foliage application nutrient solution in summer, the Pn has been raised and operation of assimilation products and accumulation of dry matter also have been promoted correspondingly. Analysis suggests that KH2PO4and sucrose may improve anthocyanin content through two sides. The one side is to increase photosynthetic rate, improve soluble sugar and starch content, promote synthesis and transportation of sugar, so as to provide carbon skeleton for synthesis of anthocyanin. The other side is to significantly raise activity of PAL and other enzymes. Combined with appreciation effect and important physiological ecology index of red-leaf peach, the most significant effect is foliage application of0.5%sucrose, the total effect is0.5%sucrose solution>0.3%KH2PO4solution>0.3%sucrose solution>0.2%KH2PO4solution>0.8%sucrose solution>0.5%KH2PO4solution.2. Effects of foliage application of KH2PO4and sucrose solution on changes of pigments and photosynthetic characteristics in leaves of purple-leaf plum in summer.The results show that, foliage application of both0.3%KH2PO4and0.5%sucrose solution can significantly promote accumulation of anthocyanin, improve the ratio of Ant and chlorophyll, and increase appreciation effect. Meanwhile, soluble sugar and starch content, activity of PAL and peroxidase (POD) have been increased. However, malondialdehyde (MDA) content and cell membrane permeability have been decreased. Basic photosynthetic index, including Pn, WUE, AQY and CE have been increased more or less in foliage, so as the photosynthetic accumulation amount such as DIV of Pn, DIV of WUE, and so on. It has been found that at noon about13:00, maximal photochemical efficiency of PS II (Fνy/Fm) is significantly increased, actual photochemical efficiency (ΦPS Ⅱ)and non-photochemical quench (qN) are raised after analyzing chlorophyll fluorescence parameters. So after foliage application of nutrient solution, the harm caused by photoinhibition to photosystem has been reduced through increasing of ΦPS Ⅱ and consuming excess light energy to defense photodamage. It is found in this research that after foliage application of KH2PO4and sucrose solution, increasing amount of Pn, DIV of Pn, DIV of WUE, soluble sugar and starch content in leaves of green-leaf plum are more than that of purple-leaf plum. To promote coloring and growing, foliage application of0.3%KH2PO4solution has more remarkable effects.3. Comparison to effects of foliage application of0.3%KH2PO4and0.5%sucrose solution changes of pigments and major photo synthetic physiological ecology characteristics in leaves of Red-leaf peach and purple-leaf plum in summer.After analyzing some index including Ant., Car., Chl., Ant./Chl., PAL, DIV of Pn, DIV of WUE, soluble sugar and starch content in leaves of red-leaf peach and purple-leaf plum by foliage application of0.3%KH2PO4and0.5%sucrose solution, it is known that, leaf coloration-emerging and improvement of photosynthetic capacity can be promoted by foliage application of0.3%KH2PO4and0.5%sucrose solution. However, promoting leaf coloration-emerging has better results in leaves of red-leaf peach by foliage application of0.5%sucrose solution, and in leaves of purple-leaf plum by foliage application of0.3%KH2PO4solution. Photosynthetic indexes containing DIV of Pn, AQY, CE, etc, have better results in leaves of red-leaf peach and purple-leaf plum by foliage application of0.3%KH2PO4solution. |
