| Zelkova schneideriana is a native tree species, and a precious rare species in our country, it has high value of landscape ornamental, because of it’s autumn leaf color is variety, and they can grow well in the complex urban environment, because of their high poor resistance and the ability to resist drought. So Zelkova schneideriana has values in high social, economic, landscape and ecological.In order to define the changing mechanism about leaf color of Z. schneideriana, the Z schneideriana whose autumn leaf color is red, green and yellow were the research material in our work. All of the material had been choose in3years and their autumn leaf color is stability. During the expression of leaf color, we developed a technology of ultraviolet spectrophotometer measurement, studied the change characteristic of chlorophyll, carotenoids and anthocyanin content. We developed a technology of anthrone colorimetry, studied the change characteristic of soluble sugar content. We developed a technology of paraffin section and electronic microscopy, studied the leaf structure’s characteristic of the leaf that just began to change color and change color completely. We took the Royal Horticultural Society Color Chart (RHSCC) to match the leaf color and observed the phenological, to study the leaf color’s stability of the three kinds of Z. schneideriana. In the end, we have attained following results and conclusions.1The characteristics of the pigment content change(1) The results showed that there were distinct differences in characteristics of chlorophyll content changes. The green groups’chlorophyll content is the highest, the yellow group is the second, and the red group is the lowest. As the leaf color changes, the3groups’ chlorophyll content has performance to reduce gradually, but the different group has different degradation, and the largest degradation is yellow group, the second is red group, the smallest is green group. The difference of the changing among the three groups’carotenoids content is not obviously, but the green group is slightly higher, the yellow group is second, the red group is the lowest. As the leaf color changes, the carotenoids content have no significant changing, and have been in a relatively stable state. The three groups’ anthocyanin content is significant different, the red group is the highest, which is significantly higher than the other groups. As the leaf color changes, the yellow and green groups’anthocyanin content gradually reduce on the whole, while it show a process of first up and then down in the red group.(2)The three groups’soluble sugar content has same change trend, manifest as rising first and then falling. The red groups’ content is the highest, and there is no significantly difference between the yellow group and the green group.(3) The three groups’Z schneideriana have different correlation between the content of anthocyanin and the content of soluble sugar. In the red group, anthocyanin synthesis and accumulation of soluble sugar has significant positive correlation; But in the yellow and green group, the anthocyanin content and the soluble sugar content has no significant correlation,2. The characteristics of leaf structure change(1) There are many non-glandular hairs presented on the leaf epidermis of three kinds of Z. schneideriana. They are cone-shaped, and have two states of lodging or erect, stomas are all distributed under the skin; the three groups’number of stomata is different per unit area. The green group’s leaf with the most numerous stomata, the red group is the second, and the yellow group is the least.(2) The leaves’morphological characteristic of three kinds of Z. schneideriana is similar.(3)The study shows that the three groups’ quantitative characteristic of the leaf transcent structure is different. The difference of the thickness between the palisade tissue and spongy tissue is much greater than other quantitative characteristic. The thickness of three groups’palisade tissue between104-151μm, and the green group’s leaf is with the thickest palisade tissue, yellow group is the second, the thinnest is red group. The thickness of three groups’sponge tissue is between141.1μm～171.7μm. The spongy tissue of green groups’leaf that began to change color is the thickest, the thickness is171.7μm, and the thinnest is yellow groups’leaves. At the same time, the difference of thickness about palisade tissue and spongy tissue, affect the ratio of palisade tissue thickness and spongy tissue thickness, the organizational structure closely degrees (CTR) and the organizational structure loose degrees (SR). Among them, both of the ratio of palisade tissue thickness and spongy tissue thickness and the CTR of the red groups’leaf is the minimum, significantly less than the green and yellow groups’; the red groups’leaf has the largest SR, the green group is second, and yellow group is the smallest.(4) The chloroplasts had begun to degradation when the leaves began to change color for the3group Z. schneideriana. The grana lamella have disappeared, but the chloroplast envelope is intact. In the process of the leaf change color, the chloroplast degradation gradually, but different color group has different degradation speed, the yellow group chloroplast degradation fastest. After the leaf turn color completely, the red group’s chloroplast envelope is still relatively complete, but the green groups’ chloroplast is obscure, and the yellow groups’chloroplast is fully broken up.3The stability of leaf colorThe results showed that, all the cuttings and grafted seedling colonial plants of3groups Z. schneideriana, their autumn leaf color belong to the same color type with their mother plant, and their phonology time is also similar to mother plant, it showed that the3groups of Z. schneideriana’s leaf color is stable. |
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