| Ulmus pumila ‘Zhonghua Jinye’(Ulmaceae,Ulmus L.)is a natural golden leaf mutant of Ulmus pumila. Recently, it was widely applied on landscape for its ornamental value and strong resistance. In order to develop new varities, three different clones selected from Half-sib progeny seed of Ulmus pumila ‘Zhonghua jinye’ were used as materials, and the Ulmus pumila ‘Zhonghua jinye’ and Ulmus pumila were used as controls. In this paper, indicators of growth, photosynthetic characteristics, chlorophyllfluorescence, pigment content, chloroplast ultrastructure and cold resistance were studied The results showed as follows:1. Plants height and stems diameter growth were reached the maximum in July, the monthly growth rate and the total amount of growth of Ulmus pumila were significantly higher than those of Ulmus pumila ‘Zhonghua jinye’ and its clones. In June to August there was no obvious difference among clones. But in September, the height of the clone C was significantly higher than those of clone A and B.2. Net photosynthetic rate of Ulmus pumila and Ulmus pumila ‘Zhonghua jinye’ female showed a double peak curve trend, there is an obvious “midday depression” phenomenon. Clones except A were consistent with their female. Stomatal conductance and transpiration rate change trends were both similar to net photosynthetic’s trend, but Ulmus pumila was significantly higher than those of Ulmus pumila ‘Zhonghua jinye’ and its clones. All the photosynthetic factors of the clone C were higher among the clones. Intercellular CO2 concentration of Ulmus pumila was slightly lower than that of Ulmus pumila ‘Zhonghua jinye’ and its clones, which showed utilization ability of intercellular CO2 of Ulmus pumila was better than Ulmus pumila ‘Zhonghua jinye’ and its clones. The net photosynthetic rate and stomatal conductance of five kinds of materials were extremely significantly or significantly correlated. The diurnal variation trend of maximum fluorescence, initial fluorescence and the maximal photochemical efficiency were similar among Ulmus pumila,Ulmus pumila ‘Zhonghua jinye’ and its clones, but the Ulmus pumila was in the higher level, which indicated photoinhibition of Ulmus pumila ‘Zhonghua jinye’ was more serious.3. Seasonal changes of photosynthesis, stomatal conductance and transpiration rate of Ulmus pumila all reached the maximum in July and generally higher than those of Ulmus pumila ‘Zhonghua jinye’and its clones. However, intercellular CO2 concentration reached the minimum value in August and significantly lower than that of Ulmus pumila ‘Zhonghua jinye’. Compared to the Ulmus pumila,the changes of various indicators of Ulmus pumila ‘Zhonghua jinye’ and its clones were more stable from June to August and showed the same trend with Ulmus pumila after August. The initial fluorescence, maximal fluorescence and maximum photochemical efficiency of Ulmus pumila generally higher than those of Ulmus pumila ‘Zhonghua jinye’ and all the value of those factors of clone A were the lowest. It was concluded that the photoinhibition Ulmus pumila was significantly lower.4. Chlorophyll a, chlorophyll b and carotenoid contents of Ulmus pumila were significantly higher than those of Ulmus pumila ‘Zhonghua jinye’ and its clones in each month; However, there was little difference between those indicators of different clones. From June to August, anthocyanin content of Ulmus pumila was obviously lower than that of Ulmus pumila ‘Zhonghua jinye’ and its clones, while there was no significant differences among them after August. In addition, anthocyanin content of clone A and B was all significantly higher than that of clone C from June to August, which explained that the leaves color of clone A and B was more yellow than that of clone C. The proportion of chlorophyll b content in Ulmus pumila ‘Zhonghua jinye’ and its clones firstly increased and then decreased from June to October, and reached the maximum in August; however, the proportion of chlorophyll a and carotenoid content showed the opposite trend, which reached the minimum value in August. The proportion of the pigment content in Ulmus pumila showed no significantly changes.5. There were obvious differences among chloroplast ultrastructure of Ulmus pumila and Ulmus pumila ‘Zhonghua jinye’ and the clones. Chloroplast thylakoid of Ulmus pumila mostly stacked pile formation of the base granule, in the form of the matrix thylakoids between base granules was dense crosslinked network structure and the number of laminated layers of base granules was also up to a dozen layers to dozens of layers. However, thylakoid of Ulmus pumila ‘Zhonghua jinye’ and its clones were mostly stacked pile fails and the cross-linking structure of the formation of a small amount of base granules was not obvious, the number of base granules stack was also significantly lower than that of Ulmus pumila and the stacked pile level of clones A and B were the worst. In addition, chloroplast structure which existed in different parts also had obvious differences. Thylakoid stacked proportion, stacked number and cross-linked situation were also significantly better than the chloroplasts that existed in the top leaves.6. Soluble sugar content, soluble protein content and proline content of Ulmus pumila and Ulmus pumila ‘Zhonghua jinye’ and its clones all firstly increased and then decreased, and reached the maximum in January. However, the tendency of MDA content was inconsistent. The datas of cold resistance indicating that their cold resistance in January was the highest. Proline content and cold resistance which measured used conductivity method showed a significant negative correlation. In addition, there was a significant negative correlation between starch content and cold resistance. |
PDF Full Text Request