| Echinacea purpurea is one of a few medicinal plants so far we found that have both immunity activity and anti-inflammatory effect. It has a very high medicinal value and great prospects for development. Echinacea purpurea polyploid obtained by biotechnology methods not only have stable biological characteristic, but also have higher biomass and medicinal active component content than diploids. These good traits is of great significance to cultivate Echinacea purpurea with high yield and high quality. As we know, the photosynthesis is an important physiological metabolic process for plants to absorb CO2 and H2 O and accumulate organic matter. In the research, we compared the differences of photosynthetic efficiency between different ploids of Echinacea purpurea and studied the effect of ploid change on photosynthesis efficiency of Echinacea purpurea by comparing differences in leaf morphology and structure of different ploidy of Echinacea purpurea. In my study, we use diploid and tetraploid Echinacea purpurea as experimental material, carried on a comparative study of the photosynthetic efficiency, leaf morphological characteristics, leaf microstructure and ultrastructure, mesophyll cells morphological characteristics and chloroplast dividing frequency of tetraploid and diploid Echinacea purpurea adopting the mehods of light saturation curve determination, light determination of chlorophyll content, leaf phenotype analysis, semi-thin sectioning, ultrathin sectioning, cell segregation and laser confocal microscope. Discussed the influence of increased gene dose on the photosynthetic efficiency and the leaf morphology and structure of Echinacea purpurea, and analyzed the effect of ploidy change on photosynthetic efficiency from the aspect of cytology and morphology, main results are as follows:1. Tetraploid Echinacea purpurea has stronger photosynthetic efficiency diploids. The research about light saturation effect curve of different development ploids of Echinacea purpurea showed that the maximum net photosynthetic rate of tetraploid Echinacea purpurea is 51.84%,36.94%,8.50% higher than the diploid at vegetative stage, bud stage, flowering stage, respectively. Corresponding with that the chlorophyll content of Tetraploid Echinacea purpurea leaf was higher than diploid in different growth period. The total chlorophyll content of tetraploid Echinacea purpurea is 29.63%, 11.51% and 24.78% higher than the diploid in vegetative stage, bud stage and flowering stage respectively.2. The research of mature leaf phenotype measurement about diploid and tetraploid Echinacea purpurea in different development periods has shown that leaf length and width of tetraploid Echinacea purpurea are greater than the diploid. Leaf length of the tetraploid Echinacea purpurea increased for about 3.6%, 8.8%, 2.9% at the vegetative stage, bud stage and flowering stage compared with the diploid, respectively. Leaf width of the tetraploid Echinacea purpurea increased for about 25.5%, 37.4%, 10.8% in vegetative stage, bud stage and flowering stage compared with the diploid, respectively. The results show that tetraploid leaf photosynthesis area increase is beneficial to using light energy.3. Comparing the microstructure of diploid and tetraploid Echinacea purpurea mature leaves through thin section, found that the blade thickness, palisade tissue thickness, sponge tissue thickness of the tetraploids were increased by 30.37%, 19.98%, 38.8% compared with the diploids respectively.Tetraploid leaves have developed palisade tissue and increased cell layers. Tetraploid palisade tissue and spongy tissue cells area is increased by 23.07% and 23.07% relative to its diploid respectively. Chloroplast number per cell in Tetraploid palisade tissue and spongy tissue cells incrreased by 59.70% and 59.70% respectively relative to its diploids. Comparative study of Ultrastructure about diploid and tetraploid mature leaves shows that the tetraploid Echinacea purpurea chloroplast have larger volume, less number of starch grains, more granas with regular shape, grana lamella fold tightly and more developed.Chloroplast long, chloroplast wide, grana number per chloroplast and grana thickness increased by 15.63%, 24.32%, 27.27% and 15.63% in Tetraploid Echinacea purpurea chloroplasts respectively. Changes of blade shape and structure, microstructure of the chloroplast in Tetraploid Echinacea purpurea is advantageous to photosynthetic ability enhancement.4. Segregation statistics of different development phase of the Echinacea purpurea blade found that the chloroplast division period is coordinate with cell volume expansion period in mesophyll cells. The expansion of cell volume is begin from leaf of 1cm in length of tetraploid Echinacea purpurea while it begin later in leaf of 2cm in length of diploid Echinacea purpurea. But the chloroplast number of diploid and tetraploid Echinacea purpurea are both rapid increased in leaf of 3cm in length. Therefore, our results support that the continuous increasing of chloroplast number in tetraploid mesophyll may be through the continuous increase of mesophyll cell volume to provides ample space for the increased number of chloroplast in mesophyll cell.5. Study of Echinacea purpurea leaf ultrastructure in different development stages found that the divisive chloroplast in diploid and tetraploid Echinacea purpurea can be divided into two types: plasmid and young chloroplast. Study showed that not only the division frequency of chloroplast in tetraploid Echinacea purpurea is higher than in diploid Echinacea purpurea, but also the chloroplast showed continuing division until the leave length reach to 6cm in tetraploid Echinacea purpurea. Howerver, the chloroplasts were no longer be divided when the leave length reach up to 4 cm in the diploids. State that the increased number of chloroplast in tetraploid mesophyll cells is result from the joint action of the increased division frequency of chloroplast and the continuous chloroplast division period.Comprehensive analysis of the results above showed that in different development periods, the tetraploid Echinacea purpurea photosynthesis efficiency were higher than that of diploid, provides the biological basis for Echinacea purpurea biomass increasing. In addition, ploidy change effect leaf photosynthetic efficiency by influencing the chloroplast ultrastructure, chloroplast divisions frequency and mesophyll cell expansion rate to change the morphogenesis of leaf in Echinacea purpurea. |
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