| Pyrethrum(Tanacetum cinerariifolium) with white flower is perennial herbs of Compositae, and active substances like pyrethrins used as natural botanical insecticide can be extracted from its head-shaped inflorescence, so it has not only ornamental and medicinal value, but also a broad market prospect. Pyrethrum enjoys cold climate so that it industrialized with extensive adaptability and planting scale in Yunnan in China. Summer is hot in Wuhan, high temperature more than38℃can last about20days some years, which brings a lot of difficulties for preservation, cultivation and spread of good resources of Pyrethrum. Pyrethrum in Wuhan was used as experimental material in this research, and effects of different treatments on the heat resistance through summer of Pyrethrum were studied by growth regulators, shading and trim treatment. It seeks to understand the physiological characteristics of heat resistance of pyrethrum, and find some effective measures to enhance hear resistance through summer of pyrethrum, so more scientific basis can be provided not only for the resistance breeding and resistance selection, but also for the popularization, cultivation and application of Pyrethrum.The test results show that:1. After the treatment of gradient high temperature such as30℃,35℃,40℃,45℃,50℃,55℃,60℃and65℃, high semilethal temperature of Pyrethrum measured was47.91℃.2With the extension of time under high temperature stress, cell membrane permeability, MDA content and soluble sugar content of Pyrethrum leaves increased, while the content of chlorophyll and soluble protein declined. Otherwise, the activity of antioxidant enzymes (SOD, and POD and CAT) also declined.3. Different effects were made by different treatments of concentration chemicals on physiological characteristics of pyrethrum leaves under high temperature stress. Salicylic acid (SAO.1) and brassinolide (EBRO.1) processing more helps maintained stability of membrane system of Pyrethrum; Through the mitigation effect of treatment on chlorophyll decomposition of pyrethrum under high temperature, salicylic acid (SA1) processing best, brassinolide (EBR0.01) followed by, spermidine (SpdO.1) does not play any role; From the point of maintenance of SOD and POD enzyme activity, the effect of best processing concentration on confrontation oxidation enzyme system can be arranged by contribution as follows:salicylic acid (SA0.1)>Spermidine (Spdl)> brassinolide (EBR0.1)> control (CK); In terms of effects of osmotic adjustment, spermidine (Spd) is not as good as salicylic acid (SA) and brassinolide (EBR).4. Pyrethrum sowed in pot seven months ago was treated by three kinds of concentrations of salicylic acid, and the average survival rates through summer was62.2%, followed by46.7%of brassinolide treatment and24.4%of spermidine treatment, especially, Salicylic acid treatment was the best, then was the brassinolide treatment, spermidine treatment was the worst. Application of relatively low concentrations of salicylic acid (SAO.1) was more conducive to improve survival rate of seedlings of pyrethrum through summer; however, applying relatively high concentration of brassinolide (EBR0.1and EBR1) can significantly improve survival rate of seedlings of pyrethrum in summer while applying spermidine concentrations as low as possible can help Pyrethrum to cross summer.5. Effect of different sowing period and different shade degree on survival rate of pyrethrum through summer was clear. The number of seedlings survived eventually in treatments of seedlings sowed in spring+a layer shading, seedlings sowed in spring+two layer shading and seedlings sowed in spring without any shading were respectively10strains,5strains and1strains, Among the treatment of seedlings sowed in spring+two layer shading, only1strains survived, besides, Pyrethrum in the other treatments were all dead, and the death period main set in the repeatedly weather of rain to sunny during June15th to June29th and the continuous high temperature weather during July15th to July31th.6. Prethrum seedling sowed in pot during fall was mowed on June17,2011, leaves were trimmed and the aerial part of plants with8-10CM was kept, and then plants were placed under general management of water and fertilizer outside, the results show that the survival rate of untrimmed plants was higher than trimmed plants in July, August, September and October, and this fully illustrates mowing can not improve the survival rate of Pyrethrum through summer.7. In Wuhan, if the sowing time of Pyrethrum was adjusted for spring, and then salicylic acid (SAO.1) or brassinolide (EBR0.1and EBR1) were applied to spray leaves before the onset of high temperature in summer and a layer of shading was adopted in summer, the survival rate of Pyrethrum in summer definitely can be improved significantly. In addition. management should be enhanced when it meet the repeatedly weather of rain to sunny and the continuous high temperature weather... |
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