| At present,China's urbanization process is developing rapidly.There are more and more ecological and environmental problems such as the shortage of urban land resources,the decreasing green area,and the decline of air quality.As a new type of greening mode that does not occupy the urban floor space,roof greening has become one of the effective ways to increase the greening area and improve the greening effect.Due to the particularity of the roof environment and the building load,the types of woody plants that can be applied to the roof greening are limited,and there is no systematic study on the heat resistance and drought resistance of the shrubs in the roof greening in China.Therefore,in order to establish a scientific roof greening plant selection system,comprehensively research and promote the roof greening model suitable for northern China,we must pay attention to the research on the adaptability and ornamental of the roof greening evergreen plants.Due to conditions,the experiment was conducted at the South Campus of Yangling Northwest A&F University.Based on Yangling's climatic conditions,combined with field meteorological factors observation,using the membership function comprehensive evaluation method to evaluate the resistance of Ligustrum×vicaryi Hort,Buxus megistophylla,Nandina domestica,Pittosporum tobira,Photinia×fraseri Dress.It provides reference for screening the roof greening evergreen woody plants with strong resistance.?1?A total of 110 plant species were applied to 13 roof greenings in Xi'an which include 43 families and 83 genera.Eighty-two plant species are selected to use directly in roof greening which include 29 evergreen plants.?2?Observing the dynamic changes of temperature,humidity and wind speed meteorological indicators on the roof and the ground,it is found that the roof is relatively low in temperature,low in humidity and high in wind speed.Observing the temperature changes of the roof matrix and the ground soil,it is found that the average temperature of the roof matrix in summer is 3.6?higher than that of the ground soil,which will affect the growth of the plants.These environmental characteristics of the roof indicate that the plants grown on the roof need to be resistant to harsh environments.?3?Five plants were evaluated by measuring their morphological changes,water content?RWC?,cytoplasmic membrane permeability?EC?,chlorophyll content,malondialdehyde?MDA?content and proline?Pro?content under the simulated drought condition.The order of drought resistance of plants is:Buxus megistophylla>Pittosporum tobira>Photinia×fraseri Dress>Ligustrum×vicaryi Hort>Nandina domestica.?4?The high temperature treatment temperature and cell injury rate of the leaves of the five evergreen plants showed an"S"curve,which passed the significance test and accorded with the Logistic equation.The semi-lethal temperature LT500 from high to low as follows:Buxus megistophylla?62.62??,Pittosporum tobira?62.43??,Ligustrum×vicaryi Hort?61.10??,Photinia×fraseri Dress?58.20??,Nandina domestica?58.09??.Through the determination of cytoplasmic membrane permeability,chlorophyll content,proline content index,the order of heat resistance of plants as follows:Pittosporum tobira>Buxus megistophylla>Photinia×fraseri Dress>Ligustrum×vicaryi Hort>Nandina domestica.In addition,through a comprehensive observation of the plant for one year,combined with the results of various physiological indicators,it shows that the resistance of Buxus megistophylla and Pittosporum tobira were best,followed by Photinia×fraseri Dress,and which of the Golden Leaf virgin and Nantianzhu were worst.The five evergreen shrubs can withstand the drought of more than 30 days and the high temperature environment of42.5?for more than 10 days.It is basically suitable for the application of roof greening in Xi'an,and provides a practical basis for the selection and application of greening evergreen plants in the north. |
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