Impact Of Heavy Metal Stress On Leaf Anatomical Structure Characteristics Of Several Plants

In this paper, local plants:Lonicera maackii Maxim., Comus alba L., Euonymus sacrosancta Koidz., Syringa microphylla Diels and introduced species:Cerasus glandulosa, cultivars:Weigela florida ’Red Prince’, salix integra ’Hakuro Nishilci’, Prunus padus L., three groups in Colorado species, Picea pungens var. glauca, Picea pungens’Kaibab’, Picea pungens ’Misty Blue’ were selected as main object of the study. After two months under the stress of six heavy metals:zinc, copper, lead, mercury, chromium, cadmium, and these plants were paraffin sectioned. Through the application of optical microscopy technique, their leaf anatomical structure’s characteristics of resistance to heavy metal were observed, and9indicators were determined, as leaf thickness, upper epidermis thickness, lower epidermis thickness, palisade tissue thickness, spongy tissue thickness, palisade tissue/spongy tissue, cuticle thickness, leaf tightness and leaf bulk density. Resistance capacity of different species was also compared by a comprehensive evaluation of the membership function. The results showed that:eight kinds of ornamental trees had leaf anatomical structure with a variety of resistance, for they had the cuticle, developed palisade tissue, degraded spongy tissue and other features; under the stress of heavy metals, Pb, Cu, Zn, Cd, Cr and Hg, palisade tissue thickness, spongy tissue thickness, palisade tissue/spongy tissue, the thickness of the upper epidermis and lower epidermis thickness, cuticle thickness and leaf thickness of8ornamental trees changed in varying degrees. In order to adapt to environmental changes, eight kinds of trees changed in anatomical structure, as the palisade parenchyma cell tissue grew thicker, spongy parenchyma cell tissue gradually differed, ratio of palisade tissue/spongy tissue grew bigger, cuticle in creasingly grower thicker. upper epidermis thickness and total leaves thickness of Syringa microphylla had the significant changes, upper epidermis thickness of Cornus alba L. also significantly changed. capabilities of resistance to heavy metal of eight kinds of ornamental trees were as follow:Prunus padus L.> Cerasus glandulosa> Salix integra ’Hakuro Nishilci’> Euonymus sacrosancta> Cornus alba L> Lonicera maackii> Weigela florida> Syringa microphylla; For three groups in Colorado species under heavy metal stress, the thickness of palisade tissue and spongy tissue thickness significantly changed, that is their palisade tissue gradually thickening and spongy tissue gradually thinning with the increase of heavy metal concentration. Three kinds of spruce had changed their structure to adapt to changes in the external environment; resistance of three groups of Colorado species was in line with:Picea pungens ’Misty Blue’> Picea pungens ’Kaibab’> Picea pungens var. glauca., This paper theoretically studied the suitable local conditions, suitable tree in proper land, the priority of ecological function, the principle of landscape value, ecological economy as well as biological diversity to achieve the purpose of purification and beautification of the environment, to provide a theoretical basis for election of the suburb tree species, and also to provide a theoretical basis for the building of eco-garden city.