Abstract:

In order to understand the adaptation strategy of plants to the special habitat of urban expressway, the leaf anatomical structure of five shrubs, which are Allamanda schottii, Ficus microcarpa ‘Golden Leaves’, Duranta erecta ‘Golden Leaves’, Ixora chinensis and Fagraea ceilanica, growing in road dividing strip of Nanning City was studied using isolation and paraffin section. By measuring or calculating 12 quantitative indexes such as leaf thickness, main vein thickness and stomatal density, the adaptive characteristics of various plant leaves to special environment were further analyzed by using multiple comparison and principal component analysis. The results showed that: (1) all five plants had heterophyllous leaves, which were composed of epidermis, mesophyll and veins, and stomata were only distributed in the lower epidermis. (2) The stomatal density, leaf and sponge tissue thickness were significantly different among all plants, and other indicators were also different in different degrees, indicating that the adaptation strategies of different plants were different: the six maxima and two sub-maxima of Fagraea ceilanica showed their remarkable adaptability. However, Duranta erecta ‘Golden Leaves’, which had eight minima, responded to unfavorable conditions with the maximum stomatal density and tight mesophyll tissue. The unique “compound epidermis” form of Ficus microcarpa ‘Golden Leaves’ made the upper and lower epidermis reach the maximum, and at the same time reduces the consumption with the minimum stomatal density. The thickest cuticle in Allamanda schottii was used to prevent excessive transpiration on the leaves, while the thicker cuticle and greater mesophyll compactness were used to reduce its own consumption in Ixora chinensis. (3) The comprehensive order of environmental adaptability of five greening shrubs to the road dividing strip were as follows: Fagraea ceilanica> Ixora chinensis> Ficus microcarpa ‘Golden Leaves’> Allamanda schottii> Duranta erecta ‘Golden Leaves’.

Key words: leaf structure, ecological adaptability, greening shrubs, road dividing strip, Nanning City