<正>植物多样性是高速公路绿地系统生态功能的基础和绿地景观多样化的前提，也是其园林绿化水平的重要指标。笔者将植物多样性原理用于宁淮高速公路环境景观建设，运用α-多样性测度的方法，评价了高速公路互通区植物群落的乔木层和灌木层多样性状况。结果表明：宁淮高速公路植物种类较为丰富；被评价的5个互通区乔木层物种数少于灌木层，乔木层物种丰富度存在较大差异，灌木层的物种多样性指数Simpson和Shannon-wiener变化幅度比乔木层大，物种丰富度等多样性指数较高，表现了很高的多样性和一致性；与同纬度自然植物群落相比，植物多样性较好，其平均值比较接近于落叶阔叶林性质。

Top buds of one-year-aged seedlings of Chinese buckeye (Aesculus chinensis Bunge) and red buckeye (A. pavia L.)were placed in different cold stress conditions, and the ultrastructural changes of these top bud cells were compared under the transmission electron microscope. The results showed that the lethal temperature and duration time of top bud in Chinese buckeye was-18℃ within 72h, -30℃ within 24～72h, and-70℃ within 24 h. The ultra structure of top buds in Chinese buckeye at the lethal condition was shown as fol lows: most of cells were degraded and vacuolated. The cytoplasm was disintegrated. Although a few of cells were not disintegrated, their nuclear membrane could not be seen clearly. The lethal temperature and duration time of top buds in red buckeye was--18C within 168h.-30℃ within 168h, and-70℃ within 24 h. The ultra-structure of top buds in red buckeye at the lethal condition was shown as follows: The plasmolization was found in cells. Cell structure was blurred. The cytoplasm was disintegrated. Cell nucleus was condensed and many black particles were found in plasma membrane. It could be found from the comparison of ultra-structure in two species that the cold-resistance of Red buckeye was better than that of Chinese buckeye.