中文摘要：

选用不同耐密型品种农大108和郑单958,设置3个种植密度,研究了种植密度对夏玉米基部第3茎节维管束显微结构和茎流速率的影响。结果表明,随种植密度增大,两品种基部茎节的横截面积、大小维管束数目和面积均显著减小,并导致总维管束数目和面积减小。两品种对种植密度的敏感度存在显著差异,农大108比郑单958受高密度影响更大。种植密度增加后,两品种茎流速率及8：00至17：00的总茎流量均显著减小,其中郑单958的降幅小于农大108；茎秆维管束的运输效率均有所提高,郑单958的升高幅度大于农大108。相关分析表明,两品种8：00至17：00的总茎流量与基部茎节的大维管束总面积呈显著正相关。郑单958具有在较高密度下较大幅度提高维管束运输效率的能力,表现出在维管束结构、茎流速率、总茎流量及运输效率上的优势,这可能是其具有较强耐密性,密植后仍能获得高产的原因之一。

英文摘要：

Improving plant density is an important measure to get high yield of summer maize. Two varieties of summer maize with different density tolerances, Zhengdan 958 and Nongda 108, were used to study the effect of plant density on structure of vascular bundles of the third internode and its characteristics of sap flow under three plant densities. The results showed that the cross sectional area of stem and the amount and area of big, small vascular bundles in stalks decreased significantly with the in-crease of plant density, which resulted in the total number and area of vascular bundle decreased. Nongda 108 was more sensitive to plant density than Zhengdan 958. The sap flow rate and amount of sap during 8：00-17：00 decreased significantly with the in-crease of plant density, while the transport efficiency of stalk vascular bundle increased. There was a positive correlation between area of big vascular bundles and amount of sap flow during 8：00-17：00. The structure and function of stalk vascular bundles in Zhengdan 958 were superior to these in Nongda 108, it might be one of the reason that Zhengdan 958 with better density tolerance could get high yield.