中文摘要：

在温室条件下测定并分析不同施氮水平下黄瓜正三叶叶片不同位点的SPAD值的空间分布特征,并对不同位点的SPAD值与叶片含氮量之间的相关性进行分析,探求应用叶绿素计诊断黄瓜氮素营养状况的最佳测试位点.开花期和结果期的研究结果均表明：黄瓜正三叶叶片不同位点的SPAD值存在显著的分布差异,比较不同位点的SPAD值的变异系数,得到叶片边缘的变异系数明显高于主叶脉两侧,而叶尖部三角区域的变异系数明显高于叶片其他任何区域,叶片各位点的SPAD值与叶片含氮量均存在显著的相关关系.初步研究选择离叶尖部相对距离20%与叶边缘之间的叶尖顶三角区域作为黄瓜氮素诊断的最佳位点.

英文摘要：

To determine the best leaf position for nitrogen diagnosis in cucumber with SPAD meter,greenhouse experiments were carried out to study spatial distribution of SPAD value at different position of the 3rd fully expanded cucumber leaf for different nitrogen levels,and the correlation between SPAD value and nitrogen concentration of chlorophyll was also analyzed. The results show that there is remarkable difference for SPAD value at different positions of the 3rd fully expanded leaf in the flowering and fruiting stage. Comparing the coefficients of SPAD value variation,it is found that the variation coefficient of leaf edge is significantly higher than that of the main vein edge,while the variation coefficient of triangular area of leaf tip is significantly higher than those of other leaf areas. There is a significant correlation between SPAD value and leaf nitrogen content. Preliminary study shows that triangular area of leaf tip from the 20% leaf tip to leaf edge is the best position for nitrogen diagnosis.