棉花营养期倒四叶不同位点SPAD值与植株氮营养相关性

为确定棉花叶片SPAD值的适宜测定位点，采用水培试验方法，设0（不施）、1.5 mmol/L（缺乏）、15 mmol/L（适量）3个供氮水平，分4次测定棉花倒四叶17个不同位点的SPAD值，对不同氮素水平条件下棉花倒四叶SPAD值的差异性及其与棉花氮素营养状态的相关关系进行研究。结果表明，棉花倒四叶17个测定位点的SPAD值存在较明显的区域性差异，其中叶尖位置最高，而靠近叶柄的位置最低。不同测定位点的SPAD值与棉花植株氮素营养水平的相关性不同，其中只有靠近叶尖的S2、S3、S15 3个位点的SPAD值同时与倒四叶及地上部氮含量之间有显著相关性，但尚不能确定这些点就是判断棉花氮素营养水平的最佳位点或区域。

The Correlation between Nitrogen Nutrition Status of Cotton Plant and SPAD Value in Different Sites of Inverse Fourth Leaf

A nutrient solution culture experiment with three nitrogen application levels, 0 (no nitrogen), 1.5 (nitrogen deficiency), 15 mmol/L (moderate nitrogen application) was conducted and the SPAD value of 17 different sites in inverse fourth leaf of cotton was measured to investigate the correlation between nitrogen nutrition status of cotton plant and inverse fourth leaf SPAD value under different nitrogen application. The main aim was to determine the most appropriate measurement sites of leaf SPAD value. The results showed that the SPAD value was different in different determine sites, and the highest value was near the tip of leaf, while the value near the petiole was the lowest. The correlation between the nitrogen nutrition and SPAD values was also different in different determine sites, of which only S2, S3 and S15 (near tip of leaf) showed the significant correlation between SPAD value and N concentration in inverse fourth leaf or in cotton shoot. However, the results are not yet certain the most appropriate site to estimate the nitrogen nutrition status of cotton with SPAD value.