棉花叶片不同位点SPAD值与植株氮营养相关性研究

为了确定最能代表棉花氮素营养水平的叶片SPAD值测定位点，采用水培试验方法，设7个供氮水平，分3次测定棉花6片主叶（倒1叶至倒6叶）17个不同位点的SPAD值，对棉花不同叶位及同一叶片不同测定位点SPAD值与棉株氮素营养水平的相关关系进行研究。结果表明，倒4叶SPAD值与棉株地上部氮含量的相关性最好，相关系数为0.6524，达到了显著水平，可认定倒4叶为棉花的功能叶。而棉花倒4叶17个测定位点中，叶片上缘位置SPAD值与地上部氮含量的相关性较靠近叶柄的部位更好，其中S3位点即叶尖位置的相关系数最高，为0.4597，达极显著水平。可以初步确定棉花倒4叶叶尖位置为测定SPAD值以判断棉花氮素营养水平的最佳位点。

The Correlation Between Nitrogen Nutrition of Cotton Plant and SPAD Value in Different Sites of Cotton Leaf

An nutrient solution experiment with seven nitrogen application levels, and measured the SPAD value of 17 sites in different cotton leaf was conducted to investigate the correlation between nitrogen nutrition status of cotton plant and 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 leaf of the reverse 4th from the apex of the main stem was the best measuring leaf because of there was significant correlation between the nitrogen nutrition and SPAD values of the 4th leaf in all leaves. The correlation between the nitrogen nutrition and SPAD values was also different in different determine sites of inverse fourth leaf, which S3 (tip position tip leaf) showed the best significant correlation between SPAD and N concentration of cotton shoot. The results suggested that, the location of near tip of leaf in inverse fourth leaf was the most appropriate site to estimate the nitrogen nutrition status of cotton with SPAD value.