冬油菜叶片SPAD的时空分布和氮素诊断的叶位选择

在大田试验条件下测定分析不同施氮水平冬油菜关键生育期SPAD值的时空分布特征，并对不同叶位及叶片不同部位SPAD值与叶绿素含量、叶片含氮量、植株全氮含量及籽粒产量之间的相关性进行分析，探求应用SPAD仪诊断油菜氮素营养状况的最佳测试叶位及位点。结果表明，油菜主茎顶部4片完全展开叶SPAD值存在显著空间差异，增加施氮量能显著提高各叶位叶SPAD值，同时减少叶位间的差异；六叶期、蕾薹期以顶4叶（TL4）SPAD值对氮素的敏感性最大，初花期和盛花期则最低。不同部位间，六叶期和初花期以中部SPAD值对施氮量增加的响应最敏感，盛花期则最迟钝，蕾薹期介于顶部和基部之间。综合分析认为，应用SPAD仪监测油菜氮素营养状况的最佳测试叶位和位点为主茎顶4片完全展开叶中部，该部位SPAD值与叶绿素含量、叶片含氮量和植株全氮含量之间的相关性均达到显著或极显著水平，满足氮素营养快速诊断的要求。

Spatial distribution of SPAD value and determination of the suitable leaf for N diagnosis in winter rapeseed

 To determine the best leaf position for nitrogen diagnosis in rapeseed with SPAD meter, field experiments were carried out to study the effect of nitrogen levels on spatial distribution of SPAD value of rapeseed leaves on main stem, and the correlations were analysed between SPAD values and chlorophyll concentration, leaf nitrogen, plant nitrogen and yield respectively. Results indicated remarkable spatial-temporal differences of SPAD values among the first four fully expanded leaves from the top of the main stem. At high nitrogen rates, the SPAD values increased and the spatial-temporal differences decreased. During the six-leaf stage and bolting stage, the fourth leaf from the top (TL4) had the highest N-sensitivity. On the contrary, during the early and full flowering stages, TL1 was the most sensitive. Simultaneously, the SPAD values at different leaf position increased with increasing N supply, and the order of those values from high to low were the top position, the central position and the base position on the TL4. The sensitivity of the central part on the fourth leaf to N was the highest at six-leaf stage and early flowering stage. During the bolting stage, the base position was more sensitive and the roof responded slowly. So the optimal location for N nutritional diagnosis was the central position of the fourth fully expanded leaf from the top of the main stem. There were significant relationships between SPAD values and chlorophyll concentration, leaf nitrogen, plant nitrogen and yield, thus SPAD values was suitable for rapid diagnosis of nitrogen nutrition.