小麦叶绿素荧光参数叶位差异及其与植株氮含量的关系

以中蛋白质含量小麦品种矮抗58和高蛋白质含量品种郑麦366为试验材料，2008-2010年连续2个生长季进行了施氮梯度下(0、90、180和270 kg hm^-2)的田间试验。在关键生育时期同步测定叶片荧光参数、叶和茎生物质量及氮含量，建立了基于叶位差的小麦植株氮含量荧光估算模型。结果表明，在小麦旺盛生长的拔节至孕穗期叶绿素荧光参数F_m、F_v、F_v/F_m和F_v/F_o与对应叶片氮含量的相关系数分别为0.557、0.601、0.619和0.633，均达极显著水平(P<0.01)。顶三叶间荧光参数差异较小，随施氮水平提高，顶部第4叶荧光参数与顶三叶间差异逐渐缩小，说明其对增施氮肥反应敏感。顶部第4叶与顶部第1叶间的荧光参数差异(LPD_4-1)可较好拟合小麦拔节期植株氮含量变化，F_v/F_o和F_v/F_m方程决定系数R²分别为0.644 (P<0.001)和0.651 (P<0.001)；顶部第4叶与顶部第2叶间的荧光参数差异(LPD_4-2)方程拟合决定系数有所降低，分别为0.626 (P<0.002)和0.592 (P<0.005)；而顶部第4叶与顶三叶之间的差异(LPD_4-n)与小麦孕穗期植株氮含量间呈显著线性关系，其F_o、F_v和F_m方程决定系数分别为0.726 (P<0.001)、0.791 (P<0.001)和0.784 (P<0.001)。独立数据检验结果表明，小麦拔节期对F_v/F_o和F_v/F_m的LPD_4-1预测精度R²分别为0.844( P<0.001)和0.828 (P<0.001)，相对误差(RE)分别为13.0%和16.7%，而LPD_4-2估算植株氮含量精度有所降低，R²分别为0.793 (P<0.001)和0.813 (P<0.001)，RE分别为16.9%和18.4%。小麦孕穗期对F_v和F_m的LPD_4-n预测方程的R²分别为0.831 (P<0.001)和0.815 (P<0.001)，RE分别为13.2%和16.4%。比较而言，小麦拔节期F_v/F_o的LPD_4-1和孕穗期F_v的LPD_4-n可更好地用于评估不同条件下植株氮含量的变化，为施肥调控提供决策依据。

Difference of Chlorophyll Fluorescence Parameters in Leaves at Different Posi-tions and Its Relationship with Nitrogen Content in Winter Wheat Plant

For diagnosing nitrogen (N) nutrient status in winter wheat plant based on fluorescence parameters of leaves, two cultivars with Aikang 58 (mid-protein content) and Zhengmai 366 (high-protein content) were used in experiments with N application rates of 0, 90, 180, and 270 kg ha^{-1 in 2008–2009 and 2009–2010 growing seasons. The fluorescence parameters were measured in the first, second, third, and fourth leaves from top of plant from jointing to maturity stage. The N contents and biomasses of leaf and culm were determined through destructive sampling and chemica1 assay. The leaf N contents at different 1eaf positions were significantlycorrelated with fluorescence parameters from jointing to booting stage (P < 0.01). The correlation coefficients of N content with F}_m, F_v, F_v/F_m, and F_v/F_o were 0.557, 0.601, 0.619, and 0.633, respectively. The fluorescence parameters of the top three leaves had small differences, which were much higher than those of the fourth leaf from the top. However, the differences reduced gradually with the increase of N application rate. This indicated a sensitive response of leaf position to N application. The differences of F_v/F_o and F_v/F_m between the fourth and the first leaves (LPD_4-1) were significantly correlated with N content in plant (PNC) at jointing stage (R² = 0.644 for F_v/F_o and R² = 0.651 for F_v/F_m); whereas, the differences of F_v/F_o and F_v/F_m between the fourth and the second leaves (LPD_4-2) had less accurate predictions with smaller R² values (R² = 0.626 for F_v/F_o and R² = 0.592 for F_v/F_m). At booting stage, linear equations were obtained for F_o, F_v, and F_m differences (LPD_4-n) between the fourth and the top three leaves (R² = 0.726 for F_o, R² = 0.791 for F_v, and R² = 0.784 for F_m). Using independent datasets to predict PNC at jointing stage with the LPD_4-1 and LPD_4-2 equations based on F_v/F_o and F_v/F_m, the R² values for LPD_4-1 were 0.844 and 0.828 with relative errors of 13.0% and 16.7%, respectively; and the R² values for LPD_4-2 were 0.793 and 0.813 with relative errors of 16.9% and 18.4%, respectively. The result showed that the estimations were reliable. At booting stage, the best prediction of PNC was from the LPD_4-n equation based on F_v and F_m, and R² values were 0.831 and 0.815 with relative errors 13.2% and 16.4%, respectively. In conclusion, the LPD_4-1 equation based on F_v/F_o at jointing stage and the LPD_4-n model based on F_v at booting stage are applicable to estimate PNC of wheat.