北方地区不同黄瓜品种氮素吸收与利用效率的差异

【目的】研究北方地区栽培黄瓜品种氮素吸收利用的差异，为氮高效黄瓜品种筛选提供参考依据。【方法】选用华北型黄瓜品种为材料，采用二因素裂区设计，以氮素营养水平为主区，设低氮素（3.5 mmol·L^-1）和高氮素（11.0 mmol·L^-1）两个水平；以品种为副区，设32个水平，进行水培试验。测定含氮量、氮素吸收与利用效率，并划分品种营养效率类型。【结果】供试黄瓜品种在两个氮素水平下氮素吸收效率和氮素利用效率的相关指标均存在显著差异。两氮素水平下的植株干物重（CV N3.5 21.49%和CV N11 18.51%）、氮素吸收效率（CV N3.5 19.90%和CV N11 19.94%）和氮素利用指数（CV _N3.5 25.49%和CV _N11 19.25%）均有较大的品种差异。干物重与茎叶氮素累积量和氮素利用指数极显著相关（P<0.01），相关系数分别为r_N3.5 0.933**和r_N11 0.925**，r_N3.5 0.964**和r_N11 0.941**。氮素吸收效率与茎叶氮素累积量和氮素利用指数极显著正相关，相关系数分别为r_N3.5 0.986**和r_N11 0.963**，r_N3.5 0.809**和r_N11 0.768**；氮素利用效率与茎叶含氮量极显著负相关，相关系数分别为r_N3.5 -0.909**和r_N11 -0.886**。以两个氮素水平下的植株干物重平均值为标准，对黄瓜品种的氮素营养效率进行分类，干物重大于平均值的为高效型，小于平均值的为低效型，可将32个华北型黄瓜品种分成4种氮素营养类型，即双高效型、高氮高效型、低氮高效型和双低效型。其中低氮高效型品种数量最少，占供试品种的15.6%。通径分析显示，氮素吸收效率在两氮素水平下对氮效率（植株干物重）的贡献率远大于利用效率，二者对氮效率的通径系数分别为q_N3.5 1.069和q_N11 0.931，q_N3.5 0.347和q_N11 0.361。【结论】黄瓜苗期的氮效率存在品种差异。植株干物重可作为同一供氮水平下苗期氮效率评价的首选指标，茎叶氮素累积量、茎叶含氮量和氮素利用指数可作为氮效率选择的次级指标。植株氮素吸收效率是品种苗期氮效率高的主要因素。水培试验可有效地反应不同黄瓜品种苗期氮素营养效率差异，为黄瓜品种苗期氮素营养效率的批量筛选和快速鉴别提供了可能。

Variation in Nitrogen Uptake and Utilization Efficiency of Different Cucumber Varieties in Northern China

【Objective】The objective of the experiment was to probe the variety variation of nitrogen uptake and utilization efficiency among cucumber genotypes in northern China for providing reference for nitrogen efficient varieties screening.【Method】 Cucumber varieties of North China ecotype was used as the test materials in a hydroponic experiment, the split plot design was employed with main plot of nitrogen nutrition levels (3.5 mmol·L^-1 and 11.0 mmol·L^-1), sub-plot of cucumber varieties. Content, assimilate and utilization efficiency of nitrogen was measured, nutrition efficiency type was divided. 【Result】 The indicators related to nitrogen uptake and utilization efficiency at two nitrogen levels were significantly different among cucumber varieties. Plant dry weight, nitrogen uptake efficiency and nitrogen utilization index showed a significant varietal variation under two nitrogen levels, the coefficient of variation were CV _N3.5 21.49 % and CV _N11 18.51 %, CV _N3.5 19.90 % and CV _N11 19.94%, CV _N3.5 25.49 % and CV _N11 19.25 %, respectively. Plant dry weight was very significantly correlated to stem-leaf N accumulation, plant N utilization indexes (P< 0.01), and correlation coefficient were r_N3.5 0.933^** and r_N11 0.925^**, _N3.5 0.964^** and r_N11 0.941^**, respectively. Nitrogen uptake was significantly positively correlated with stem-leaf N accumulation, plant N utilization index, and the correlation coefficients were r_N3.5 0.986^** and r_N11 0.963^** , r_N3.5 0.809^** and r_N11 0.768^**, respectively; Nitrogen utilization efficiency was significantly negatively correlated with stem-leaf nitrogen content, and the correlation coefficients were r_N3.5 -0.909^** and r_N11 -0.886^**. Pant dry weight average as a standard under two nitrogen levels to classify nitrogen nutrition efficiency of cucumber varieties, the plant dry weight of efficient type was more than the average, and that of the inefficient type was less than the average. Varieties were classified into four nitrogen types, such as efficient-efficient, efficient-inefficient, inefficient-efficient, and inefficient-inefficient types. The least was inefficient-efficient type, which was 15.6% of these varieties. The path coefficient analysis revealed that nitrogen use efficiency was dominated by nitrogen uptake efficiency at two nitrogen levels, the path coefficient with nitrogen use efficient was q_N3.5 1.069 and q_N11 0.931, q_N3.5 0.347 and q_N11 0.361, respectively. 【Conclusion】 Nitrogen use efficiency of seedlings of different cucumber varieties showed a significant varietal variation. Plant dry weight can be used as the first index for evaluation difference in nitrogen use efficiency of seedlings at the same N level, stem-leaf nitrogen accumulation, stem-leaf N content and nitrogen utilization index can be used as the secondary indexes. Nitrogen uptake efficiency is a major factor for high N use efficiency of seedling. A hydroponic experiment can effectively reflect nitrogen nutrition efficiency variation of cucumber seedlings of different varieties, and it provides a possibility for massive screening of nitrogen use efficiency of cucumber seedlings and rapid identification.