| Summary: | This study investigated the effects of nitrogen form on root activity and nitrogen uptake kinetics of <i>Camellia oleifera</i> Abel. seedlings, providing a scientific basis for improving nitrogen use efficiency and scientific fertilization in <i>C. oleifera</i> production. Taking one-year-old <i>C. oleifera</i> cultivar ‘Xianglin 27’ seedlings as subjects, 8 mmol·L<sup>−1</sup> of nitrogen in varied forms (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow><mi>NO</mi></mrow><mn>3</mn><mo>−</mo></msubsup></semantics></math></inline-formula>:<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow><mi>NH</mi></mrow><mn>4</mn><mo>+</mo></msubsup></semantics></math></inline-formula> = 0:0, 10:0, 7:3, 5:5, 3:7, 0:10) was applied in this study as the treatment conditions to investigate the effects of different nitrogen forms on root activity and nitrogen uptake kinetics in <i>C. oleifera</i> seedlings. Comparing the performance of nutrient solutions with different <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow><mi>NO</mi></mrow><mn>3</mn><mo>−</mo></msubsup></semantics></math></inline-formula>:<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow><mi>NH</mi></mrow><mn>4</mn><mo>+</mo></msubsup></semantics></math></inline-formula> ratios, the results showed that a mixed nitrogen source improved the root activity of <i>C. oleifera</i> seedlings based on total absorption area, active absorption area, active absorption area ratio, specific surface area, and active specific surface area. When <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow><mi>NO</mi></mrow><mn>3</mn><mo>−</mo></msubsup></semantics></math></inline-formula>:<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow><mi>NH</mi></mrow><mn>4</mn><mo>+</mo></msubsup></semantics></math></inline-formula> = 5:5, the total absorption area and active absorption area of the seedling roots reached the maximum. The results of uptake kinetic parameters showed that Vmax <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow><mi>NH</mi></mrow><mn>4</mn><mo>+</mo></msubsup></semantics></math></inline-formula> > Vmax <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow><mi>NO</mi></mrow><mn>3</mn><mo>−</mo></msubsup></semantics></math></inline-formula> and Km <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow><mi>NO</mi></mrow><mn>3</mn><mo>−</mo></msubsup></semantics></math></inline-formula> > Km <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mrow><mi>NH</mi></mrow><mn>4</mn><mo>+</mo></msubsup></semantics></math></inline-formula>, indicating that the uptake potential of ammonium–nitrogen by <i>C. oleifera</i> seedlings is greater than that of nitrate–nitrogen. The conclusion was that compared to either ammonium– or nitrate–nitrogen, the mixed nitrogen source was better for promoting the root activity of <i>C. oleifera</i> seedlings, and the best nitrate/ammonium ratio was 5:5.
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