硝态氮供应对小麦根系形态发育和氮吸收动力学的影响

为给小麦氮素利用效率的提高及氮高效品种的选育提供依据，以秦麦11号和宁麦9号作为供试材料，采用溶液培养方法，研究了不同浓度硝酸盐对小麦根系形态发育特征和硝酸盐吸收动力学的影响。结果表明，在较低的浓度范围内，NO3-可增加小麦总根长和根尖数，促进根系生长；当NO3-浓度超过2 mmol/L时，总根长和根尖数受到强烈抑制，但由于根系平均直径的增加，根系总体积并未明显减少。两个供试小麦品种之间根系NO3-含量并无明显差异，而两个品种的叶片NO3-含量在介质NO3-浓度超过10 mmol/L时表现出了明显差异。叶片、根系NO3-含量与根冠比之间的关系可用一次函数来进行描述，与根长、根尖数之间的关系可用二次函数来进行描述。与宁麦9号相比，秦麦11号的NO3-吸收具有更高Vmax值和Km值，这可能与两个供试小麦品种根系形态特征的差异有关。

Effects of Nitrate Supply on Morphology Development and Nitrate Uptake Kinetics of Wheat Roots

Nitrate status in plants, which is closely related with the environmental nitrate supply, affects the root characteristics. The mechanism involved is still not clearly understood. In this study, Qinmai 11 and Ningmai 9 were selected as the experimental materials and solution culture method was used to explore the effects of nitrate supply on root morphology and nitrate uptake characteristics. Total root length and root tips of wheat seedlings were stimulated at low concentration of nitrate in the nutrient solution, while both were inhibited significantly when nitrate increased up to 2 mmol/L. For the increase of root average diameter at high nitrate supply level, total root volume did not showed a significant decrease tendency. Nitrate content in shoots and roots increased with the increase of nitrate supply. Nitrate content in roots presented no significant differences between two wheat varieties, while that in leaves were significantly different when medium nitrate was 10 mmol/L. Nitrate content in shoots and roots had a linear mathematic functions with root / shoot ratio, and had a parabola correlation with both total root length and root tips. Qinmai 11 showed higher Vmax and Km of nitrate uptake than Ningmai 9, which possibly had relations with the differences of root morphology between two wheat varieties.