Root Vigor and Kinetic Characteristics and Nitrogen Use Efficiencies of Different Potato (Solanum tuberosum L.) Cultivars

In the present study, the root vigor and kinetic characteristics of nitrogen absorption in potato cultivars was investigated through sand cultivation and pot tests with nutrient solution. Four cultivars of potatoes, namely, Feiwuruita, Yunshu301, Liangshu97, and Chuanyu56 were grown in nutrient solution matrix cultures. The result showed that: (1) Nitrogen uptake rates differed significantly among cultivars with different nitrogen efficiencies (2) cultivars with High nitrogenutilizationrate showed significantly higher root vigor, the average root vigor values of cultivars with the high nitrogenutilization were 115% at seeding stage, 53% at tuberbulking stage, and 18% at mature stage, respectively, higher than those of cultivars with the low nitrogenutilization and (3) Root vigor varied according to growth stage and nitrogen supply i.e. cultivars with high nitrogenutilizationrate showed enhanced root vigor at the seedling stage under lownitrogen conditions, while cultivars with low nitrogenutilization rate showed reduced root vigor at the tuberbulking and mature stages under highnitrogen conditions. The kinetic characteristics of nitrogen uptake differed significantly among cultivars: (1) In comparison with cultivars with the low, high nitrogenutilization showed lower Km and higher Vmax values (2) The Km value for nitrate nitrogen uptake was higher than that for ammonium nitrogen uptake, especially in cultivars with low nitrogenutilization，than those of ammonium nitrogen (3) In cultivars with low nitrogenutilization, the Vmax value for nitrate nitrogen was lower than that for ammonium nitrogen and (4) In cultivars with high nitrogenutilization, the Vmax value for nitrate nitrogen was the opposite. The study provides a basis for breeding high nitrogenutilization cultivars, thereby improving the efficiency of nitrogen fertilization.