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

Abstract

In the present study, the root vigor and kinetic ch aracteristics of nitrogen absorption in potato cultivars was investigated through sand cult ivation and pot tests with nutrient solution. Four cultivars of potatoes, namely, Feiwu ruita, Yunshu301, Liangshu97, and Chuanyu56 were grown in nutrient solution matrix cu ltures. The result showed that: (1) Nitrogen uptake rates differed significantly among cultivars with different nitrogen efficiencies; (2) cultivars with High nitrogen-util ization-rate showed significantly higher root vigor, the average root vigor values of cultiv ars with the high nitrogen-utilization were 115% at seeding stage, 53% at tuber-bulking st age, and 18% at mature stage, respectively, higher than those of cultivars with t he low nitrogen-utilization; and (3) Root vigor varied according to growth stage and nitrogen supply i.e. cultivars with high nitrogen-utilization-rate showed enhanced root vigo r at the seedling stage under low- nitrogen conditions, while cultivars with low nitro gen-utilization rate showed reduced root vigor at the tuber-bulking and mature stages u nder high-nitrogen conditions. The kinetic characteristics of nitrogen uptake differed significantly among cultivars: (1) In comparison with cultivars with the low, high nitrog en-utilization showed lower K m and higher V max values; (2) The K m value for nitrate nitrogen uptake was higher than that for ammonium nitrogen uptake, especially in cultivars w ith low nitrogen-utilization ， ，， ， than those of ammonium nitrogen; (3) In cultivars with l ow nitrogen-utilization, the V max value for nitrate nitrogen was lower than that for ammoni um nitrogen; and (4) In cultivars with high nitrogen-utilization, the V max value for nitrate nitrogen was the opposite. The s tudy provides a basis for breeding high nitrogen-utiliza tion cultivars, thereby improving the efficiency of nitrogen fertilization. Keywords: High nitrogen utilization, Kinetics of absorption, Nitrogen form.