The efficiency of uptake of a nutrient by plants is a function of their physiological and morphological properties, which may vary between cultivars of the same species. A study was carried out to determine root morphology and kinetic parameters of potassium (K) uptake in rice genotypes. The experiment was conducted in a laboratory and the plants cultivated in pots under artificial light. Treatments were represented by 11 rice genotypes (Avaxi, BRS Atalanta, BRS Bojuru, BRS Fronteira, BRS Querência, CNA 10754, CAN 10756, CNA 10757, BRA 1455, BRA 1024 and BRA 1073). Rice plants were grown in nutrient solution renewed every week, until the seven-leaf stage (V7) was reached, when root morphological parameters (length, mean radius, root area, wet weight, and dry weight) were evaluated. Potassium uptake kinetic parameters (maximum influx - Imax, Michaelis-Menten constant - Km and minimum solution concentration for absorption - Cmin) were also estimated. The amount of K accumulated by rice genotypes was directly related to the root area and to shoot growth, which differed among genotypes. The uptake kinetic parameters (Imax, Km and Cmin) varied between rice genotypes. The genotypes differed in K absorption rate per root unit. Considering the influx of K and root dry weight, the genotypes were classified into three groups of capacity of K acquisition: high potential (BRS Atalanta, Avaxi, BRS Querencia, BRA 1455 and BRA 1073); intermediate potential (BRS Fronteira, BRA 1024 and CNA 10754) and low potential (CNA 10756, BRS Bojuru and CNA 10757).
root length; root area; potassium influx; Oryza sativa L
