Kinetics of nitrate absorption and root cation exchange capacity of some polyembryonic mango (Mangifera indica) rootstocks.
Murthy S. V. K., Kotur S. C.
Author Affiliation: Division of Soil Science and Agricultural Chemistry, Indian Institute of Horticultural Research, Hessaraghatta Lake P.O., Bangalore 560089, India.
Plant Physiology & Biochemistry (New Delhi) 25 : 25-27
Abstract : Kinetics of N (NO3-) uptake by polyembryonic seedlings of mango rootstocks (10 cultivars) was studied during 1993-94 using 300-day-old seedlings grown in sand and supplied with a complete nutrient solution of known NO3- concentration. Among the rootstocks screened, Bangalora had the highest Imax (maximum rate of absorption) followed by Vellaikolamban, while Nekkarai and Peach had very low Imax. Nekkarai had low and Bangalora very high Km values (concentration of NO3- in the equilibrium solution at which the average rate of NO3- uptake was 50% of Imax). The inflow rate of NO3- (In) was high in Bangalora and Vellaikolamban. High NO3- inflow rate in these rootstocks was mainly due to the higher number of absorption sites as denoted by high Imax of their roots. Despite high affinity for NO3- (low Km and low Cmin (minimum NO3- concentration at which no net absorption takes place)) in Nekkarai, the rate of inflow was of lower order due to low Imax. Bangalora was responsive to higher concentrations of N due to its higher Imax. Vellaikolamban and Prior may do well even in marginal soils due to their low Cmin. Nekkarai, Olour and Kensington had high root cation exchange capacities, indicating their capacity to absorb divalent cations like Ca and Mg more efficiently than other rootstocks.