Uptake of potassium by Setaria anceps and Macroptilium atropurpureum from the same standard solution culture

Abstract

The influence of potassium supply on growth and potassium uptake by Setavia anceps cv. Nandi and Macroptilium atropurpureum cv. Siratro grown in association in standard solution culture was studied. Different degrees of competition were induced by introducing Siratro plants of three different ages (6, 12, 18 days) to the experimental solutions at the commencement of the experiment. Setaria seedlings were 12 days old at this point. Competition between the two species was compared at a high and at a low level of potassium supply. Throughout the duration of the experiment, Setaria plants absorbed potassium at a much greater rate than did the Siratro plants grown in association. Although the potassium absorption rates of Setaria declined more rapidly as the solution supply was exhausted, they generally remained above those for Siratro. The higher potassium concentrations obtained in Setaria than in Siratro plants grown in association ensure a superior ability for the grass to continue growth following exhaustion of the potassium supply. Rapid early growth of Siratro plants in some situations may provide some advantage in competing for the available potassium supply simply through a greater root mass.