The Influence of Ammonium and Chloride on Potassium and Nitrate Absorption by Barley Roots Depends on Time of Exposure and Cultivar

摘要

Net uptakes of K⁺ and NO3⁻ were monitored simultaneously and continuously for two barley (Hordeum vulgare) cultivars, Prato and Olli. The cultivars had similar rates of net K⁺ and NO3⁻ uptake in the absence of NH4⁺ or Cl⁻. Long-term exposure (over 6 hours) to media which contained equimolar mixtures of NH4⁺, K⁺, Cl⁻, or NO3⁻ affected the cultivars very differently: (a) the presence of NH4⁺ as NH4Cl stimulated net NO3⁻ uptake in Prato barley but inhibited net NO3⁻ uptake in Olli barley; (b) Cl⁻ inhibited net NO3⁻ uptake in Prato but had little effect in Olli; and (c) NH4⁺ as (NH4)2SO4 inhibited net K⁺ uptake in Prato but had little effect in Olli. Moreover, the immediate response to the addition of an ion often varied significantly from the long-term response; for example, the addition of Cl⁻ initially inhibited net K⁺ uptake in Olli barley but, after a 4 hour exposure, it was stimulatory. For both cultivars, net NH4⁺ and Cl⁻ uptake did not change significantly with time after these ions were added to the nutrient medium. These data indicate that, even within one species, there is a high degree of genotypic variation in the control of nutrient absorption.