Studies of the Uptake of Nitrate in Barley : IV. Electrophysiology.

摘要: Transmembrane electrical potential differences (Δψ) of epidermal and cortical cells were measured in intact roots barley (Hordeum vulgare L. cv Klondike). The effects exogenous NO3− on Δψ (in the concentration range from 100 micromolar to 20 millimolar) investigated probe mechanisms nitrate uptake by high-affinity (HATS) low-affinity (LATS) transport systems for uptake. Both caused depolarization Δψ, demonstrating that LATS (like HATS) is probably mediated an electrogenic cation (H+?) cotransport system. Membrane HATS was “inducible” NO3−, saturable with respect [NO3−]. By contrast, constitutive, first-order response external H+ fluxes, 200 5 millimolar Ca(NO3)2 solutions, failed alkalinize media as anticipated a 2 H+:1 symport. However, switching K2SO4 solutions (which strongly acidifying) KNO3 at same K+ marked reductions efflux. These observations are consistent via symports. establish essentially similar those reported Lemna Zea mays earlier workers. There are, nevertheless, distinct between corn their quantitative responses NO3−.