Effects of some amino acid analogs on the uptake and transport of potassium and calcium in wheat triticum aestivum cultivar capelle and mung bean vigna radiata seedlings 1. cortical cell fluxes and transport to the stele in excised root segments as affected by p fluorophenylalanine

Thornton, B.; Macklon, A.E.S.

Journal of Experimental Botany 36(167): 919-929


ISSN/ISBN: 0022-0957
Accession: 005326243

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Effluxes of K+ and Ca2+ from root segments of both wheat, and mung bean were measured in the presence or absence of 2.0 mol m-3 p-fluorophenylalanine (p-FPA). The results were used to estimate the compartment contents and transmembrane K+ and Ca2+ fluxes in root cortex cells. Using the Ussing-Teorell flux equation as the criterion, it was concluded that entry of K+ from the outside solution to the cytoplasm, and from the cytoplasm to the vacuole were active in both wheat and mung bean. Also, in both species, Ca2+ entered the cytoplasm passively across the plasmalemma and was actively pumped back to the external solution. However, interpretation of the direction of active transport across the tonoplast depends upon an assumption about Ca2+ activity in the cytoplasm. The only qualitative effect of p-FPA was to alter the driving force for K+ influx, across the plasmalemma in wheat, from an active to a passive one. Quantitative effects of the analog were seen for K+ fluxes in both wheat and mung bean and for Ca2+ fluxes in wheat. The p-FPA reduced transport of K+ in both species, while transport of Ca2+ was unaffected. The implications of these results for the two pump hypothesis are discussed.