Efficiency of Potassium Utilization by Barley Varieties: The Role of Subcellular Compartmentation

Memon, A. R., Saccomani, M. and Glass, A. D. M. 1985. Efficiencyof potassium utilization by barley varieties: The role of subcellularcompartmentation.?J. exp. Bot. 36: 1860–1876. The subcellulardistributions of K⁺ in roots of three barley (Hordeum vulgareL.) varieties, grown at 10 and 100 mmol m^–3 external K⁺(K⁺]_o) were estimated by compartmental analyses. In general,increased K⁺]_o caused a 2–3 fold increase in vacuolarK⁺], but cytoplasmic K⁺] increased only slightly. Nevertheless,the three varieties, which had been selected for study on thebasis of their different rates of K⁺ utilization, showed distinctdifferences in the allocation of K⁺ between cytoplasm and vacuole.At 10 mmol m^–3 K⁺]_o var. Betzes exhibited typical K⁺deficiency symptoms while var. Fergus and var. Compana did not,even though Betzes had higher K⁺] in shoots and roots. Theinefficient utilization of K⁺ in this variety appears to beassociated with a failure to mobilize vacuolar K⁺ into the cytoplasmiccompartment (the ratio of vacuolar: cytoplasmic K⁺ contentsfor Betzes was 4.1 compared to 2.7 and 2.5, respectively, forFergus and Compana). Fergus and Betzes, which demonstrate pronouncedgrowth responses to increased K⁺]₀ between 10 and 100 mmolm^–3, showed significant increases of cytoplasmic K⁺]in this range of K⁺]_o. By contrast, cytoplasmic K⁺] in Compana,a variety whose growth is not stimulated by increased K⁺]₀(from 10 to 100 mmol m^–3) showed virtually no increase.It is suggested that the efficiency of K⁺ utilization and thegrowth response to K⁺]₀ in these varieties are functions ofthe subcellular distribution of this ion between cytoplasm andvacuole. Key words: Barley varieties, K⁺ subcellular compartmentation, utilization efficiency