Potassium influx into maize root systems

Journal Article · Sat Aug 01 00:00:00 EDT 1987 · Plant Physiology; (USA)

DOI:https://doi.org/10.1104/pp.84.4.1416· OSTI ID:6945728

Vale, F R; Jackson, W A; Volk, R J ^[1]

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1. North Carolina State Univ., Raleigh (USA)

Potassium influx into roots of dark-grown decapitated maize seedling (Zea mays L., cv Pioneer 3369A) was examined in presence and absence of ambient ammonium and at various root potassium concentrations. Six-day old seedlings which were dependent on the endosperm reserves for their energy source were exposed to KCl (labeled with {sup 86}Rb) ranging from 5 to 200 micromolar. At both low (13 micromoles per gram fresh weight) and high (100 micromoles per gram fresh weight) root potassium concentration, isotherms indicated two potassium influx systems, one approaching saturation at 50 to 100 micromolar potassium and an additional one tentatively considered to be linear. A mixed-type inhibition by ammonium for the low-concentration saturable system was indicated by a concomitant decrease in V{sub max} and increase in K{sub m}. High root potassium concentration decreased V {sub max} but had little effect on K{sub m} of this system. The rate constant for the second quasilinear system was decreased by ambient ammonium and by high root potassium status. Transfer of high potassium roots to potassium-free solutions resulted in an increase in influx within 2 hours; by 24 hours influx significantly exceeded that of roots not previously exposed to potassium. In roots of both low and high root potassium concentrations, potassium influx was restricted progressively as ambient ammonium increased to about 100 micromolar, but there was little further inhibition as ammonium concentrations increased beyond that to 500 micromolar. The data imply that potassium influx has two components, one subject to inhibition by ambient ammonium and one relatively resistant.

• OSTI ID: 6945728
• Journal Information: Plant Physiology; (USA), Vol. 84:4; ISSN 0032-0889
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
POTASSIUM
UPTAKE
ROOTS
PHYSIOLOGY
AMMONIUM COMPOUNDS
BIOLOGICAL EFFECTS
MAIZE
RUBIDIUM 86
SEEDLINGS
TRACER TECHNIQUES
ALKALI METAL ISOTOPES
ALKALI METALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CEREALS
DAYS LIVING RADIOISOTOPES
ELEMENTS
GRASS
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LILIOPSIDA
MAGNOLIOPHYTA
METALS
MINUTES LIVING RADIOISOTOPES
NUCLEI
ODD-ODD NUCLEI
PLANTS
RADIOISOTOPES
RUBIDIUM ISOTOPES
551001* - Physiological Systems- Tracer Techniques