Membrane vesicles: A simplified system for studying auxin transport
Indoleacetic acid (IAA), the auxin responsible for regulation of growth, is transported polarly in plants. Several different models have been suggested to account for IAA transport by cells and its accumulation by membrane vesicles. One model sees diffusion of IAA driven by a pH gradient. The anion of a lipophilic weak acid like IAA or butyrate accumulates in an alkaline compartment in accord with the size of the pH gradient The accumulation of IAA may be diminished by the permeability of its lipophilic anion. This anion leak may be blocked by NPA. With anion efflux blocked, a gradient of two pH units would support an IAA accumulation of less than 50-fold at equilibrium (2) Another model sees diffusion of IAA in parallel with a saturable symport (IAA[sup [minus]] + nH[sup +]), driven by both the pH gradient and membrane voltage. Such a symport should be highly accumulative, however, with a lipophilic weak acid such as IAA, net diffusive efflux of IAAH whenever IAAHI[sub i] > IAAH[sub o] would constitute a leak. (3) A third model sees a pH change driven IAA uptake and saturable symport enhanced by internal binding sites. Following pH gradient-driven accumulation of IAA, the anion may bind to an intravesicular site, permitting further uptake of IAA. NPA, by blocking anion efflux, enhances this binding. We have reported that membrane vesicles isolated from actively growing plant tissues are a good system for studying the mechanisms involved in the transport and accumulation of auxin.
- Research Organization:
- Yale Univ., New Haven, CT (United States)
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-85ER13337
- OSTI ID:
- 6874189
- Report Number(s):
- DOE/ER/13337-4; ON: DE93007961
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
090700* -- Biomass Fuels-- Resources-- (1990-)
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553002 -- Agriculture & Food Technology-- Horticulture-- (1987-)
59 BASIC BIOLOGICAL SCIENCES
60 APPLIED LIFE SCIENCES
AUXINS
DOCUMENT TYPES
GROWTH
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
PLANT GROWTH
PLANT GROWTH REGULATORS
PROGRESS REPORT
TRACER TECHNIQUES
TRANSLOCATION
TRITIUM COMPOUNDS