Nature and origin of the calcium asymmetry-arising during gravitropic response in etiolated pea epicotyls
Seven day old etiolated pea epicotyls were loaded symmetrically with /sup 3/H-indole 3-acetic acid (IAA) or /sup 45/Ca/sup 2 +/, then subjected to 1.5 hours of 1g gravistimulation. Epidermal peels taken from top and bottom surfaces after 90 minutes showed an increase in IAA on the lower side and of Ca/sup 2 +/ on the upper side. Inhibitors of IAA movement (TIBA, 9-hydroxyfluorene carboxylic acid) block the development of both IAA and Ca/sup 2 +/ asymmetries, but substances known to interfere with normal Ca/sup 2 +/ transport do not significantly alter either IAA or Ca/sup 2 +/ asymmetries. These substances, however, are active in modifying both Ca/sup 2 +/ uptake and efflux through oat and pea leaf protoplast membranes. The authors conclude that the /sup 45/Ca/sup 2 +/ fed to pea epicotyls occurs largely in the cell wall, and that auxin movement is primary and Ca/sup 2 +/ movement secondary in gravitropism. They hypothesize that apoplastic Ca/sup 2 +/ changes during the graviresponse because it is displaced by H/sup +/ secreted through auxin-induced proton release. This proposed mechanism is supported by localized pH experiments, in which filter paper soaked in various buffers was applied to one side of a carborundum-abraded epicotyls. Buffer at pH 3 increased calcium loss from the side to which it is applied, whereas pH 7 buffer decreases it. Moreover, 10 micromolar IAA and 1 micromolar fusicoccin, which promote H/sup +/ efflux, increase Ca/sup 2 +/ release from pea epicotyl segments, whereas cycloheximide, which inhibits H/sup +/ efflux, has the reverse effect.
- Research Organization:
- Yale Univ., New Haven, CT (United States)
- OSTI ID:
- 5515241
- Journal Information:
- Plant Physiol.; (United States), Vol. 85:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALCIUM COMPOUNDS
MEMBRANE TRANSPORT
PISUM
PLANT GROWTH
ACETIC ACID
CALCIUM 45
CATIONS
CELL WALL
EPIDERMIS
ION EXCHANGE
PHOTOSYNTHETIC MEMBRANES
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ANIMAL TISSUES
BACTERIA
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CALCIUM ISOTOPES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHARGED PARTICLES
DAYS LIVING RADIOISOTOPES
EPITHELIUM
EVEN-ODD NUCLEI
GROWTH
INTERMEDIATE MASS NUCLEI
IONS
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LEGUMINOSAE
MEMBRANES
MICROORGANISMS
MONOCARBOXYLIC ACIDS
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
PLANTS
RADIOISOTOPES
RHIZOBIUM
SKIN
TISSUES
550201* - Biochemistry- Tracer Techniques