Osmotic properties of pea internodes in relation to growth and auxin action
The water transport properties of etiolated pea (Pisum sativum L.) internodes were studied using both dynamic and steady-state methods to determine (a) whether water transport through the growing tissue limits the rate of cell enlargement, and (b) whether auxin stimulates growth in part by increasing the hydraulic conductance of the growing tissue. Measurements using the pressure probe technique showed that the hydraulic conductivity of cortical cell membranes was the same for both slowly growing and auxin-induced rapidly growing cells (membrane hydraulic conductivity, about 1.5 x 10/sup -5/ centimeters per second per bar). In a second technique which measured the rate of water movement through the entire pea internode, the half-time for radial water flow was about 60 seconds and was not altered by auxin application. These results indicate that auxin does not alter the hydraulic conductance of pea stem tissue, either at the cellular or the whole tissue level. When the growth rate was altered by various treatments, including decapitation, auxin application, cold temperature, and KCN treatment, the water potential was independent of the growth rate of the stem. We attribute the depression of the water potential in young pea stems to the presence of solutes in the cell wall free space of the tissue. From the results of these dynamic and steady-state experiments, we conclude that the internal gradient in water potential (from the xylem to the epidermis) needed to sustain cell enlargement is small (no greater than 0.5 bar). Thus, the hydraulic conductance of the tissue is sufficiently large that it does not control or limit the rate of cell enlargement. 30 references, 5 figures, 4 tables.
- Research Organization:
- Univ. of Washington, Seattle
- DOE Contract Number:
- AT06-70ER73019
- OSTI ID:
- 5960477
- Journal Information:
- Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 72; ISSN PLPHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
AUXINS
BIOLOGICAL FUNCTIONS
COMPARATIVE EVALUATIONS
DATA
EXPERIMENTAL DATA
FUNCTIONS
GROWTH
HYDRAULIC CONDUCTIVITY
HYDROGEN COMPOUNDS
INFORMATION
LEGUMINOSAE
METABOLISM
NUMERICAL DATA
OXYGEN COMPOUNDS
PISUM
PLANT CELLS
PLANT GROWTH
PLANT GROWTH REGULATORS
PLANTS
SEEDLINGS
TRANSLOCATION
WATER