Cell wall yield properties of growing tissue: evaluation by in vivo stress relaxation. [Pisum sativus L]

Journal Article · Sat Jun 01 00:00:00 EDT 1985 · Plant Physiol.; (United States)

OSTI ID:5620371

Cosgrove, D J

Growing pea stem tissue, when isolated from an external supply of water, undergoes stress relaxation because of continued loosening of the cell wall. A theoretical analysis is presented to show that such stress relaxation should result in an exponential decrease in turgor pressure down to the yield threshold (Y), with a rate constant given by phi epsilon where phi is the metabolically maintained irreversible extensibility of the cell wall and epsilon is the volumetric elastic modulus of the cell. Stress relaxation was measured in pea (Pisum sativus L.) stem segments using the pressure microprobe technique. From the rate of stress relaxation, phi of segments pretreated with water was calculated to be 0.08 per megapascal per hour while that of auxin-pretreated tissue was 0.24 per megapascal per hour. These values agreed closely with estimates of phi made by a steady-state technique. The yield threshold (0.29 megapascal) was not affected by auxin. A theoretical analysis is also presented to show that the tissue hydraulic conductance may be estimated from the T/sub 1/2/ of tissue swelling. Experimentally, pea stems had a swelling T/sub 1/2/ of 2.0 minutes, corresponding to a relative hydraulic conductance of about 2.0 per megapascal per hour. This value is at least 8 times larger than phi. From these data and from computer modeling, it appears that the radial gradient in water potential which sustains water uptake in growing pea segments is small (0.04 megapascal). This means that hydraulic conductance does not substantially restrict growth. The results also demonstrate that the stimulation of growth by auxin can be entirely accounted for by the change in phi.

• Research Organization: Pennsylvania State Univ., University Park
• OSTI ID: 5620371
• Journal Information: Plant Physiol.; (United States), Vol. 78:2
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CELL WALL
HYDRAULIC CONDUCTIVITY
PLANT GROWTH
PHYSIOLOGY
PLANT STEMS
STRESS RELAXATION
AUXINS
BIOLOGICAL STRESS
COMPUTERIZED SIMULATION
ELASTICITY
EQUATIONS
IN VIVO
METABOLISM
PEAS
PRESSURE MEASUREMENT
SWELLING
UPTAKE
WATER
CELL CONSTITUENTS
FOOD
GROWTH
HYDROGEN COMPOUNDS
MECHANICAL PROPERTIES
OXYGEN COMPOUNDS
PLANT GROWTH REGULATORS
PLANTS
RELAXATION
SIMULATION
TENSILE PROPERTIES
VEGETABLES
550500* - Metabolism