Developmental changes in plant resistance to water flow in Pisum sativum (L.)

Soil and plant resistance to water flow under field conditions in pea (Pisum sativum L.) plants were measured at six ages. Transpiration flux, leaf and soil water potentials were used to calculate the total resistance to water flow using the Ohmʹs law analogy. Plant resistance was estimated from the slope of the water potential difference ( (delta)(psi)) vs. transpiration (Q) relationship. Plant growth, root density and soil water content distribution were measured. Leaf area and root length both increased until the end of seed filling and decreased during seed maturation. Total resistance decreased with the transpiration flux in a non-linear relationship. Plant resistance estimated as the slope of the ((delta)(psi))vs. Q regression line increased until pod filling and then decreased. The increased resistance to water flow during pod filling was associated with a 10% increase in cell wall thickness.