Enhanced tolerance of high-p plants to environmental stresses is related to primary root diameter and potential root hydraulic conductivity for water and nutrient uptake.

Abstract

Glasshouse and field experiments were conducted over a period of 8 years (1994-2002) in Australia to understand the mechanism of tolerance to environmental stresses, particularly in response to increased soil phosphorus concentration. Studies included factorial experiments on white clover, cotton, and wheat subjected to frequent defoliation, water deficit and/or waterlogging stresses in different agroclimatic conditions. Morphological, physiological and anatomical measurements indicated importance of root growth and root activity, particularly the potential root hydraulic conductance of basal primary roots and associated uptake of water and nutrient under environmental stresses.

An increased supply of soil phosphorus above adequate amounts appears to increase the potential root hydraulic conductance per unit leaf area as a result of substantial increases in the number and size of xylem vessels. Under adverse environmental conditions, high-P supply also appears to increase the leaf expansionrate, size of the cell, and the size and number of vacuoles in each cell to store more solutes and water.