Water Uptake by Mycorrhizal Roots of Radiata Pine Seedlings.

Abstract

Seedlings of radiata pine (Pinus radiata D. Don) grown in a sandy soil inoculated with Rhizopogon luteolus had 72% of their short roots mycorrhizal at age 5 months whereas the uninoculated controls had only 6.0 %.

When water was withheld from the soil and soil water matric potential became more negative, the leaf water potential of both inoculated and uninoculated plants became more negative, transpiration rate was reduced, and the derived resistance of the plant plus soil to the flow of water increased. There was no significant difference between inoculated and uninoculated plants in transpiration rate, but leaf water potential was more negative and consequently the derived resistance of plant plus soil was greater in the inoculated plants. The resistance of plant plus soil was partitioned using a simple whole-plant model. Resistance within the soil was considered more significant than that in the plant, and the greater soil resistance associated with the inoculated plants was considered to be due to differences in root geometry.