Absorption of Water and 32P through Suberized and Unsuberized Roots of Loblolly Pine

Abstract

Measurements were made of the rate of intake of water and 32P through suberized and unsuberized roots and root segments from seedlings of Pinustaeda L. under a pressure gradient of 31 cm Hg (41 kPa), produced by use of a vacuum pump. Water and 32P intake through suberized root segments from seedlings in storage was only 11% of the intake through unsuberized segments from roots grown in nutrient solution. Water intake through entirely suberized root systems grown in nutrient solution was about 71% and 32P uptake about 58% of those through root systems grown in nutrient solution but with 40–50% of their surface unsuberized. Uptake of water and 32P through root segments and root systems grown in vermiculite was intermediate between that for seedlings grown in nutrient solution and that for dormant root systems. Removal of all unsuberized root surface reduced the total root surface by 42%, water uptake by 54%, and 32P uptake by 70% per seedling. These results indicate that absorption of water and mineral nutrients through suberized roots may play an important role in the water economy and mineral nutrition of woody plants.