WATER BALANCE IN THE ONION ROOT: RELATION OF VOLUME INTAKE TO VOLUME EXUDATE OF EXCISED ROOTS AND ISOLATED ROOT SEGMENTS

Abstract

Expts. were run under controlled conditions using calibrated photometers attached in a horizontal position to an upright glass rod. Vol. absorption and vol. exudation in a saturated atmosphere usually increased with time during a 24-hour period following excision; simultaneous fluctuations, sometimes opposite in direction, in both vol. absorption and vol. exudation occurred from one 2-hr, interval to another. The ratio, (vol. exudation)/vol. absorption, which was seldom unity during the first interval following excision, approached or reached unity with time. The direction of longitudinal transport of water through an isolated root segment evi-dently depends upon its age and upon its position on the longitudinal axis before cutting. The vector forces of trans-port are chiefly radial in isolated segments which are rela-tively older whereas in younger segments both longitudinal and radial factors are involved.