Movement and Distribution of THO in Tissue Water and Vapor Transpired by Shoots of <i>Helianthus</i> and <i>Nicotiana</i>

Abstract

Various authors (1, 2, 3, 9) have reported that tritiated water as applied to plant roots does not fully exchange with water of various aerial organs, particularly leaves, even after long period of observation. This incomplete equality between tritium concentration in tissue water and external sources has been attributed to an inaccessible component of tissue water which does not exchange (2). In this report this hypothesis is tested experimentally. Data reported here were obtained by use of THO for appraising the pattern of movement and distribution of tritium in sunflower and tobacco. Influx and efflux of tritium were measured in stems and leaves of intact plants andl transpired vapor in both open and closed systems.