| Abstract: | A technique has been developed for the study of pathways ofwater movement in the xylem and free space of wheat leaves.Plants were treated with Lead-EDTA chelate through either theroots or the leaves; after treatment the lead was precipitatedin situ as lead sulphide with hydrogen sulphide gas and itslocation determined by light and electron microscopy. Bulk water movement was in the lumen of the xylem, where therewas always a heavy deposit of lead sulphide after root treatments.Outside the xylem the deposits were confined to the cell wallsand were most dense in the middle lamella. Deposits were notfound in the cells themselves. The main zones of water loss,marked by heavy deposits of lead sulphide, were associated withthe stomata, the junctions of the periclinal walls of the epidermalcells, and the cuticle, leaf hairs, and specialized epidermalcells with pitted walls associated with the vascular bundles. Entry of lead chelate into the leaves was adequately describedby a diffusion model. The free space seemed to be located mainlyin the water of hydration of the pectin middle lamella and wasesmated to occupy 3 to 5 per cent of the volume of the tissue. |
