PHYSIOLOGICAL INVESTIGATIONS ON ALARIA ESCULENTA (LAMINARIALES,PHAEOPHYCEAE). III. EXUDATION BY THE BLADE1,2,3

Comparison of exudation rate of medullary conducting cells in the midrib of Alaria esculenta (L.) Grev. showed lowest rates for the blade meristem and highest rates in the non-growing region, 300–500 mm from the meristem. Holding plants under continuous darkness or severing the wings from the midrib reduced exudation rate by 26 and 37%, respectively. Osmotic pressure of exudate in sink (meristem) and source (non-growing region, up to 500 mm from the meristem) were similar (34.6–36.1 · 10²kpa). Pressure flow mechanism of translocation is evaluated in Alaria.