Activity of root systems of six plant species at different stages of development

Summary A number of data on root performance of six different crop species during development were measured. The plants wre cultivated in nutrient solution. Normal plant requirements were in the range of 4 mg O₂ per g dry root per hour, 0.2–4μg K per cm² total root surface per hour,² 0.2–2μg NO₃ per om² total root surface per hour. An attempt was made to establish a ratio between forced water entry and total root surface as a measure of functional root surface. The indication is that the relative surface of permeable root remains dominant during the phase of exponential growth and declines thereafter. The data collected are considered to be representative of normal requirements. They compare well with results published in the literature.