Maximum axial root growth pressure in pea seedlings: effects of measurement techniques and cultivars

Values of the maximum axial growth pressure (σ max ) of seedling pea (Pisum sativum L.) roots reported in the literature, obtained using different apparatuses and cultivars, range from 0.3 MPa to 1.3 MPa. To investigate possible reasons for this large range, we studied the effect of apparatus and cultivar on measurements of σ ma x in peas. We describe four types of apparatus which can be used to measure axial root growth force and hence σ max, and used them to measure σ max in seedling pea roots using cultivar Meteor. Two of these apparatuses were also used to compare σ max for three pea cultivars (Helka, Meteor and Greenfeast). Both cultivar and apparatus significantly affected σ max , but there were greater differences between apparatuses than between the three cultivars. Estimating root cross-sectional area from the diameter of cross-sections, rather than from in situ measurements (i.e. measurements made with the root still in place in the apparatus) may explain these differences.