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

Values of the maximum axial growth pressure (sigma(max)) of seedling pea (P isum sativum L.) roots reported in the literature, obtained using different apparatuses and cultivars, range from 0.3 MPa to 1.3 MPa. To investigate p ossible reasons for this large range, we studied the effect of apparatus an d cultivar on measurements of sigma(max) in peas. We describe four types of apparatus which can be used to measure axial root growth force and hence s igma(max), and used them to measure sigma(max) in seedling pea roots using cultivar Meteor. Two of these apparatuses were also used to compare sigma(m ax) for three pea cultivars (Helka, Meteor and Greenfeast). Both cultivar a nd apparatus significantly affected sigma(max), but there were greater diff erences between apparatuses than between the three cultivars. Estimating ro ot cross-sectional area from the diameter of cross-sections, rather than fr om in situ measurements (i.e. measurements made with the root still in plac e in the apparatus) may explain these differences.