Effect of mechanical impedance on root growth and morphology of two varieties of pea (Pisum sativum L.)

Abstract

SUMMARYTwo pea (Pisum sativum L.) varieties (Progreta and Solara) were grown under controlled conditions for 7 or 15 days in perspex cylinders filled with moist vermiculite and for 10 days in moist sandy clay loam topsoil packed to bulk densities of 1.0, 12, 1.4 or 17 Mg m−3(with initial penetration resistances (PR) of; 0.037, 0.101, 0.246, 0.506 and 2–366 MPa respectively). The increase in PR from 0.101 to 0.506 MPa significantly decreased axis growth rate of Progreta but not of Solara. However, at a PR of 2366 MPa, axis growth rate of Solara was reduced to significantly less than that of Progreta. Thus experiments to describe intervarietal differences in root response to mechanical impedance need to be performed at a range of different mechanical impedances.Few, if any, laterals emerged from axes growing across large gaps between aggregates suggesting that regular stimulation of the root tip is required to trigger lateral emergence. Significant correlations (P= 0.001) between first order lateral diameter and elongation rate were observed for roots of both varieties grown in moist vermiculite but not in soil. This relationship may indicate a general feature that thinner roots of any order are slower growing in a gap‐free and uniformly aggregated medium.