Morphological changes in roots of Bothriochloa ischaemum intercropped with Lespedeza davurica following phosphorus application and water stress

Abstract

Root morphological characteristics are important parameters for the evaluation of plant adaptation to stress environment. In this study, a pot experiment was conducted to investigate changes in the root morphology of Bothriochloa ischaemum intercropped with Lespedeza davurica under three soil water regimes and two phosphorus (P) fertilizer treatments. Results showed that root biomass (RB) per B. ischaemum plant decreased as its proportion increased in the mixtures. There were no significant differences in root:shoot ratio (RSR) among the mixture ratios, and P application did have consistent effects on the RSR. Bothriochloa ischaemum tended to have smaller root surface area (RSA), root average diameter (RAD), specific root length (SRL), and specific root area (SRA) under water stress conditions. There was a negative linear relationship between RB and RSA under each water and P treatment. Negative and positive linear relationships were found between RB and TRL (total root length), TRL and RSA, respectively, except under severe water stress without P application. P application decreased the RAD and increased the SRA and SRL of B. ischaemum under water stress. All these suggest two apparent response mechanisms for B. ischaemum under water stress and P application: an increase in length of small diameter roots and decrease in root weight density.