Phosphorus deficiency promotes the lateral root growth of Fraxinus mandshurica seedlings

Abstract

AbstractThis study aimed to evaluate the effects of phosphorus (P) deficiency on the lateral root growth of Fraxinus mandshurica seedlings and to reveal the potential molecular mechanisms involved. F. mandshurica seedlings were treated with various concentrations of P (0, 0.5, 1, and 2 mM KH2PO4) for 15 d. The growth of lateral roots was quantified by the number of lateral roots, total root length, total root surface area, and root : shoot ratio. Additionally, the levels of endogenous hormones and acid phosphatase were determined in the lateral roots of F. mandshurica seedlings using enzyme‐linked immunosorbent assay (ELISA). The transcription of 17 FmWRKYs and FmPHR1 was detected in the lateral roots of F. mandshurica seedlings using quantitative real‐time PCR (qRT‐PCR). F. mandshurica seedlings under P deficiency (0 mM) exhibited significantly higher number of lateral roots, total root length, total root surface area, and root : shoot ratio than those under P supply. P deficiency significantly decreased the levels of indole‐3‐acetic acid, brassinolide, and ethylene, and increased the levels of gibberellins 3, cytokinin, abscisic acid, and acid phosphatase in the lateral roots of F. mandshurica seedlings when compared to seedlings with P supply. In addition, the transcription of four FmWRKYs, including FmWRKY6, FmWRKY23, FmWRKY44, and FmWRKY71, as well as FmPHR1 were significantly higher in the lateral roots of F. mandshurica seedlings under P deficiency compared to seedlings treated with 1 mM P. Phosphorus deficiency promoted the lateral root growth of F. mandshurica seedlings and this process may be associated with the up‐regulation of FmWRKY6, FmWRKY23, FmWRKY44, FmWRKY71, and FmPHR1.