Exogenous hormone application regulates dwarf mutant plant height in Sophora davidii (Franch.) Skeels by changing endogenous hormone levels

Dwarf mutants are valuable materials for investigating plant gene function and developing new crop varieties. In the present study, dwarf mutant (D-CK) and wild-type (W-CK) Sophora davidii (Franch.) Skeels plants foliarly sprayed with distilled water were used as controls, and dwarf mutants were treated with different concentrations of gibberellin A3 (GA3; 20, 40 and 60 mg L-1), brassinosteroid (BR; 12.5, 25 and 50 mg L-1); and auxin indole-3-acetic acid (IAA; 12.5, 25 and 50 mg L-1) to study the changes in plant height at 20, 40 and 60 d after exogenous hormone spraying. The changes in endogenous contents of IAA, GA3, BR, abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) and IAA:ABA ratio in the dwarf mutant plants were also measured at 20, 40 and 60 d after exogenous hormone application. The dwarf mutants reverted to the W-CK height phenotype after 60 d of exogenous spraying with different concentrations of GA3 and BR (except 50 mg center dot L-1), but after exogenous spraying with IAA, dwarf mutants did not revert to the W-CK height phenotype. Compared with D-CK plants, endogenous GA3, BR and IAA contents in dwarf mutant plants increased to some extent with exogenous spraying of GA3, BR and IAA. The results indicated that exogenous spraying of different concentrations of GA3 and BR regulated S. davidii plant height by promoting the secretion of endogenous GA3, BR, IAA and SA and inhibiting endogenous ABA secretion in dwarf mutant. The height of mutants was sensitive to exogenous GA3 and BR but not to exogenous IAA.