Effects of plant growth regulators on vegetative and reproductive growth of Dalbergia odorifera

Objective  To investigate the effects of plant growth regulators on vegetative and reproductive growth of Dalbergia odorifera, and provide useful suggestions for plantation management of D. odorifera with different purposes.

Method  We set up a randomized block experiment using 10-year-old D. odorifera. Leaves were sprayed with three different concentrations of gibberellin (GA₃), paclobutrazol (PP₃₃₃) or benzyladenine (6-BA). Changes in morphology, growth and dry weight of 1-year-old branch, flower and leaf at full-bloom stage were measured. The changing patterns of vegetative and reproductive growth after treating with plant growth regulators were investigated using statistical analysis software.

Result  Both type and concentration of plant growth regulators caused significant differences in vegetative and reproductive growth of D. odorifera (P<0.05). Foliar application of 200, 100 mg·L^–1 GA₃ or 500 mg·L^–1 6-BA significantly promoted vegetative growth of D. odorifera, while inhibited reproductive growth. Application of 200 mg·L^–1 GA₃ had the best inhibition effect on reproductive growth with the ratio of vegetative branch increased by 140.84% and inflorescence number reduced by 79.41% compared to control (P<0.05). Application of 100 mg·L^–1 GA₃ had the best promoting effect on vegetative growth with the vegetative branch length and diameter, compound leaf number and dry weight of simple leaf increased by 218.08%, 120.70%, 132.38% and 217.33% compared to control (P<0.05). On the other hand, foliar application of 1 500, 2 000 mg·L^–1 PP₃₃₃ and 50 mg·L^–1 6-BA significantly promoted the reproductive growth of D. odorifera. Application of 2 000 mg·L^–1 PP₃₃₃ had the best promoting effect on reproductive growth with the ratio of reproductive branch, the number and diameter of inflorescence increased by 73.50%, 50.37% and 31.30% respectively compared to control (P<0.05).

Conclusion  For plantation management of D. odorifera, foliar application of 200 mg·L^–1 or 100 mg·L^–1 GA₃ can inhibit reproductive growth and promote vegetative growth, and should be used for large timber production. Foliar application of 2 000 mg·L^–1 PP₃₃₃ can promote reproductive growth, and should be suitable for selective breeding.