Objective To study the effect of plant growth inhibitors on growth, leaf morphology and photosynthesis of Euonymus japonicus, and provide technical guidance for the chemical pruning shrubs.

Method One-year-old E. japonicus cutting stocks planted into hedge were treated with 3 kinds of growth inhibitors, Paclobutrazol (PP₃₃₃), triiodobenzoic acid (TIBA) and abscisic acid (ABA) by foliar spraying in the nursery of Beijing Forestry University. Then the growth, leaf morphology and photosynthesis were measured.

Result These 3 kinds of chemicals can inhibit both plant height growth and shoot growth, and PP₃₃₃ performed the best. The time of inhibitory effect of high concentration PP₃₃₃ lasted longer. The leaf area, leaf width and leaf thickness were higher than the control with PP₃₃₃ in the short term. PP₃₃₃ increased photosynthetic rate by increasing leaf thickness, stomatal conductance, mesophyll conductance and chlorophyll content and it reduced water use efficiency by increasing the transpiration rate. The leaf length and leaf thickness significantly reduced, but the leaf thickness increased with TIBA concentration increasing. Photosynthetic rate reduced in TIBA mainly due to reduced leaf area, mesophyll conductance, stomatal conductance, intercellular CO₂ concentration and chlorophyll content. The Leaf area (except 10 mg·L^-1 ABA) and leaf length increased, but the leaf thickness reduced with ABA. ABA can reduce photosynthetic rate mainly by reducing the mesophyll conductance, stomatal conductance and chlorophyll content. TIBA and ABA increased water use efficiency by reducing the transpiration rate.

Conclusion All the 3 kinds of chemicals can inhibit both plant height growth and shoot growth, and affect leaf development, and then affect leaf photosynthesis. PP₃₃₃ with a concentration of 800 mg·L^-1 performs the best.