Effects of GA₄ on Growth, Quality and Endogenous Hormones of Dendrobium officinale

In order to explore the regulating effect of the new type of gibberellin GA₄ on the growth and development of Dendrobium offcinale, the treatment groups with different concentrations of GA₄ were set up, with GA₃ as the positive control and clean water as the blank control. The effects of GA₄ on the growth and quality of Dendrobium offcinale were determined, and the contents of the three endogenous hormones, such as the auxin (IAA), gibberic acid (GA₃) and zeatin (ZT) were determined by using the high performance liquid chromatography. The results showed that the plant height, plant diameter, biomass, polysaccharide content and total content of Dendrobium offcinale increased with the increase of GA₄ concentration. GA₄ 40 and GA₄ 80 had the most significant effects on the growth and quality of Dendrobium offcinale during the harvest period. Except for the plant height, the other indexes in the treatment groups of GA₄ 20 and GA₄ 40 were significantly higher than those in the positive control with the same concentration of GA₃ and blank control. The correlation analysis showed that the plant diameter and biomass were the key growth indicators affecting the quality of Dendrobium offcinale. The exogenous spraying of GA₄ could significantly affect the contents of IAA, GA₃ and ZT in Dendrobium offcinale. The contents of these three endogenous hormones increased significantly after 100 days of the treatment, and were significantly higher than those in the positive and blank controls. GA₄ may break the summer dormancy by regulating the endogenous hormones, causing the secondary growth of plants, thereby promoting the growth and quality of Dendrobium offcinale. The results could provide references for the development and utilization of GA₄.