*3.5. Changes in Endogenous Hormone Content and Ratio during the Rooting Process of Fruit Mulberry Cuttings*

3.5.1. Changes in Endogenous IAA

As exhibited in Figure 4A, the changes in IAA content in the treatment groups and the control group showed a trend of decreasing before increasing. In the initiation period, the IAA contents in the treatment groups were higher than that in the control group, suggesting that ABT-1 could promote the synthesis of endogenous IAA. During callus formation, the IAA content presented a decreasing trend, possibly due to the active respiration and metabolism of internal cells of cuttings that needed a large amount of IAA to form callus tissue. After root primordia broke through the callus tissue and produced numerous new roots, IAA synthesis was promoted, and the IAA content increased. The IAA content of ABT-1—500 mg·L−<sup>1</sup> (32.8 ng·g−1) was greater than that of ABT-1—200 mg·L−<sup>1</sup> (15.9 ng·g<sup>−</sup>1) and ABT-1—1000 mg·L−<sup>1</sup> (21.8 ng·g<sup>−</sup>1), and the control group (20.2 ng·g<sup>−</sup>1).

**Figure 4.** Effects of ABT-1 treatment on endogenous hormone level during the rooting process of fruit mulberry cuttings. Panels (**A**–**I**) exhibit changes of the levels of IAA, ABA, ZR, GA3, JA, SL, IBA, IAA/ABA, and IAA/ZR in the ABT-1 treatment groups and control group during the rooting stages. Different lowercase letters indicate remarkable differences among the treatments (LSD multiple comparison analysis, *<sup>p</sup>* < 0.05). B1—represents 200 mg·L−<sup>1</sup> ABT-1 treatment group, B2—denotes 500 mg·L−<sup>1</sup> ABT-1 treatment group, B3—signifies 1000 mg·L−<sup>1</sup> ABT-1 treatment group and CK2—refers to the control group. Stage 1—represents the initiation stage, Stage 2—denotes the callus formation stage and Stage 3—indicates the adventitious root formation and elongation stage.
