The effects of exogenous hormones on rooting process and the activities of key enzymes of Malus hupehensis stem cuttings

• Published in: PloS one 2017-02, Vol.12 (2), p.e0172320-e0172320
• Main Authors: Zhang, Wangxiang, Fan, Junjun, Tan, Qianqian, Zhao, Mingming, Zhou, Ting, Cao, Fuliang
• Format: Article
• Language: English
• Subjects: Acetic acid; Agrochemicals - metabolism; Antioxidants; Antioxidants (Nutrients); Apples; Biology and Life Sciences; Cell division; Critical point; Ecology and Environmental Sciences; Economic growth; Emergence; Engineering and Technology; Environmental management; Enzymatic activity; Enzyme activity; Enzymes; Genetic aspects; Hormones; Indoleacetic acid; Indoleacetic Acids - metabolism; Lignin; Malus; Malus - drug effects; Malus - enzymology; Malus - growth & development; Malus hupehensis; Medicine and Health Sciences; Naphthalene; Naphthaleneacetic Acids - metabolism; Physiology; Plant Growth Regulators - metabolism; Plant hormones; Plant Roots - drug effects; Plant Roots - enzymology; Plant Roots - growth & development; Plant Stems - drug effects; Plant Stems - enzymology; Plant Stems - growth & development; Polyamines; Rhizome - drug effects; Rhizome - enzymology; Rhizome - growth & development; Rooting; Sustainable development
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0172320

Malus hupehensis is an excellent Malus rootstock species, known for its strong adverse-resistance and apomixes. In the present study, stem cuttings of M. hupehensis were treated with three types of exogenous hormones, including indole acetic acid (IAA), naphthalene acetic acid (NAA), or green growth regulator (GGR). The effects and mechanisms of exogenous hormone treatment and antioxidant enzyme activity on adventitious root formation were investigated. The results showed that the apparent morphology of the adventitious root had four stages, including root pre-emergence stage (S0), early stage of root formation (S1), massive root formation stage (S2), and later stage of root formation (S3). The suitable concentrations of the three exogenous hormones, IAA, NAA and GGR, were 100 mg·L-1, 300 mg·L-1, and 300 mg·L-1, respectively. They shortened the rooting time by 25-47.4% and increased the rooting percentages of cuttings by 0.9-1.3 times, compared with that in the control. The dispersion in S0 stage was 3.6 times of that in the S1 stage after exogenous hormone application. The earlier the third critical point (P3) appeared, the shorter the rooting time and the greater the rooting percentage of the cuttings. During rhizogenesis, the activities of three antioxidant enzymes (POD, SOD, and PPO) showed an A-shaped trend. However, peak values of enzyme activity appeared at different points, which were 9 d before the P3, P3, and the fourth critical point (P4), respectively. Exogenous hormone treatment reduced the time to reach the peak value by 18 days, although the peak values of the enzymatic activities did not significantly changed. Our results suggested that exogenous hormone treatment mainly acted during the root pre-emergence stage, accelerated the synthesis of antioxidant enzymes, reduced the rooting time, and consequently promoted root formation. The three kinds of antioxidant enzymes acted on different stages of rooting.