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<p>This study aimed to optimize an ex vitro rooting protocol for early-sprouting <i>Toona sinensis</i> and elucidate the underlying physiological and biochemical mechanisms during adventitious root (AR) formation. Using cultured seedlings as explants, a four-factor three-level orthogonal design was employed to evaluate the effects of hormone type, concentration, dipping duration and substrate composition on ex vitro rooting. The changes in nutrients, enzyme activities and endogenous hormones during the AR induction stages were analyzed: initial transplantation (day 1), root primordium induction (day 8), AR formation (day 11) and AR elongation (day 14). The optimal rooting protocol involved treating the stem bases with 10&#xa0;mg/L ABT-1 for 30&#xa0;s, followed by transplantation into a peat: vermiculite (1:1, v/v) substrate, which achieved a rooting rate of 100%, with 32.00 root tips per plant and an average root length of 2.67&#xa0;cm. Anatomical observations revealed that the rooting type is characterized by cortical rooting, with root primordia originating from the cortex or vascular cambium. Dynamic changes in physiological parameters revealed that stress-related hormones (ABA, JA and SA) were upregulated during root induction, which enhanced the activities of antioxidant enzymes (SOD, POD and PPO) and alleviated oxidative stress. Concurrently, GA3 biosynthesis was downregulated to facilitate root initiation. IAA and ZR synergistically promoted root primordium differentiation and development. The sustained elevation of IAA content further enhanced POD activity, stimulated lignin and protein biosynthesis, and accelerated metabolic activity as well as sugar consumption, thereby supporting AR elongation. This study established an efficient ex vitro rooting system for early-sprouting <i>T. sinensis</i> and clarified the physiological and biochemical mechanisms underlying the regulation of AR development. These findings provide both theoretical insights and practical guidance for improving propagation protocols for this species.</p>

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Ex vitro adventitious root induction and physio-biochemical changes during adventitious root formation in early-sprouted Toona sinensis

  • 期刊论文

  • 发表日期：

    2025年12月8日

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  • Meiru Xu,
  • Zhangxu Pan,
  • Guangxia Wang,
  • Peiyun He,
  • Gaoyin Wu

摘要

This study aimed to optimize an ex vitro rooting protocol for early-sprouting Toona sinensis and elucidate the underlying physiological and biochemical mechanisms during adventitious root (AR) formation. Using cultured seedlings as explants, a four-factor three-level orthogonal design was employed to evaluate the effects of hormone type, concentration, dipping duration and substrate composition on ex vitro rooting. The changes in nutrients, enzyme activities and endogenous hormones during the AR induction stages were analyzed: initial transplantation (day 1), root primordium induction (day 8), AR formation (day 11) and AR elongation (day 14). The optimal rooting protocol involved treating the stem bases with 10 mg/L ABT-1 for 30 s, followed by transplantation into a peat: vermiculite (1:1, v/v) substrate, which achieved a rooting rate of 100%, with 32.00 root tips per plant and an average root length of 2.67 cm. Anatomical observations revealed that the rooting type is characterized by cortical rooting, with root primordia originating from the cortex or vascular cambium. Dynamic changes in physiological parameters revealed that stress-related hormones (ABA, JA and SA) were upregulated during root induction, which enhanced the activities of antioxidant enzymes (SOD, POD and PPO) and alleviated oxidative stress. Concurrently, GA3 biosynthesis was downregulated to facilitate root initiation. IAA and ZR synergistically promoted root primordium differentiation and development. The sustained elevation of IAA content further enhanced POD activity, stimulated lignin and protein biosynthesis, and accelerated metabolic activity as well as sugar consumption, thereby supporting AR elongation. This study established an efficient ex vitro rooting system for early-sprouting T. sinensis and clarified the physiological and biochemical mechanisms underlying the regulation of AR development. These findings provide both theoretical insights and practical guidance for improving propagation protocols for this species.