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<p><i>Guadua amplexifolia</i> J. Presl, a neotropical bamboo species, is of emerging economic importance due to the physical and mechanical properties of its culms. Although protocols for in vitro culture have been developed for other bamboo species, previous attempts with <i>G. amplexifolia</i> have failed due to rapid shoot browning and subsequent explant death. The aim of this study was to characterize the browning process during the in vitro culture of nodal explants of this species using a combined physiological, biochemical, and structural approach. We applied a Browning Gradient Index, monitored tissue pH, quantified polyphenol oxidase (PPO) activity and total phenolic content, profiled phenolic compounds, localized PPO histochemically, and performed ultrastructural analyses. Explants of <i>G. amplexifolia</i> were compared with those of <i>G. angustifolia</i> var. bicolor, a non-browning control. The results suggest that browning in <i>G. amplexifolia</i> corresponded to an enzymatic process associated with increased PPO activity and tyrosinase-like substrate preference. This was inferred from the depletion of monophenols (e.g., ferulic and sinapic acids) and diphenols (e.g., rutin). PPO accumulation was localized in the vascular bundles of browned shoots, coinciding with structural deterioration and cellular disorganization in the stem and leaf tissues. Polyvinylpyrrolidone (1 and 2.5&#xa0;g L<sup>− 1</sup>) effectively prevented browning during the initial culture phase and activated charcoal (1&#xa0;g L<sup>− 1</sup>) reduced browning after the first subculture. Transfer frequency remained critical, with two-week intervals providing the most effective mitigation. These findings provide a detailed characterization of browning in <i>G. amplexifolia</i> and identify key factors for improving its in vitro propagation.</p>

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Oxidative browning during early in vitro shoot formation in Guadua amplexifolia (Poaceae; Bambusoideae): biochemical pathways, vascular localization, and structural disruption

  • 期刊论文

  • 发表日期：

    2026年5月9日

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  • Ana Reyes-Ferrufino,
  • Andrea Holst,
  • Andrea Irías-Mata,
  • Reinaldo Pereira-Reyes,
  • Víctor M. Jiménez

摘要

Guadua amplexifolia J. Presl, a neotropical bamboo species, is of emerging economic importance due to the physical and mechanical properties of its culms. Although protocols for in vitro culture have been developed for other bamboo species, previous attempts with G. amplexifolia have failed due to rapid shoot browning and subsequent explant death. The aim of this study was to characterize the browning process during the in vitro culture of nodal explants of this species using a combined physiological, biochemical, and structural approach. We applied a Browning Gradient Index, monitored tissue pH, quantified polyphenol oxidase (PPO) activity and total phenolic content, profiled phenolic compounds, localized PPO histochemically, and performed ultrastructural analyses. Explants of G. amplexifolia were compared with those of G. angustifolia var. bicolor, a non-browning control. The results suggest that browning in G. amplexifolia corresponded to an enzymatic process associated with increased PPO activity and tyrosinase-like substrate preference. This was inferred from the depletion of monophenols (e.g., ferulic and sinapic acids) and diphenols (e.g., rutin). PPO accumulation was localized in the vascular bundles of browned shoots, coinciding with structural deterioration and cellular disorganization in the stem and leaf tissues. Polyvinylpyrrolidone (1 and 2.5 g L− 1) effectively prevented browning during the initial culture phase and activated charcoal (1 g L− 1) reduced browning after the first subculture. Transfer frequency remained critical, with two-week intervals providing the most effective mitigation. These findings provide a detailed characterization of browning in G. amplexifolia and identify key factors for improving its in vitro propagation.