Callus induction is an important stage in micropropagation. In this study, embryos, cotyledons, and hypocotyls of tree peony (Paeonia ostii ‘Fengdan’) were used as explants to induce callus formation. Callus induction was largely influenced by the medium, plant growth regulator, and explant. All combinations of the medium and plant growth regulator were conducive to callus induction from zygotic embryos, where the ratio of explants with callus induction was very high in all of the combinations. The greatest ratio of explants with callus induction from the cotyledon explants was found on Woody Plant Medium (WPM) or Murashige and Skoog (MS) medium supplemented with both 0.5 mg L−1 thidiazuron (TDZ) and either 0.5 mg L−1 2,4-dichlorophenoxyacetic acid (2,4-D) or 0.5 mg L−1 1-naphthaleneacetic acid (NAA), and on the WPM containing 0.5 mg L−1 NAA and 0.5 mg L−1 6-benzylaminopurine (BA). The ratio of explants with callus induced from the hypocotyl explants was the greatest on either MS medium or WPM supplemented with both 0.5 mg L−1 2,4-D and 0.5 mg L−1 TDZ. In contrast, a combination of 0.5 mg L−1 2,4-D and 0.5 mg L−1 TDZ, or 0.5 mg L−1 NAA and 0.5 mg L−1 TDZ was highly likely to cause a browning problem during culture. For browning suppression, calcium chloride (CaCl2), polyvinyl pyrrolidone (PVP), gallic acid, and caffeic acid were much more effective than other reagents. The efficacy on browning suppression was concentration-dependent, and the best results were obtained at a concentration of 4.0 mg L−1 CaCl2, 1.0–2.0 g L−1 PVP, 0.5–1.0 mg L−1 gallic acid, and 0.5–1.0 mg L−1 caffeic acid, respectively. In summary, callus formation was successfully induced from the zygotic embryo, cotyledon, and hypocotyl explants, and callus browning was effectively suppressed by caffeic acid (0.5–1.0 mg L−1), gallic acid (1.0 mg L−1), CaCl2 (4.0 mg L−1), and PVP (1.0 g L−1).

中文翻译：

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牡丹芍药‘凤丹’愈伤组织诱导及褐变抑制

愈伤组织诱导是微繁殖的一个重要阶段。在这项研究中，牡丹 (Paeonia ostii 'Fengdan') 的胚胎、子叶和下胚轴用作外植体以诱导愈伤组织形成。愈伤组织诱导在很大程度上受培养基、植物生长调节剂和外植体的影响。培养基和植物生长调节剂的所有组合都有利于合子胚的愈伤组织诱导，其中所有组合中具有愈伤组织诱导的外植体比例都非常高。在木本植物培养基 (WPM) 或 Murashige 和 Skoog (MS) 培养基上发现了来自子叶外植体的愈伤组织诱导的最大比例，并补充了 0.5 mg L-1 噻二唑隆 (TDZ) 和 0.5 mg L-1 2， 4-二氯苯氧基乙酸 (2,4-D) 或 0.5 mg L-1 1-萘乙酸 (NAA)，并在含有 0.5 mg L-1 NAA 和 0 的 WPM 上。5 毫克 L-1 6-苄基氨基嘌呤 (BA)。从下胚轴外植体诱导的愈伤组织的外植体比例在 MS 培养基或 WPM 上都最大，补充有 0.5 mg L-1 2,4-D 和 0.5 mg L-1 TDZ。相比之下，0.5 mg L-1 2,4-D 和 0.5 mg L-1 TDZ，或 0.5 mg L-1 NAA 和 0.5 mg L-1 TDZ 的组合极有可能在培养过程中引起褐变问题。对于褐变抑制，氯化钙 (CaCl2)、聚乙烯吡咯烷酮 (PVP)、没食子酸和咖啡酸比其他试剂更有效。抑制褐变的功效是浓度依赖性的，最好的结果是在浓度为 4.0 mg L-1 CaCl2、1.0-2.0 g L-1 PVP、0.5-1.0 mg L-1 没食子酸和 0.5-1.0 mg L−1 咖啡酸，分别。总之，从合子胚、子叶、