Main conclusion Shoot tip necrosis is a physiological condition that negatively impacts the growth and development of in vitro plant shoot cultures across a wide range of species. Abstract Shoot tip necrosis is a physiological condition and disorder that can arise in plantlets or shoots in vitro that results in death of the shoot tip. This condition, which can spread basipetally and affect the emergence of axillary shoots from buds lower down the stem, is due to the cessation of apical dominance. STN can occur at both shoot multiplication and rooting stages. One of the most common factors that cause STN is nutrient deficiency or imbalance. Moreover, the presence or absence of plant growth regulators (auxins or cytokinins) at specific developmental stages may impact STN. The cytokinin to auxin ratio within an in vitro plant can be modified by varying the concentration of cytokinins used in the culture medium. The supply of nutrients to in vitro shoots or plantlets might also affect their hormonal balance, thus modifying the occurrence of STN. High relative humidity within culture vessels and hyperhydricity are associated with STN. An adequate supply of calcium as the divalent cation (Ca2+) can hinder STN by inhibiting the accumulation of phenolic compounds and thus programmed cell death. Moreover, the level of Ca2+ affects auxin transport and ethylene production, and higher ethylene production, which can occur as a result of high relative humidity in or poor ventilation of the in vitro culture vessel, induces STN. High relative humidity can decrease the mobility of Ca2+ within a plant, resulting in Ca2+ deficiency and STN. STN of in vitro shoots or plantlets can be halted or reversed by altering the basal medium, mainly the concentration of Ca2+, adjusting the levels of auxins or cytokinins, or modifying culture conditions. This review examines the literature related to STN, seeks to discover the associated factors and relations between them, proposes practical solutions, and attempts to better understand the mechanism(s) underlying this condition in vitro. Electronic supplementary material The online version of this article (10.1007/s00425-020-03449-4) contains supplementary material, which is available to authorized users.

中文翻译：

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体外植物培养的芽尖坏死：重新评估可能的原因和解决方案

主要结论 芽尖坏死是一种生理状况，会对多种物种的体外植物芽培养的生长和发育产生负面影响。摘要 芽尖坏死是一种生理状况和疾病，可在试管苗或芽中出现，导致芽尖死亡。这种情况可以向基部蔓延并影响从茎下部芽的腋芽的出现，这是由于顶端优势的停止。STN 可以发生在枝条增殖和生根阶段。导致 STN 的最常见因素之一是营养缺乏或不平衡。此外，在特定发育阶段是否存在植物生长调节剂（生长素或细胞分裂素）可能会影响 STN。可以通过改变培养基中使用的细胞分裂素浓度来改变体外植物中细胞分裂素与生长素的比例。向体外芽或小植株提供营养也可能影响其激素平衡，从而改变 STN 的发生。培养容器内的高相对湿度和过度含水与 STN 相关。钙作为二价阳离子 (Ca2+) 的充足供应可以通过抑制酚类化合物的积累和程序性细胞死亡来阻碍 STN。此外，Ca2+ 水平会影响生长素转运和乙烯生产，而较高的乙烯生产可能是由于体外培养容器中相对湿度高或通风不良而导致的 STN。高相对湿度会降低植物内 Ca2+ 的流动性，导致Ca2+缺乏和STN。通过改变基础培养基，主要是Ca2+浓度，调整生长素或细胞分裂素的水平，或改变培养条件，可以停止或逆转离体芽或小植株的STN。这篇综述检查了与 STN 相关的文献，试图发现相关因素和它们之间的关系，提出切实可行的解决方案，并试图更好地了解这种情况的体外机制。电子补充材料 本文的在线版本 (10.1007/s00425-020-03449-4) 包含补充材料，可供授权用户使用。或修改培养条件。这篇综述检查了与 STN 相关的文献，试图发现相关因素和它们之间的关系，提出切实可行的解决方案，并试图更好地了解这种情况的体外机制。电子补充材料 本文的在线版本 (10.1007/s00425-020-03449-4) 包含补充材料，可供授权用户使用。或修改培养条件。这篇综述检查了与 STN 相关的文献，试图发现相关因素和它们之间的关系，提出切实可行的解决方案，并试图在体外更好地理解这种情况的机制。电子补充材料 本文的在线版本 (10.1007/s00425-020-03449-4) 包含补充材料，可供授权用户使用。