Development of the Vascular Cambium of Taxodium ascendens and Its Seasonal Activities in Subtropical China
Development of the Vascular Cambium of Taxodium ascendens and Its Seasonal Activities in Subtropical China
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DOI：
10.3390/f14061071
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发表时间：
2023-05
期刊：
影响因子：
2.9
通讯作者：
You-ming Xu;Cong Liu;Han Lin;Kunxi Wang;Zhuang Han
中科院分区：
文献类型：
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作者：
You-ming Xu;Cong Liu;Han Lin;Kunxi Wang;Zhuang Han
维管形成层是广泛且永久的次生分生组织，其周生分裂的木细胞产物通常向两个方向贡献并排列成树木的放射状排列。形成层活动是木材生产的起源。紫杉是我国的外来物种，其顶端分生组织和形成层活性尚不清楚，导致对其木材的形成和改良缺乏了解。因此，我们通过研究形成层活动来解决这一知识差距。为了进行研究，我们在 2017 年 2 月至 2018 年 3 月期间收集了五棵 30 年树龄的健康树木的树枝。解剖学将其顶端分生组织解读为柳杉-冷杉类型。原形成层出现在叶原基之后，从一岁芽横向观察，最初呈现出五个裂片。顶端下方的原形成层首先分化为原韧皮部，然后向内部分化为原木质部。这意味着原木质部分化晚于原韧皮部。休眠后，维管形成层开始活跃，从2017年4月上旬开始，晚于芽分化。 2017年7月25日，形成层区有9-10个未成熟的木质部细胞层。木质部的起始和终止都先于韧皮部的起始和终止。直到2017年10月10日，几乎没有发现未成熟元件，表明细胞从活动状态转变为休眠状态。 2017年11月15日，形成层含有3-4个呈放射状排列的细胞，这表明形成层处于休眠状态，直到明年春天。此外，随着形成层区细胞层数和细胞裂变的增加，未成熟木质部成分也增加。 T. ascendens 的生长模式表明，形成层活动具有很强的季节性，并且依赖于非生物条件的变化。因此，该物种的木材形成将随着气候模式的变化而显着改变。这些增强了我们对树木生长科学、木材形成、木材结构、木材特性变化和树木育种中木材改良的理解。
The vascular cambium is an extensive and permanent secondary meristem with wood cells products of periclinal divisions commonly contributed to two directions and arranged in radial files of trees. Cambium activity is the origin of timber production. Taxodium ascendens Brongn is an exotic species in China, and its apical meristem and cambial activity are still elusive, resulting in a lack of understanding about its wood formation and improvement. We thus addressed this knowledge gap by studying Cambium activity. For studying, twigs from five 30-year-old healthy trees were collected between February-2017 and March-2018. Anatomy deciphered its apical meristem with a Cryptomeria–Abies type. The procambium appeared after leaf primordium and initially presented five lobes as observed transversely from a one-year-old shoot. The procambium under the apical differentiated into protophloem first and then protoxylem toward the inside. It means that protoxylem differentiated later than protophloem did. After dormancy, the vascular cambium began to be active, starting in early April 2017, which was later than shoot differentiation. On 25 July 2017, the cambial zone had 9–10 immature xylem cell layers. Both initiation and cessation of the xylem preceded that of the phloem. Until 10 October 2017, few immature elements were found, indicating the translation of cells from activity to dormancy. On 15 November 2017, the cambium contained 3–4 cells in radial rows, which demonstrated the dormancy of the cambium until next spring. Furthermore, immature xylem elements increased as cell layers in the cambium zone and cell fission increased. The growth pattern of T. ascendens revealed that cambial activity is highly seasonal and dependent on changes in abiotic conditions. Thus, the wood formation in the species will be significantly altered in a changing climatic pattern. These enhance our understanding of tree growth science, wood formation, wood structure, wood properties variation and wood improvement in tree breeding.