Radial growth has long been a subject of interest in tree biology research. Recent studies have brought a significant change in the understanding of some basic processes characteristic to the vascular cambium, a meristem that produces secondary vascular tissues (phloem and xylem) in woody plants. A new hypothesis regarding the mechanism of intrusive growth of the cambial initials, which has been ratified by studies of the arrangement of cambial cells, negates the influence of this apical cell growth on the expansion of the cambial circumference. Instead, it suggests that the tip of the elongating cambial initial intrudes between the tangential (periclinal) walls, rather than the radial (anticlinal) walls, of the initial(s) and its(their) derivative(s) lying ahead of the elongating cell tip. The new concept also explains the hitherto obscure mechanism of the cell event called ‘elimination of initials’. This article evaluates these new concepts of the cambial cell dynamics and offers a new interpretation for some curious events occurring in the cambial meristem in relation to the radial growth in woody plants.

径向生长长期以来一直是树木生物学研究感兴趣的主题。最近的研究使人们对维管形成层的一些基本过程特征的理解发生了重大变化，维管形成层是一种在木本植物中产生次生维管组织（韧皮部和木质部）的分生组织。关于形成层首字母侵入性生长机制的新假设已通过对形成层细胞排列的研究得到证实，否定了这种顶端细胞生长对形成层周长扩张的影响。相反，它表明伸长的形成层初始的尖端侵入切向（周）壁之间，而不是位于伸长之前的初始及其（它们的）导数的径向（背斜）壁之间细胞提示。这个新概念还解释了迄今为止被称为“消除首字母”的细胞事件的模糊机制。本文评估了形成层细胞动力学的这些新概念，并为在形成层分生组织中发生的与木本植物径向生长相关的一些奇怪事件提供了新的解释。