Key message

Primary growth is less sensitive than secondary growth to water and phloem blockage in maritime pine saplings, with variations in radial growth resulting from tracheid production without altering their size.

Abstract

In plants, primary and secondary growth is regulated by internal and external factors. However, apical and cambial meristems may not respond in the same way. In this study, we disentangle the role of carbon and water availability on stem growth (primary and secondary) and on anatomical tracheid features by investigating the effect of stem girdling (phloem blockage vs. no phloem blockage) and water availability (control vs. drought) in three-year-old Pinus pinaster saplings. We found that primary growth was similar among treatments, while secondary growth was affected by both treatments. Tree ring-width increment in saplings subjected to drought corresponded to half of that on control plants, and phloem blockage enhanced ring width under guidelines soil water conditions. These differences in the radial growth resulted mainly from an increase in tracheid production, which also increased with phloem blockage (above the girdling), regardless the water regime. However, the seasonal pattern of tracheid features was mainly explained by individuals and to a less extent by the water regime and girdling. Contrasting seasonal patterns between treatments were found only on cell wall thickness, showing a faster decrease with increasing water constrains in the drought group than in the control one. The absence of treatment effects on primary growth in P. pinaster saplings suggests a trade-off between the priority in plant development and meristem sensitivity to environmental conditions.

中文翻译：

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在松树苗中，水和茎环剥对管胞数量的影响大于对管胞形状的影响

关键信息

在海松树苗中，初级生长对水和韧皮部阻塞的敏感性低于次级生长，径向生长的变化是由管胞产生而不会改变它们的大小。

抽象的

在植物中，初级和次级生长受内部和外部因素的调节。然而，顶端和形成层分生组织的反应方式可能不同。在这项研究中，我们通过调查茎环剥（韧皮部阻塞与无韧皮部阻塞）和水可用性（控制与干旱）的影响，解开碳和水可用性对茎生长（初级和次生）和解剖管胞特征的作用) 在三岁的松树中树苗。我们发现处理之间的初级生长相似，而次生生长受两种处理的影响。干旱后树苗的年轮宽度增量相当于对照植物的一半，韧皮部堵塞增加了指导土壤水分条件下的年轮宽度。径向生长的这些差异主要是由于管胞产量的增加，这也随着韧皮部堵塞（环剥上方）而增加，无论水情如何。然而，管胞特征的季节性模式主要由个人解释，在较小程度上由水情和环带解释。处理之间的对比季节性模式仅在细胞壁厚度上发现，与对照组相比，干旱组随着水分限制的增加而下降更快。P. pinaster树苗建议在植物发育的优先级和分生组织对环境条件的敏感性之间进行权衡。