尺寸是否与时间有关？木质部发育时间与细胞特征的关系。
Is size an issue of time? Relationship between the duration of xylem development and cell traits.
机构信息
Département des Sciences fondamentales, Université du Québec à Chicoutimi, Chicoutimi, QC, Canada.
Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.
出版信息
Ann Bot. 2019 Jul 8;123(7):1257-1265. doi: 10.1093/aob/mcz032.
BACKGROUND AND AIMS
Secondary growth is a process related to the formation of new cells that increase in size and wall thickness during xylogenesis. Temporal dynamics of wood formation influence cell traits, in turn affecting cell patterns across the tree ring. We verified the hypothesis that cell diameter and cell wall thickness are positively correlated with the duration of their differentiation phases.
METHODS
Histological sections were produced by microcores to assess the periods of cell differentiation in black spruce [Picea mariana (Mill.) B.S.P.]. Samples were collected weekly between 2002 and 2016 from a total of 50 trees in five sites along a latitudinal gradient in Quebec (Canada). The intra-annual temporal dynamics of cell differentiation were estimated at a daily scale, and the relationships between cell traits and duration of differentiation were fitted using a modified von Bertalanffy growth equation.
KEY RESULTS
At all sites, larger cell diameters and cell wall thicknesses were observed in cells that experienced a longer period of differentiation. The relationship was a non-linear, decreasing trend that occasionally resulted in a clear asymptote. Overall, secondary wall deposition lasted longer than cell enlargement. Earlywood cells underwent an enlargement phase that lasted for 12 d on average, while secondary wall thickness lasted 15 d. Enlargement in latewood cells averaged 7 d and secondary wall deposition occurred over an average of 27 d.
CONCLUSIONS
Cell size across the tree ring is closely connected to the temporal dynamics of cell formation. Similar relationships were observed among the five study sites, indicating shared xylem formation dynamics across the entire latitudinal distribution of the species.The duration of cell differentiation is a key factor involved in cell growth and wall thickening of xylem, thereby determining the spatial variation of cell traits across the tree ring.
背景与目的
次生生长是一个与新细胞形成相关的过程，这些细胞在木质部形成过程中会增大和增厚细胞壁。木材形成的时间动态会影响细胞特征，进而影响整个树轮中的细胞模式。我们验证了这样一个假设，即细胞直径和细胞壁厚度与它们分化阶段的持续时间呈正相关。
方法
通过微芯木制作组织切片，以评估黑云杉（Picea mariana (Mill.) B.S.P.）的细胞分化周期。在 2002 年至 2016 年期间，从魁北克（加拿大）五个地点的总共 50 棵树上每周采集样本。在每日尺度上估计细胞分化的年内时间动态，并使用修正的 von Bertalanffy 生长方程拟合细胞特征与分化持续时间之间的关系。
主要结果
在所有地点，分化时间较长的细胞具有较大的细胞直径和细胞壁厚度。这种关系是非线性的，呈递减趋势，偶尔会出现明显的渐近线。总的来说，次生壁的沉积持续时间长于细胞的扩大。早材细胞经历了一个持续 12 天的扩大阶段，而次生壁厚度持续 15 天。晚材细胞的扩大平均持续 7 天，次生壁沉积持续平均 27 天。
结论
树轮中的细胞大小与细胞形成的时间动态密切相关。在五个研究地点也观察到了类似的关系，这表明该物种在整个纬度分布范围内具有相似的木质部形成动态。细胞分化的持续时间是细胞生长和木质部细胞壁增厚的关键因素，从而决定了细胞特征在树轮中的空间变化。
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