"Secondary stem lengthening" in the palm Iriartea deltoidea (Arecaceae) provides an efficient and novel method for height growth in a tree form.
"Secondary stem lengthening" in the palm Iriartea deltoidea (Arecaceae) provides an efficient and novel method for height growth in a tree form.
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棕榈树 Iriartea deltoidea（槟榔科）的“二次茎延长”提供了一种有效且新颖的树高生长方法。
DOI：
10.3732/ajb.1100523
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发表时间：
2012
影响因子：
3
通讯作者：
N. Phillips
中科院分区：
文献类型：
--
作者：
H. Renninger;N. Phillips
研究前提
虽然传统上认为，所有的高度增长发生在树的顶端分生组织，在棕榈Iriartea deltoidea节间长度的连续测量表明，茎伸长后很长一段时间的组织分化和远低于顶端分生组织。这一观察结果很难与这样一个事实相一致，即无论是导水导管还是运输糖的筛管细胞在分化后都不能伸长。然而，棕榈中的维管束在茎内形成螺旋，如果螺旋“拉直”，理论上可以延长。
方法
我们在中小型棕榈树上标记了节间的延伸，并测量了它们的长度超过2年。此外，我们还收集了节间短的小型棕榈和节间长的大型棕榈的材料，并制作了横截面以确定茎内维管束的角度。
关键成果
我们发现，茎延长（超过2年的12%）以下的顶端分生组织在小型和中型的棕榈树和小棕榈树的维管束的螺旋角显着大于在大棕榈树的基础上，表明矫直的螺旋。
结论
这些结果代表了第一次确定的“二次延长”的树干，以及最有效的方法，高度增长的碳投资。同样，茎的伸长允许棕榈树表现出可塑性的高度增长率更快的增长时，短暂的冠层间隙是本比他们将与单独的顶端生长。
PREMISE OF THE STUDY
Although traditionally assumed that all height growth in trees occurs at apical meristems, sequential measurement of internode lengths in the palm Iriartea deltoidea suggested that stems were lengthening long after the differentiation of tissues and far below the apical meristem. This observation is difficult to reconcile with the fact that neither the water-conducting vessels nor the sugar-transporting sieve tube cells are capable of lengthening after differentiation. However, the vascular bundles in palms form a spiral within the stem and could theoretically lengthen if the spiral "straightened".
METHODS
We marked stretches of internodes on small and medium-sized palms and measured their lengths over 2 years. Additionally, we collected material from small palms with short internodes and large palms with long internodes and made cross sections to determine the angle of vascular bundles within stems.
KEY RESULTS
We found that stems lengthened (up to 12% over 2 years) below the apical meristem in small and medium-sized palms and that the spiral angle in vascular bundles of small palms was significantly larger than at the base of large palms indicating a straightening of the spiral.
CONCLUSIONS
These results represent the first determination of "secondary lengthening" in tree stems as well as the most efficient method for height growth in terms of carbon investment. Likewise, elongation of stems allows palms to exhibit plasticity in height growth rates for more rapid growth when short-lived canopy gaps are present than they would have with apical growth alone.