Evolution of extreme xeromorphic characters in wood: A study of nine evolutionary lines in Cactaceae
Evolution of extreme xeromorphic characters in wood: A study of nine evolutionary lines in Cactaceae
复制标题
DOI：
10.2307/2446308
复制
发表时间：
1998-02-01
影响因子：
3
通讯作者：
Plemons-Rodriguez, BJ
中科院分区：
文献类型：
--
作者：
Mauseth, JD;Plemons-Rodriguez, BJ
据预测，适应干旱的木材的导管比适应中湿的木材的导管更窄，出现的密度更高，出现在更大的簇中，并且在簇中具有更大的百分比。这些预测通过将适应干旱的仙人掌的几个进化系的木材结构与适应中湿的Pereskia的木材结构进行了测试，后者可能类似于仙人掌的祖先。尽管衍生仙人掌出现在水分胁迫从轻度（雨林）到严重（除仙人掌以外几乎没有植被的开阔沙漠）的栖息地中，只要植物保留具有普通纤维基质的木材，木材特性就非常均匀，并且与栖息地干旱度无关。然而，在一些进化路线中，出现了新的木材类型，其特征满足了上面列出的耐旱木材的预测。然而，传导面积（管道所占木材横截面积的比例）和估计的比电导率（每平方毫米的电导率）与枝条高度（木纤维机械支撑的需要）相关，而不是与栖息地的干旱度相关：高大的植物通过相对较少、较宽的容器输送水，从而允许大部分木材体积由纤维组成。木材较少的小型工厂使用大量窄容器而不是少量宽容器，从而实现导电安全。
Vessels of xeric-adapted woods have been predicted to be narrower than those of mesic-adapted woods, to occur at higher densities, to occur in larger clusters, and to have a greater percentage of them in clusters. These predictions were tested by comparing wood structure of several evolutionary lines of xeric-adapted cacti to that of mesic-adapted Pereskia, which probably resembles the ancestral cacti. Although derived cacti occur in habitats with water stress ranging from mild (rain forests) to severe (open deserts with little vegetation other than cacti), as long as plants retain wood with an ordinary fibrous matrix, wood characters are remarkably uniform and not correlated with habitat aridity. However, in several evolutionary lines, novel wood types occur with characters that fulfill the predictions for xeric-adapted woods listed above. However, conductive area (fraction of wood transverse-sectional area occupied by conduits) and estimated specific conductance (conductance per square millimetre) are correlated with shoot height (the need for mechanical support from xylary fibers) rather than with habitat aridity: tall plants transport water through relatively few, wide vessels, permitting much of the wood volume to consist of fibers. Small plants with Little wood use large numbers of narrow vessels rather than small numbers of wide ones, thereby achieving conductive safety.