Uggla C, Magel E, Moritz T, Sundberg B
Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden.
Plant Physiol. 2001 Apr;125(4):2029-39. doi: 10.1104/pp.125.4.2029.
In temperate regions the annual pattern of wood development is characterized by the formation of radially narrow and thick walled latewood cells. This takes place at the later part of the growing season when cambial cell division declines. To gain new insight into the regulation of this process, micro-analytical techniques were used to visualize the distribution of indole-3-acetic acid (IAA), soluble carbohydrates, and activities of sucrose (Suc)-metabolizing enzymes across the cambial region tissues in Scots pine (Pinus sylvestris). The total amount of IAA in the cambial region did not change with latewood initiation. But its radial distribution pattern was altered, resulting in an increased concentration in the cambial meristem and its recent derivatives. Thus, initiation of latewood formation and cessation of cambial cell division is not a consequence of decreased IAA concentrations in dividing and expanding cells. Rather, IAA most likely has a role in defining the altered developmental pattern associated with latewood formation. Carbohydrates and enzyme activities showed distinctive radial distribution patterns. Suc peaked in the phloem and decreased sharply to low levels across the cambial zone, whereas fructose and glucose reached their highest levels in the maturing tracheids. Suc synthase was the dominating Suc cleaving enzyme with a peak in the secondary wall-forming tracheids and in the phloem. Soluble acid invertase peaked in dividing and expanding cells. Suc-phosphate synthase had its highest activities in the phloem. Activities of cell wall bound invertase were low. The absence of major seasonal variations indicates that carbohydrate availability is not a trigger for latewood initiation. However, steep concentration gradients of the sugars suggest a role for sugar signaling in vascular development.
在温带地区，木材发育的年度模式以径向狭窄且壁厚的晚材细胞形成为特征。这一过程发生在生长季节后期，此时形成层细胞分裂减少。为了深入了解这一过程的调控机制，运用微观分析技术来观察吲哚 - 3 - 乙酸（IAA）、可溶性碳水化合物以及蔗糖（Suc）代谢酶活性在苏格兰松（Pinus sylvestris）形成层区域组织中的分布情况。形成层区域内IAA的总量在晚材开始形成时并未改变。但其径向分布模式发生了改变，导致形成层分生组织及其最近衍生细胞中的浓度增加。因此，晚材形成的起始和形成层细胞分裂的停止并非是分裂和扩展细胞中IAA浓度降低的结果。相反，IAA很可能在定义与晚材形成相关的发育模式改变中发挥作用。碳水化合物和酶活性呈现出独特的径向分布模式。蔗糖在韧皮部达到峰值，并在整个形成层区域急剧下降至低水平，而果糖和葡萄糖在成熟的管胞中达到最高水平。蔗糖合酶是主要的蔗糖裂解酶，在次生壁形成的管胞和韧皮部中达到峰值。可溶性酸性转化酶在分裂和扩展细胞中达到峰值。蔗糖磷酸合酶在韧皮部具有最高活性。细胞壁结合转化酶的活性较低。主要季节变化的缺失表明碳水化合物的可利用性并非晚材起始的触发因素。然而，糖的陡峭浓度梯度表明糖信号在维管发育中发挥作用。
