Puntieri J G, Souza M S, Brion C, Mazzini C, Barthelemy D
Department of Botany, Universidad Nacional del Comahue, Quintral 1250, 8400 Bariloche, Argentina.
Ann Bot. 2003 Oct;92(4):589-99. doi: 10.1093/aob/mcg175. Epub 2003 Aug 21.
An analysis was carried out on the length, diameter and number of leaves, and the ratios between these variables for current-year growth units (sibling growth units) derived from different nodes of previous-year growth units (parent growth units) of young Nothofagus dombeyi and Nothofagus pumilio trees. Changes in sibling growth unit length, diameter, and number of leaves with position on the parent growth unit were assessed. In both species, sibling-growth unit morphology varied according to both the axis type of the parent growth unit and the position of the sibling growth unit on its parent growth unit. For the largest parent growth units, the length, diameter and number of leaves of their sibling growth units decreased from distal to proximal positions on the parent growth unit. Distal sibling growth units had a more slender stem and longer internodes than proximal sibling growth units. Sibling growth units in equivalent positions tended to have a more slender stem for N. dombeyi than for N. pumilio. Long main-branch growth units of N. pumilio had longer internodes than those of N. dombeyi; the converse was true for shorter growth units. The growth unit diameter/leaf number ratio was consistently higher for N. pumilio than for N. dombeyi. Nothofagus pumilio axes would go through a faster transition from an 'exploring' morphology to an 'exploiting' morphology than N. dombeyi axes. Within- and between-species variations in growth unit morphology should be considered when assessing the adaptive value of the branching pattern of plants.
对新生长的假山毛榉和矮假山毛榉树前一年生生长单元（母生长单元）不同节点衍生的当年生长单元（同胞生长单元）的叶长、叶直径、叶数量以及这些变量之间的比率进行了分析。评估了同胞生长单元的长度、直径和叶数量随其在母生长单元上位置的变化。在这两个物种中，同胞生长单元的形态既随母生长单元的轴类型而变化，也随其在母生长单元上的位置而变化。对于最大的母生长单元，其同胞生长单元的长度、直径和叶数量从母生长单元的远端到近端位置逐渐减少。远端同胞生长单元的茎比近端同胞生长单元更细长，节间更长。在相同位置的同胞生长单元中，假山毛榉的茎往往比矮假山毛榉的更细长。矮假山毛榉的长主枝生长单元的节间比假山毛榉的长；对于较短的生长单元则相反。矮假山毛榉的生长单元直径/叶数量比始终高于假山毛榉。矮假山毛榉的轴比假山毛榉的轴从“探索”形态向“利用”形态的转变更快。在评估植物分枝模式的适应性价值时，应考虑生长单元形态在种内和种间的差异。
