Costes E, García-Villanueva E, Jourdan C, Regnard J L, Guédon Y
UMR BEPC, Architecture et Fonctionnement des Espèces Fruitières, INRA-2 Place Viala, 34060 Montpellier Cedex 1, France.
Ann Bot. 2006 Jan;97(1):85-96. doi: 10.1093/aob/mcj003. Epub 2005 Oct 31.
In several species exhibiting a rhythmic aerial growth, the existence of an alternation between root and shoot growth has been demonstrated. The present study aims to investigate the respective involvement of the emergence of new organs and their elongation in relation to this phenomenon and its possible genotypic variation in young apple plants.
Two apple varieties, X6407 (recently named 'Ariane') and X3305 ('Chantecler' x 'Baujade'), were compared. Five plants per variety, issued from in vitro culture, were observed in minirhizotrons over 4 months. For each plant, root emergence and growth were observed twice per week. Growth rates were calculated for all roots with more than two segments and the branching density was calculated on primary roots. On the aerial part, the number of leaves, leaf area and total shoot length were observed weekly.
No significant difference was observed between varieties in any of the final characteristics of aerial growth. Increase in leaf area and shoot length exhibited a 3-week rhythm in X3305 while a weaker signal was observed in Ariane. The primary root growth rate was homogeneous between the plants and likewise between the varieties, while their branching density differed significantly. Secondary roots emerged rhythmically, with a 3-week and a 2-week rhythm, respectively, in X3305 and 'Ariane'. Despite a high intra-variety variability, significant differences were observed between varieties in the secondary root life span and mean length. A synchronism between leaf emergence and primary root growth was highlighted in both varieties, while an opposition phase was observed between leaf area increments and secondary root emergence in X3305 only.
A biological model of dynamics that summarizes the interactions between processes and includes the assumption of a feedback effect of lateral root emergence on leaf emergence is proposed.
在一些呈现出节律性地上部生长的物种中，已证实存在根和地上部生长的交替现象。本研究旨在探究新器官的出现及其伸长在这一现象中的各自作用，以及其在苹果幼苗中的可能基因型变异。
比较了两个苹果品种，X6407（最近命名为“Ariane”）和X3305（“Chantecler”דBaujade”）。从每个品种的离体培养植株中选取5株，在微型根际管中观察4个月。对于每株植物，每周观察两次根的出现和生长情况。计算所有具有两段以上根段的根的生长速率，并计算初生根上的分支密度。在地上部分，每周观察叶片数量、叶面积和地上部总长度。
在地上部生长的任何最终特征方面，两个品种之间均未观察到显著差异。X3305中叶面积和地上部长度的增加呈现出3周的节律，而“Ariane”中观察到的信号较弱。植株间以及品种间初生根的生长速率是均匀的，但其分支密度存在显著差异。次生根有节律地出现，在X3305和“Ariane”中分别呈现出3周和2周的节律。尽管品种内存在较高的变异性，但在次生根寿命和平均长度方面，品种间观察到了显著差异。两个品种中均突出显示了叶片出现与初生根生长之间的同步性，而仅在X3305中观察到叶面积增加与次生根出现之间的相反阶段。
提出了一个动力学生物学模型，该模型总结了各过程之间的相互作用，并包括侧根出现对叶片出现的反馈效应的假设。
