AOBPreview originally published online on October 31, 2005
Annals of Botany 2006 97(1):85-96; doi:10.1093/aob/mcj003
Co-ordinated Growth between Aerial and Root Systems in Young Apple Plants Issued from in vitro Culture
1 UMR BEPC, Architecture et Fonctionnement des Espèces Fruitières, INRA—2 Place Viala, 34060 Montpellier Cedex 1, France, 2 CIRAD TA 80/01, Avenue Agropolis, 34398 Montpellier Cedex 5, France and 3 UMR AMAP, CIRAD TA40/PS2, 34398 Montpellier Cedex 5, France
* For correspondence. E-mail costes{at}ensam.inra.fr
Received: 11 May 2005 Returned for revision: 23 August 2005 Accepted: 20 September 2005 Published electronically: 31 October 2005
• Background and Aims 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.
• Methods 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.
• Key Results 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.
• Conclusion 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.
Key words: Plant architecture, root–shoot equilibrium, rhythmic growth, synchronism, time series