Apple shoot architecture: evidence for strong variability of bud size and composition and hydraulics within a branching zone.
* In the apple tree (Malus domestica), shoot architecture - the distribution of lateral bud types and growth along the parent shoot - has been extensively investigated. The distal zone of a shoot is characterized by a high proportion of vegetative or floral axillary branches mixed with latent buds and aborted laterals. The hypothesis tested here was that bud development was related to hydraulic conductance of the sap pathway to the bud, independently of an acrotonic (proximal vs distal) effect. * The distal zone of 1-yr-old shoots was studied on five cultivars for bud size and composition (number of appendages) and hydraulic conductance before bud burst. * Bud size, composition and hydraulic conductance were highly variable for all cultivars. A positive correlation was demonstrated between both the number of cataphylls and green-leaf primordia, and hydraulic conductance. Cultivar and bud size affected the intercept of these relationships more than the slope, suggesting similar scaling between these variables, but different hydraulic efficiencies. A great proportion of small buds were also characterized by null values of hydraulic conductance. * This study suggests that hydraulically mediated competition exists between adjacent buds within the same branching zone, prefiguring the variability of lateral types in the following growing season. It is hypothesized that this developmental patterning is driven by hydraulic characteristics of the whole metamer, including the subtending leaf, during bud development.
Lauri
Pierre-Éric
PÉ
INRA, UMR DAP, #1098, Équipe AFEF, 2 Place P. Viala, 34060 Montpellier cedex 1, France.
Bourdel
Guillaume
G
INRA, UMR DAP, #1098, Équipe AFEF, 2 Place P. Viala, 34060 Montpellier cedex 1, France.
Trottier
Catherine
C
Université Montpellier II, UMR I3M, #5149, Équipe 'Probabilités et Statistique', 34095 Montpellier cedex 5, France.
Cochard
Hervé
H
INRA, UMR PIAF, #547, Site de Crouël, 234 Avenue du Brézet, 63100 Clermont-Ferrand, France.
D035264:Flowers / Q000033:anatomy & histology*; D027845:Malus / Q000502:physiology*; D009929:Organ Size; D053147:Plant Exudates / Q000502:physiology; D018515:Plant Leaves / Q000502:physiology; D018520:Plant Shoots / Q000502:physiology*; D052584:Xylem / Q000502:physiology
D053147:Plant Exudates