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Epicormic shoots in plant architecture
epiphenomenon or general habit ?
Yves Caraglio, Eric Nicolini, Claude Edelin, Claire Atger, Tristan Charles-Dominique
Tree epicormics and related aspects Importance to ecology, forest management and tree care
September 14th - 17th, 2017 Nancy
AMAP joint research unit botAny and Modelling of Plant Architecture and vegetation
Epicormic branch => traumatic event ?
• Kozlowski, 1971 “Sudden and excessive exposure of trees often results in stimulation of dormant buds on the main stem or branches to produce epicormic shoots…”
• Traumatic reiteration: delayed reiteration
• Particular branching process ?
Plant Architecture
Bud activation during plant development – Immediate and/or delayed branching
• « Expected events » – Sequential branching – Contribution to 3D spatial occupancy
Plant Architecture
• Epicormic potential – Where ?
• Mainly waiting zones ! – Limit of growth unit – Base of delayed branches
» not on immediate branching – Accessory meristems
?
Plant Architecture
• Epicormic potential – When ?
• A great delay, » sometimes infinite…
– On old stem
• Unpredictable… – Lack of knowledge
» secondary growth, » hormonal signal, » carbohydrates content…
epicormics
height
ring width
Photo Sabatier
Nicolini, 1997
Particular Growth model • Activation of meristems after 4-7 years
– Prévost’s model • Paulownia imperialis
Epicormic branches expression
• During plant life cycle – Establishment growth
– Branching system bigger and more and more complex according time
– Epicormic buds at the basal part of successive stem
1
2 3
Rosa spp. (Rosaceae)
Epicormic branches expression
• During plant life cycle – Bush growth form
• Axis basitony – Epicormic buds – Life-long expression
15y 7y
3y
1y
Epicormic branches expression
• During plant life cycle – Scandent growth form
• Stack of bending axes – Epicormic buds mobilized on
external part of the curvature
Maclura cochinensis (Moraceae)
Picea excelsa (Pinaceae)
Platanus hybrida (Platanaceae)
Branch and crown die back
• Partial delayed reiteration – Spatial exploitation
Araucaria spp. (Araucariaceae)
Abies balsamea (Pinaceae)
Branch mortality
• Lateral axis senescence – Location – Origin
Epicormics from resting meristems of winter bud scars scale
Epicormics from resting meristem on lateral bud scar scales sequential branches epicormics
Senescence
• On old trees – sequential crown branching ceases… – branching still occurs through epicormics – we don’t predict when, but we know where
Pinus nigra (Pinaceae)
Chestnut tree
Pinus aristata
Tree resilience!
• Long life cycle,…eternity – A specific strategy – Low growth rate
– Avoiding individual mortality
• New individual, root autonomy
Photo Barthélémy
What should be considered as epicormics ?
• Do we consider only preventitious buds ? – Adventitious buds are considered in main papers – Epicormic bud : extension to all dormant buds (Meier,
Busgen)
• If we refer to « epicormic » term – Only localisation : on leafy axes…
• So what about root expression
– Accessory roots (monocot) – Root sucker…
Sequential Roots – Lateral roots
• Pericycle activation • Meristem initiation • Emergence or not… dormant root ?
Epicormic roots
• Jenik uses this term • What kind of reality ?
– New lateral root on old root • Traumatic response… • Included in plant architecture
– i.e. Platanus spp.
X
Dormant root ?
Photos Atger Epicormic roots
Origin of epicormic branches • Great diversity
– Actual groups • Monocot, Cycads
– Fossil groups • Progymnosperms
• Mecanism
– Bud survival
• Evolution – First expression – Radiation
Archaeopteris (Progymnospermes, Archaeopteridales) Dévonien Supérieur -365 MA
Epicormic trace Branch trace
Meyer-Berthaud et al. 2000
Cordyline sp.
Encephalarctos sp..
Epicormic branches for ever !
• In plant architecture – sequential branching (immediate or delayed) – differed branching (epicormics)
• All along plant life epicormic expression contribute to plant architecture – Not only a stress response – great contribution during senescence
• Branch level • Tree level
Research topics
• Epicormic life – How long can survive a meristem (some studies) – How can it survive (well documented on stem)
• Dynamics of such epicormic during plant development – How plant with immediate branch can react ? – Distribution of bud banks
• Proventitious , accessory, adventitious – Diversity and Ecological significance
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