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Variations in leaf anatomy narrow-leafed ash trees (Fraxinus angustifolia Vahl. spp. angustifolia) in southern France : Influence of shoot type and architectural stage

Ramirez de Arellano F., Nicolini E.A., Barthélémy D.. 2004. In : Godin Christophe (ed.), Hanan Jim (ed.), Kurth Winfried (ed.), Lacointe André (ed.), Takenaka Akio (ed.), Prusinkiewicz Przemyslaw (ed.), Dejong Thedore M. (ed.), Beveridge Christine (ed.). Proceedings of the 4th International workshop on functional-structural plant models (FSPM), abstracts of papers and posters, 7-11 June 2004, Montpellier, France. Montpellier : CIRAD-AMAP, p. 48-48. International Workshop on Functional-Structural Plant Models (FSPM). 4, 2004-06-07/2004-06-11, Montpellier (France).

Tree functional-structural models often assume even behaviour throughout plant organs, but this is rarely the case in real plants. However, recent advance in computing and plant modelling enables some complex processes involved in plant development to be incorporated into fairly realistic models. Yet, many biological processes like stomatal conductance or foliage acclimation to environmental factors remain rather elusive and extensive research is still necessary in order to produce robust models. Image processing enables accurate quantitative analysis of structure - at both micro and macroscopic levels - and may provide useful information for plant modelling. The aim of the present study is to assess, by means of image processing techniques, the relative importance of different morphological and anatomical traits of Fraxinus angustifolia leaves - issued from both long and short, non ramified, shoots - in global leaf structure throughout tree development. Thus, phyllotactic arrangement, leaf length, number of leaflets per leaf, leaf mass per area (LMA), stomatal density, leaflet form, surface and lamina thickness, leaf histology (parenchyma and other tissues sectional area), where assessed in both short and long shoots for 42 individuals belonging to four different architecturally defined life stages growing in an open area. Results show that morphological features evolve throughout tree development, some of them attaining maximal values at the "young reproductive adult" stage whilst some others continue to augment well into the senescent stage. Leaf length, lamina thickness, LMA and number of leaflets per leaf belong to the first case whereas phyllotactic arrangement (proportion of 3-whorled vs. 2-whorled shoots), leaflet size and stomatal density belong to the second. Most measured parameters tend to show slightly higher values for leaves issued from long shoots. On the other hand, histological features like the relative sectional areas of palisade and spongy paren

Mots-clés : fraxinus; anatomie végétale; pousse; ramification; développement biologique; morphogénèse; imagerie; phyllotaxie; architecture des arbres

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