Morphogenetic gradients in silver firs (Abies alba Mill.) and their plasticity
2011
Taugourdeau, Olivier | Sabatier, Sylvie-Annabel | Caraglio, Yves | Barthélémy, Daniel
Silver fir presents a great hierarchised architecture with a strict monopodial development (Massart's architectural model). Moreover silver fir presents neither polycyclism nor immediate branching (often involved in the plastic response of primary growth). Despite these limitations, silver firs present a large range of distribution: from Central Europe to Mediterranean mountains. The aim of this poster is to test the hypothesis that silver firs offset this limitation with a strong plasticity at the annual shoot scale and on needle morphology. The study was done in Mont Ventoux, a French Mediterranean mountain which provides contrasted forest environments in terms of elevation and with a marked summer drought. Quantitative traits of annual shoots of 2 years old branches (length, diameter and number of needles, dry mass) and needles (surface and dry mass) where recorded on 80 saplings growing in different light environments. Effects of tree size and architectural position of annual shoot within tree crown on measured traits were higher than any environmental fluctuation. These morphogenetic gradients are consistent with the concept of physiological age of meristems (Barthélémy & Caraglio 2007): huge effect of tree development, branching order and position. All studied traits present a significant plasticity which may be implies in the success of silver firs in the studied site. No clear hierarchy was found between the phenotypic plasticity of annual shoot plasticity and the one of needles. We can suggest that all measured traits act simultaneously during tree development and in response to environmental fluctuations ('a variational module' sensu Wagner et al 2007). (Texte intégral)
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