Tree Physiology Advance Access originally published online on August 20, 2009
Tree Physiology 2009 29(10):1223-1235; doi:10.1093/treephys/tpp061
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Intra-annual cambial activity and carbon availability in stem of poplar
1 Département des Sciences Fondamentales, Université du Québec à Chicoutimi, 555 Boulevard de l’Université, Chicoutimi, QC, Canada
2 Corresponding author (annie_deslauriers{at}uqac.ca)
3 Dipartimento Territorio e Sistemi Agro-Forestali, Università degli Studi di Padova, viale dell’Università 16, 35020 Legnaro, PD, Italy
4 Laboratorio Xilogenesi, Istituto Valorizzazione Legno e Specie Arboree, IVaLSA-CNR, via Madonna del Piano, 50019 Sesto Fiorentino, FI, Italy
5 Unità di Ricerca per le Produzioni Legnose Fuori Foresta, CRA, strada per Frassineto, 15033 Casale Monferrato, AL, Italy
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Abstract |
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Cambial activity is influenced by many environmental and physiological factors and among them, carbon acts as a source of energy for the growing meristems. This work has focused on the intra-annual stem growth of poplar compared with the carbon available for xylogenesis processes in cambium and outer wood. The major stages of xylem production and differentiation in two poplar genotypes with different growth performances were considered. Monitoring of stem growth and leaf phenology combined with starch, nonstructural soluble sugars and water content in the stem was conducted from February to November 2006 in Populus x canadensis Moench ‘I-214’ and Populus deltoides Marsh. ‘Dvina’. Anatomical analyses of wood formation were performed by measuring the width of the zones with differentiating and mature xylem. At the end of the growing period, wood density was assessed by microdensity analyses. Xylem differentiation at the top of the tree started at the beginning of April for both genotypes and proceeded down the stem at about 0.5 m day–1, occurring almost at the same time as leaf opening. The rate of growth and wood density was superior in Dvina, but this higher productivity could not be explained by differences in the number of cambial initials and the duration of xylogenesis. However, the most productive poplar genotype showed higher glucose, fructose and sucrose content in the outer wood. The nonstructural soluble sugars available in the cambial zone followed the intra-annual pattern of xylem formation, with a higher concentration when the growth rate was maximum. The accumulations of nonstructural soluble sugars at a certain time during stem growth corresponded with a higher carbon availability to the actively growing meristems in the stem.
Keywords: carbohydrates, cell differentiation, phenology, wood density
Received March 16, 2009; Accepted July 1, 2009