Growth dynamics and morphology of annual shoots, according to their architectural position, in young Cedrus atlantica (Endl.) Manetti ex Carriere (Pinaceae)

The influence of shoot architectural position on growth and branching pattern of young Cedrus atlantica (Endl.) Manetti ex Carriere trees were studied. Extension growth and type of axillary products (lateral bud, sylleptic short or long shoots) of annual shoots of increasing branching order (main stem, branches and branchlets) were recorded weekly during the 1993 growing season. Annual final shoot length, duration of extension, and maximum extension rate decreased with increasing branching order. Sylleptic axillary shoots occurred only on annual shoots of the main stem and branches and were produced when extension rate was at its highest. Differences in growth rate and final length of annual shoots, according to their architectural position, were related to differences in the total number and diversity of types of sylleptic axillary shoots produced. It is suggested that types and numbers of sylleptic axillary shoots produced are linked with threshold values for both final length and extension rate of the parent shoot. (C) 1999 Annals of Botany Company.