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Morphology and architecture of
Pinus brutia

From germination to juvenile stage, apical meristems produce leaves, the nature and morphological features of which change along the stem from photosynthetic aciculate leaves to scale leaves. Then photosynthetic assimilation is realised by specialised leaves ("needles") of lateral short axes ("brachyblast" Brachyblast on Brutia pine stem) localised at the axil of scale leaves ("bracts"). In Brutia pine, this transformation is completed in the first year.
The annual growth of this species consists in one or more flushes, the number of which varies from one to six. A strong apical dominance give rise to a highly organised structure around the main stem. All the axes of the architecture are orthotropic and with rhythmic growth and branching. Nevertheless, morphological differences between axes are enough to allow a clear distinction between trunk, branches, twigs,...

Brutia pine seedling

Polycyclism

In young trees, two or three growth units per year may be elongated by the stem. This number reaches six on the main stem for ten to fifteen-year-old trees. Lateral branches can express up to four growth units per year Architectural development. Each growth unit, as already demonstrated in Aleppo pine, shows a particular set of morphological characters according to its position in the annual shoot. Precise characterisation needs a quantitative approach, but up to now it may be stated that the last GU produced in the year is always the smallest. Another feature is the ratio of the leafy part length on the length of the scaly portion. The portion bearing only scale leaves can be so large that some annual shoots seem to produce no needles.

Location of reproductive organs

The first expression of reproductive activity is the production of female cones on distal portions of polycyclic branches. At an older stage, male cones are produced on the distal portion of small monocyclic axes of the lower branches. Female cones may also be produced directly on the trunk of the young tree, though irregularly.

Architectural unit Architectural unit

The about twenty-year-old, five-meter-high young tree expresses the elementary architecture of the species Architectural development. Different axes of the architecture of Brutia pine, may be identified by a special combination of several morphological features that may be grouped in a table and represented by a diagram : this represents the architectural unit of Brutia pine.

Architectural sequence Architectural sequence

Some upper branches of the young tree show a greater development and present the same number of branching order than the trunk. This phenomenon duplicates the initial architecture of the young tree : it is called reiteration Architectural development. During this phase, polycyclism of the main branches is high though no more than four cycles per year are formed ; female cones are present on most of the reiterated complexes. At the same time, male cone production is massive on lower part of the tree. At this step, trunk and main branches bend slightly Architectural development.

On the upper part of bending stems, lateral axes may develop strongly and pile up during development of the crown Architectural development. At this time polycyclism is reduced, the most vigorous axes are bicyclic and bear female cones either on the first growth unit only or on both the first and second growth units. Most of the axes are monocyclic, poorly branched and produce male cones. All the numerous small axes are straight up and lower sagged branches take the appearance of an herbaceous Physiognomy of a branch showing all erected axes and cone-producing-GUs.

The comprehensive architecture of the old tree tends to bend and only some branched systems still grow up. In these complexes, axes are more or less bicyclic and then can be branched ; they allow the extension of tree crown.

Annual shoot with two sucessive female cone

Species Brutia pine - Variability