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Morphology and architecture of
Cedrus atlantica Manetti ex Carrière

One-year-old seedling

At spring time, the seed opens and a hypocotyl bearing a rosette of ten cotyledons around a meristem is edified. During the season of growth, this axis extend and bear, above cotyledons, a succession of needles with alternate spiral arrangement (the number of foliar spires varies to 3 to 9 according to individuals) which may remain 2 to 3 years. In natural regeneration, the extension of the stem is short whereas, in nursery, it may to reach twenty centimetres (one-year-old seedlings in natural regeneration Regeneration and in nursery Nursery). In this case, the main stem bears a succession of branches with immediate development. At the end of the growth season, two to four big buds are presents at the top of the main stem and will give rise to one pseudowhorl of dominant branches at the following spring.

Atlantica cedar seedling

Young tree and structure of annual shoots

Growth in Cedar is rhythmic and all axes are built up of by succession of annual shoots. At the spring time, the current annuals shoots are often slanted and generally straighten up from the July beginning. The shoot growth rate decreases progressively from the main stem, which grows with a vertical direction, to the branches and the branchlets, which grow in a horizontal direction (mean cumulative length of currently-elongating shoots according to axis category over a growing season Mean cumulative length of currently-elongating shoots).

In natural regeneration, the first annual shoots of the main stem have a small size. The following years, the apical meristem of the main stem normally forms successive annual shoots of increasing number of leaves and increased length Four-year-old tree growing in forest. Vigorous annual shoots may develop lateral axes in the same year that their extension. These lateral axes correspond to a mixture of short and long shoots. In this case, branching of current year annual shoots is immediate and the most vigorous lateral shoots have a median position on the bearing shoot. The following year, bearing shoots develop shoots from dormant buds which are located in apical position on the bearing shoot and their lateral axes continue to grow. Like this, lateral axes show an acrotonic gradient of decreasing vigour from the top to the base of the bearing shoot Structure of one- and two-year-old annual shoots. The branches with immediate development are characterised by the absence of scaly leaves associated with the absence of a protecting resting stage at their base.

At the level of the whole tree, the nature and the number of axillary productions borne on the one-year-old annual shoot vary according to this size Structure of annual shoots in relation to their decreasing size. Scale is 1 cm..

Young tree and architectural unit Architectural unit

At this development stage, the tree presents a pyramidal form. This architecture show a very precise organisation concerning the nature and relative position of morphological discernible categories of axes. In young individuals of Cedrus atlantica, five different categories of axes may be identifiable. The main stem is a vertical monopodial axis with indefinite and rhythmic growth. Its branching pattern is rhythmic. The branches may have an differed (proleptic) or immediate (sylleptic) development according their position on the annual shoots. The branches are arranged in pseudowhorls. They have a horizontal to slanted direction of growth. Branches have a long term definite and rhythmic growth and follow a monopodial and rhythmic branching pattern. Branchlets are regularly arranged on branches more or less in a single plane. They have a long term determinate growth. Their direction of growth is horizontal. As branches, branching pattern of branchlets is a differed or immediate development. Twigs have a rhythmic branching with differed development. Twigs have a medium term determinate growth. Brachyblasts have a short term determinate growth, remain unbranched. They bear terminal male or female cones.

These features represent a simple hierarchical morphological and functional specific elementary architecture or "architectural unit" here summarised.

Young tree

Adulte tree

After the expression of its architectural unit, the tree will continue to develop its trunk and to remain regularly branched 12-year-old tree growing in open field. Oldest branches increase their volume by a process partially reiteration of the architectural unit. At the top of the branches, a sub-apical bud of the annual shoot develops to a vigorous shoot. This phenomenon give rise to fork formation. Thus, the repeating of this process allows the development of branches. During following years, this phenomenon of fork formation progressively invades the branches.

The sexuality appears at this development stage of the tree. The female or male flowering are terminal on brachyblasts which are constituted to 3 or 4 vegetative short shoots SexualitySexuality.

Female flowering affect brachyblasts borne by the most vigorous axes: the main stem, the branches and reitered branchlets. The first flowering is generally located on the upper part of the tree Adult tree and first female flowering. During successive flowering, the floriferous zone spreads toward the tree periphery and progressively invades its crown Flowering. Male flowering is located on the brachyblasts corresponding to highest orders of branching. Male flowering is distributed at the periphery of female floriferous zone Flowering.

As the tree continues its development, new branches located in the upper part of trees develop in accordance with the architectural unit of these species. In the lower part of trees, the branches form more and more short annual shoots and finally die.

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.

One-year-old seedling

As the tree becomes older, the growth of the main stem progressively decreases. A decreasing of the ability to straighten up of annual shoots of the main stem. The direction of growth becomes oblique to horizontal. The main stem progressively takes the development pattern of a branch. This phenomenon involves the edification of "tabular form" crown. At this development stage, the tree reached its maximal height and its tabular crown expands.

Old tree

Architectural sequence Architectural sequence

Species Atlantica cedar - Variability