MORPHOLOGY OF SILVER FIR (ABIES-ALBA MILL ) .1. CONCEPT AND ELEMENTS OF TREE ARCHITECTURE

The concept of ecological morphology of woody plants is based both on the exact description of single structural elements and architecture. These must be described under optimal environmental conditions (ideal phenotype) as well as on variations in the ideal phenotype induced by changes in the environment (modifications). The latter result in degen eration and subsequently deviation from the ideal type. Through regene ration and reiteration trees can grow back to a form approaching the i deal type. A whole plant approach is followed in which morphology depe ndent on ontogeny and the environment (genetic-environment interaction ) is presented. Morphological and anatomical investigations on the tru nk, crown and needles were carried out on 100-130 year old fir trees f rom Yugoslavia (Pokljuka) and the Black Forest as well as on young fir s. The most important results are as follows: In fir the terminal bud has a simple anatomy (bud category 1) with a developmental cycle of a single period. In lateral buds, regularly sprouting buds and suppresse d buds (proventitious buds), can be distinguished both morphologically and phenologically. For spruce the morphogenetic cycle of the regular bud can be divided into three phases; the growth phase I (bud scale f ormation), growth phase II (formation of needle primordia) and the dor mant phase (overwintering of the buds). The shoot and needle developme nt from regularly developed buds can be distinguished on the basis of the phyllochrone (dormancy period) between the premature (proleptic), the normal (regular) and retarded (proventitious) differentiation. In young fir trees the regular shoot development predominates, whereas in older trees the proventitious shoot development is most common. The r egular annual shoot of fir can be divided into a stunted and elongated shoot part. The elongated part can be subdivided into a distal regula rly sprouting bud area and a proximal area of suppressed buds. The bra nch development of the annual shoots is acrotonous, the growth is mono podial (distally oriented shoot development). The subsequent shoot dev elopment results from proventitious buds on the stems as well as from buds in the primary crown. Due to this the twigs and branches can be p ut back on the dormant axes (proximally oriented shoot development). T he proventitious branches in the primary crown are formed from provent itious buds mainly in first and second order axes and epitonously. Usi ng the proventitious branches on the trunk firs can develop a complete ly new and ''basally transferable'' (towards the roots) crown (provent itious secondary crown). This can be formed as light-adapted or as sha de-adapted crown. The proventitious shoots serve as substitutes for in sufficient crown parts, the regeneration of the crown, the adaptation of the crown to develop an optimal form for the given environmental co nditions and also to exploit the light in favourable growth phases. Th e flowers and inflorescences are formed as preformed structural elemen ts. The male flowers are developed medially and hypotonously on the sh oots of higher order. The female inflorescences are developed medially and epitonously on axes of first and second order. In young firs the angle at which the axes of first order grow is on average 67 degrees. The needle form and in particular the needle tip, changes in dependenc e upon the shoot order (topophylly). The anatomy of the abscission zon e of fir needles is described. The fir needle sits directly on the cor k layer, which is a single period active bark periderm of the shoot ax is in this area. In contrast to spruce, needle fall does not follow th e rhexolytic shrinking mechanism.