SHOOT SYSTEMS OF <i>ACER NEGUNDO </i>L. <i>(ACERACEAE) </i>CROWN IN DIFFERENT AGE STAGES
Different levels of the crown structure are distinguished. The diversity of structures formed at each level is shown. Most attention is paid to the second (next to the shoot) level of crown structure, namely two-year shoot systems. Certain types of the two-year shoot systems are specific of <i>A. negundo</i>. They appear in sequence and regularly supersede each other. 8 types of the two-year shoot systems are distinguished; the crown structure at all age stages can be described in terms of these types. The highest diversity of shoot systems is achieved at virginal and young generative age stages. The unification of two-year shoot systems is shown to occur at G2 and G3 age stages. It is found that some types of the shoot systems appear 1—3 times during the crown life, while other types are formed in hundreds.