SHOOT NEOFORMATION IN CLONES OF FRAXINUS-PENNSYLVANICA IN RELATION TOGENOTYPE, SITE AND PRUNING TREATMENTS

Four clones of Fraxinus pennsylvanica var. subintegerrima (Vahl) Fern. were planted in replicated trials at two sites in Manitoba (Morden an d Winnipeg) to investigate shoot growth and leaf neoformation in relat ion to genotype, environment and pruning treatment over a 3 year perio d. Significant differences were found among clones, years and sites fo r shoot length and numbers of neoformed leaves. Neoformation was highe st shortly after transplanting and then declined. An increase in neofo rmation was evident following cold related winter injury or loss of te rminal buds by late spring frosts. Pruning and terminal bud removal tr eatments both increased neoformed leaf production relative to control trees. The trees were able to quickly re-establish photosynthetic surf ace area after injury or treatment and neoformed leaf production was a n important component in this recovery strategy. The capacity for neof ormation also varied in relation to genotype but appeared to be very p lastic, being affected by a wide variety of factors. In addition, the rate or pattern of change in amounts of neoformed leaves over time and locations was variable. Numbers of neoformed leaves increased with sh oot length but variation in the relationship suggested that there were differences in intermode length as well. Neoformed leaves were highes t in the upper part of the crown indicating that there was differentia l allocation of resources within the crown.