Shoot neoformation in clones of Fraxinus pennsylvanica in relation to genotype, site and pruning treatments

Abstract

Summary. Four clones of Fraxinus pennsylvanica var. subintegerrima (Vahl) Fern. were planted in replicated trials at two sites in Manitoba (Morden and Winnipeg) to investigate shoot growth and leaf neoformation in relation to genotype, environment and pruning treatment over a 3 year period. Significant differences were found among clones, years and sites for shoot length and numbers of neoformed leaves. Neoformation was highest shortly after transplanting and then declined. An increase in neoformation was evident following cold related winter injury or loss of terminal buds by late spring frosts. Pruning and terminal bud removal treatments both increased neoformed leaf production relative to control trees. The trees were able to quickly re-establish photosynthetic surface area after injury or treatment and neoformed leaf production was an important component in this recovery strategy. The capacity for neoformation also varied in relation to genotype but appeared to be very plastic, 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 shoot length but variation in the relationship suggested that there were differences in intemode length as well. Neoformed leaves were highest in the upper part of the crown indicating that there was differential allocation of resources within the crown.

Shoot preformation in clones of Fraxinus pennsylvanica in relation to site and year of bud formation

“…In addition, the trees were less exposed to freezing injury at this site and were clearly more vigorous (Davidson and Remphrey 1993). Remphrey (1989) concluded that environmental influences were important in bud development in mature F. pennsylvanica based on year to year variation.…”

A review of site factors affecting the early growth of ash (Fraxinus excelsior L.)

“…Gill (1971) reported one of the first studies on white ash, although it was limited to comparing only 15 terminal buds of opposite branches. More detailed work by Remphrey and Davidson (1994) and Davidson and Remphrey (1994) has shown that green ash has the capacity for both preformation and neoformation; the latter is where shoots are not entirely preformed in the resting bud and a proportion of the leaves is formed during the growth season. This was the first report of neoformation in Fraxinus and was shown to be an important part of the plant's recovery strategy after pruning or the loss of terminal buds in late spring frosts.…”

Neoformed growth responses to dormant pruning in mature and immature pistachio trees grown on different rootstocks

“…This likely led to greater structural complexity, and may have increased intrashoot competition (Hackett, 1985), resulting in the general decline in neoformed growth as time from pruning elapsed. Davidson and Remphrey (1994) found a similar decline in neoformed growth as Fraxinus pennsylvanica trees matured, and their architectural complexity increased.…”

“…Davidson and Remphrey (1994) found that pruning, as well as the removal of buds, and thus potentially competing shoots, increased neoformation in Fraxinus pennsylvanica Marsh. However, their study was limited to young trees (4 -5 years-old).…”