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

Abstract

Summary. Shoot preformation was investigated in buds of four clones of Fraxinus pennsylvanica var. subintegerrima (Vahl) Fern. at two sites in Manitoba in the second (1988) and third (1989) growing seasons after grafting. More preformed primordia were produced in terminal buds in 1989 compared to 1988 at each site. Both terminal and lateral buds at Morden contained significantly more primordia than those at Winnipeg. The numbers of preformed primordia were significantly different among clones. Clone 3 produced the most and clone 1 the fewest primordia in terminal buds. Despite quantitative variation, the pattern was similar among clones for terminal buds at each site and in each year. A similar pattern was evident for lateral buds at the Winnipeg site in 1989 but at Morden, clones 4 and 1 had the largest number of preformed primordia. Data from 1989 revealed that numbers of primordia were correlated with bud dimensions, parent shoot length, diameter and number of leaves, and location of the bud on the parent. Shoot dry weight was also related to these variables and revealed a non-linear increase in dry weight with shoot length. Multiple regression, with parent shoot length and location of buds along the parent axis as independent variables provided a reliable indicator of preformation in the crown. Although there is a genotypic component to preformation, variation between sites, years and crown locations suggests plasticity in bud development.

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

“…However, part of this variation may be explained by the results of a previous investigation which revealed genotypic differences in preformation (Remphrey and Davidson, 1994). The result of these differences is that shorter shoots in some clones exhibit more neoformation than similar sized shoots in other clones (compare clones 4 and 3 in Fig.…”

“…2, 3). The number of preformed leaves also increased but at a lower rate (Remphrey and Davidson, 1994). The difference between total leaves and the preformed complement represents an estimate of neoformation.…”

“…subintergerrima (Vahl) Fern. revealed differences in preformation among clones, sites and years (Remphrey and Davidson, 1994). Neoformation of leaves in F. pennsylvanica has not been reported but initial observation of nursery plants and young saplings indicated that neoformation could be occurring (Davidson, personal observation).…”

“…Preformed leaf estimates were obtained from specific regression equations based on parent shoot length and the location of the bud on the parent shoot for each clone and site (Remphrey and Davidson, 1994). All data were analysed with a VAX 3400 mini-computer with SAS (Ver 6.0) statistical programs (SAS 1991).…”

Summer-drought constrains the phenology and growth of two coexisting Mediterranean oaks with contrasting leaf habit: implications for their persistence and reproduction

“…In species with preformed growth such as oaks (Collin et al 1996;Fontaine et al 1999), larger buds produce longer shoots with more leaves (Isik 1990;Hanover 1963;MacDonald et al 1984;Remphrey and Powell 1984;Remphrey and Davidson 1994;Thorp et al 1994). On the other hand, small buds will produce smaller and less numerous shoots on the following year, because many small buds tend either to abort or to produce short modules.…”