Preformation, neoformation, and shoot structure in Nothofagus dombeyi (Nothofagaceae)

Abstract

Buds in different positions along trunk, main branch, secondary branch, and short branch parent shoots of young Nothofagus dombeyi (Mirb.) Blume trees were dissected, and the number of organs of their rudimentary shoots was counted. Bud contents were compared with the number of organs of sibling shoots developed in positions equivalent to those of the dissected buds. Cataphyll number was relatively constant for all buds. The number of green leaf primordia differentiated in each bud depended both on the position of the bud on the parent shoot and on the size of the parent shoot. Sibling shoots derived distally from large parent shoots had more nodes than the rudimentary shoots of buds in a similar position. Proximal sibling shoots derived from large parent shoots and all sibling shoots derived from small parent shoots are entirely preformed. In N. dombeyi, the size gradient of the sibling shoots derived from a particular parent shoot relates mostly to variation in organ preformation, organ neoformation, and internode extension. The expression of each of these sources of variation is related to the position of the sibling shoot on the parent shoot and on the position of the parent shoot on the tree. Consideration is given to the role of environmental conditions on tree development, in view of the species' morphogenetic gradientsKey words: branching, bud content, sylleptic branching, leaf primordia, Nothofagus, preformation.

Effects of artificial damage on the branching pattern of Nothofagus dombeyi (Nothofagaceae)

“…These proventitious buds do not develop into shoots one year after their inception, unlike more distal axillary buds. Some studies have proposed that these proximal buds might form a "bud bank" able to regenerate the branching system after a major damage to their parent shoot [42,44,51]. According to the present study, this would not be the case when damage involves the distal nodes of N. dombeyi shoots, since none of the treatments applied here affected the position of the most proximal branches on shoots.…”

“…In N. dombeyi trees, like in many other tree species, the branching system consisting of a parent shoot extended in one year and a cohort of offspring shoots extended a year later is characterized by a gradient of increasing offspring shoot size towards the distal end of the parent shoot [42,45,46]. At least for the main branches of young N. dombeyi trees, this gradient seems to be resilient to traumatic factors acting either on the distal portion of a parent shoot before the extension of its offspring shoots (experiments 1 and 2) or on the offspring shoots themselves during their extension (experiment 3).…”

“…(Nothofagaceae) is a relatively abundant evergreen, forest tree species from temperate South America. The basic architecture of this species has been studied in recent years [39,42,43,45]. By mid-summer, at the end of its extension period, each shoot of N. dombeyi bears one axillary bud at all but its most proximal nodes (sylleptic branches may be borne by the most vigorous shoots, usually those of the trunk).…”

“…A terminal bud may also develop but spontaneous apex deaths are very frequent [39]. Each bud of a shoot generates an offspring shoot in the spring following that in which the parent shoot extended; the size of the offspring shoots derived from a common parent shoot usually decreases as the parent shoot's proximal end is approached, as in many other tree species [6,9,39,41,42,45]. Insects belonging to the families Geometridae, Agromicidae, Cerambycidae, Chrysomelidae and Curculionidae may damage buds, leaves and shoots of Nothofagus species [30,34,47].…”

Genotypic Differences in Branching Pattern and Fruiting Habit in Common Walnut (Juglans regia L.)

“…by Seino (2001). Puntieri et al (2000) also reported preformed and neoformed shoots in Nothofagus dombei (Mirb.) Blume.…”