Partial shoot reiteration in Wollemia nobilis (Araucariaceae) does not arise from ‘axillary meristems’

Abstract

Axillary meristems in Wollemia characterize the leaf axils of trunk axes so that the origin of reiterated shoots is clear. Plagiotropic axes seemingly lack axillary meristems but still produce axillary branches by distinctive developmental processes. These observations demonstrate limited understanding of branch initiation in trees generally.

Elusive but not hypothetical: axillary meristems in Wollemia nobilis

“…Interestingly, in an earlier paper, Tomlinson and Murch (2009) did mention that Burrows (1999) had found axillary meristems in plagiotropic branches of Wollemia. Tomlinson and Huggett (2011) is not the first paper to report a failure to locate araucarian axillary meristems. Holthusen (1940) did not find meristems or buds in the apparently blank leaf axils of 22 species of conifers in 11 genera, including four species of Araucariaceae.…”

“…As noted, Tomlinson and Huggett (2011) did not refer to published information (both text and photomicrographs) that demonstrate the presence of axillary meristems in branch leaf axils of Wollemia nobilis (Burrows, 1999). Tomlinson and Huggett state that the suggestion [from information in Burrows (1999) and Burrows et al (2003)] that all leaf axils in the Araucariaceae were potential sites for future bud development 'was made only with reference to orthotropic shoots'.…”

“…I have two concerns with this statement. Firstly, that Tomlinson and Huggett (2011) do not refer to previously published information that indicates that axillary meristems are present in Wollemia branch leaf axils, and secondly, their anatomical methods were probably not optimal for locating and examining these minute structures.…”

“…res.). Tomlinson and Huggett (2011) have recently investigated the formation of these reiterative branches.…”

Sectional model of non-free tree growth

“…Комбинированная модель, учитывающая эти особенности, хорошо согласуется с натурными данными и другими публикациями; модель же только регулярных ветвей показывает наличие ветвей только 1-го порядка, а при дополнении ее субмоделью начального торможения роста имеются ветви всех четырех порядков. Необходимость учета межмутовочных ветвей в этой модели [Галицкий, 2012] вместе с известными особенностями транспорта ассимилятов в деревьях [Курсанов, 1976; Галицкий, 2009] и результатами экспериментов [Tomlinson, Haggett, 2011] по декапитации ветвей Wollemia nobilis (Araucariaceae) указывают, что причиной появления межмутовочных ветвей ели может быть необходимость компенсации перепадов давления ассимилятов во флоэмной сети, связанной с нестабильностью светового режима.…”