CONICET | Buscador de Institutos y Recursos Humanos

A good insight into axis differentiation is fundamental to understand plant architecture and disentangle its ecologicalconsequences. The present study was aimed at evaluating the relationship between shoot size/structure and shootgrowth dynamics in Luma apiculata (Myrtaceae), a widely distributed and cultivated but little investigated Andean-Patagonian woody species. We assessed (a) organ preformation in apical buds, (b) shoot growth through repeatedobservations of labeled axes, (c) axillary production, leaf area, stem volume, dry mass in leaves, stem andreproductive structures, and allometric relationships for annual shoots of different sizes. The number of preformedorgans in L. apiculata?s apical buds averages seven nodes and exhibits little variability, in contrast with the highlyvariable growth period (a few weeks up to more than six months) and the size reached by annual shoots. The leafarea/stem volume ratio increased more sharply during shoot extension in shorter than in longer shoots. Stemthickness was proportionally higher than other shoot-size measures in short shoots and long shoots as compared tointermediate-size shoots. Both the presence and the position of branches along shoots varied notably with shoot size.Proportional mass and meristem allocation to fruit production decreased with shoot size. Unlike many otherbroadleaved temperate and temperate-cold tree species so far studied, the size reached by a L. apiculata shoot variesnotably among axes in the same topological position and in the same year, and seems to depend largely on thedevelopment of non-preformed organs. A low dependency of shoot growth on organ preformation may represent anadvantage whenever the duration of conditions favourable for growth exhibits high between-year variation.

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