CONICET | Buscador de Institutos y Recursos Humanos

The growth dynamics of annual shoots of shrubby Nothofagus antarctica plants growing in northern Patagonia was studied. The pattern of extension of shoots derived from the three most distal buds of 100 bearing shoots of comparable size was registered through weakly measures and observations of shoots extending during the 1996-97 growth season. These buds were numbered since the apex, being the most distal the number one, the next the number two and the next the number trhee. The date of shoot extension initiation was less variable than the date of shoot extension cessation. Extension curves had an asymmetrically sigmoideal outline. Most extension took place between 12 September 1996 and 30 January 1997. Shoot extension was uninterrupted. The extension peak was registered on 19 December 1996, and was followed by a sharp decrease in extension rate. All measured shoots had definite growth: their apical meristem died by the end of the growth season. In general terms, the length, the leaf number and the extension duration of shoots decreased from the apex to the another position analised. However, cases in which a maximun growth took place for not most distally-placed shoot of the same bearing shoot, were recorded. Fertile and sterile shoots were similar with respect to extension rate and length. The presence of flowers is similar in the three position of shoots analized. Shoot extension is affected by maximum and minimum daily tempeartures but not by the amount of precipitations during the extension period. Bud size immediately before budbreak were approximately similar both in length and in width trought the bearing shoot. Bud size was not a good predictor of the final size of the shoot derived from that bud. The length of the produced shoots was related to the length of the bearing shoots.

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