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Variability of initial growth, water-use efficiency and carbon isotope discrimination in seedlings of Faidherbia albida (Del.) A. Chev., a multipurpose tree of semi-arid Africa. Provenance and drought effects

Roupsard O., Joly H., Dreyer E.. 1998. Annales des Sciences Forestières, 55 : p. 329-348.

DOI: 10.1051/forest:19980305

The panafrican provenances of Faidherbia albida display contrasting growth and survival rates in semi-arid zones of western Africa, when they are compared in multi-local field trials. In order to identify some potential causes for such differences, we recorded the genetic variability of ecophysiological traits (including water-use efficiency, W, and carbon isotope discrimination, A) in seven provenances from contrasting habitats of western and south-eastern Africa. Provenance and drought effects were tested on potted seedlings in a greenhouse. After 6 months, the total dry mass of the well-irrigated seedlings ranged from 31 to 86 g, and the total water-use from 8 to 18 kg. Both initial growth and water consumption were strongly correlated with leaf area. We displayed a significant inter-provenance variability, and exhibited the highest values in the south-east African provenances, which were the most vigourous, but also presented the poorest survival rates in field trials. It was negatively con-elated with the leaf-to-total dry mass ratio, LMR, and to A. The mild drought significantly reduced gas-exchange rates, leaf area, growth, water-use, specific leaf area, and A in all provenances. It also increased the intrinsic water-use efficiency, A/g, and the root-to-total dry mass ratio, but did not affect W or LMR. No provenance x drought interaction was found in any variable. The initial rate of leaf area establishment probably plays a major role in explaining the contrasting water-use strategies of the provenances.

Mots-clés : stade juvénile des plantes; exigence des plantes; relation plante eau; potentiel hydrique; facteur du milieu; stress dû à la sécheresse; variation génétique; variation saisonnière; phénologie; résistance à la sécheresse; provenance; croissance

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