Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

Foliar absorption is a known water acquisition mechanism in many species and ecosystems. Experiments in the field showed that mature black spruce [Picea mariana (Mill.) BSP] can surprisingly sustain periods of summer drought. A possible explanation for this phenomenon is that this species is able to rehydrate via its needles. In this study, we explored if black spruce saplings are able to absorb water via the needles or to increase their water potential and photosynthesis after needle wetting. Forty saplings were used, of which half were excluded from irrigation until water potential of -2.70 MPa. For the first part of the experiment, the saplings were sprayed at night with a colorant solution and water potential was measured the following day. No colorant was absorbed by the saplings and no difference in water potential was found between irrigated and non-irrigated individuals. The experiment was then repeated, spraying saplings with normal water and measuring water potential and photosynthesis. Once again there was no increase in water potential or photosynthesis following the canopy spraying. The results of this study show no evidence of foliar absorption in black spruce saplings. However this does not exclude the occurrence of foliar absorption via passive or active mechanisms in mature trees, which grow under different circumstances.