Diurnal and seasonal variations in gas exchange and water relations of lowland and upland black spruce ecotypes

摘要

Gas exchange and water relations were measured on seedlings from two pairs of upland and lowland black spruce (Picea mariana(Mill.) BSP) populations. The seedlings were planted under natural atmospheric conditions in exterior sand beds. Measurements were carried out on eight separate days during the summer of 1992. Diurnal and seasonal responses of gas exchange and water relations parameters to natural changes in environmental factors were analyzed for possible ecotypic differences. Differences were found among the four populations and within one of the two uplandndash;lowland pairs. However, no differences could be linked significantly to an uplandndash;lowland ecotypic differentiation. The physiological responses are discussed with respect to diurnal and seasonal changes in environmental factors and to similarities with results from an earlier experiment involving mature trees from the same four populations.Key words:Picea mariana, water stress, net photosynthesis, stomatal conductance.