Revista Chilena de Historia Natural 79 (4): 489-504, 2006
RESEARCH ARTICLE
Seasonal changes in the photosynthetic performance of two evergreen Nothofagus
species in south central Chile
The evergreen Nothofagus dombeyi and Nothofagus nitida are
important members of the temperate Chilean rainforest. They seldom grow together in nature. Nothofagus nitida is more
susceptible to excess light and drought than N. dombeyi. We postulate that the different properties of the photosynthetic
apparatus under common garden conditions of these species could explain their contrasting habitat preferences. The two species
growing in a common garden in south central Chile were studied. The optimal photochemical efficiency (Fv/Fm) of both species
remained within normal values (≈ 0.8) with the exception of a decrease in N. dombeyi at midday in summer, suggesting
reversible reduction in photochemical efficiency of photosystem II (PSII). During summer the effective photochemical efficiency
(F<sub>PSII</sub>), photochemical quenching (qP), photosynthesis
(A<sub>max</sub>), stomatal conductance (gs) and transpiration rates (E) in N. dombeyi were higher than in
N. nitida. The highest increments in photoprotective pigments (zeaxanthin + antheraxanthin and lutein) contents between
predawn and midday were obtained in summer in N. dombeyi. In N. nitida a nocturnal retention of dissipative
pigments, without a decrease in Fv/Fm, was found in winter. The results suggest that N. dombeyi showed a better
photosynthetic performance than N. nitida under high light, high temperature, and drier conditions. These data support are
consistent with the pioneer character of N. dombeyi and the semitolerant shade properties and more restricted distribution
of N. nitida. These photosynthetic characteristics, along with their freezing and flooding resistance differences, may result
from their habitat separation.
Key words:
chlorophyll
fluorescence, photosynthesis, Nothofagus dombeyi, Nothofagus nitida, xanthophyll cycle
