ABSTRACT
Atmospheric and climate change will expose tropical forests to
conditions they have not experienced in millions of years. To better
understand the consequences of this change we studied photosynthetic
acclimation of the neotropical tree species Tabebuia rosea to
combined 4°C warming and twice-ambient (800 ppm) CO2. We
measured temperature responses of the maximum rates of
ribulose 1,5-bisphosphate
carboxylation (VCMax), photosynthetic electron transport
(JMax), net photosynthesis (PNet), and
stomatal conductance (gs), and fitted the data using a
probabilistic Bayesian approach. To evaluate short-term acclimation
plants were then switched between treatment and control conditions and
re-measured after 1–2 weeks. Consistent with acclimation, the optimum
temperatures (TOpt) for VCMax,
JMax and PNet were 1–5°C higher in
treatment than in control plants, while photosynthetic capacity
(VCMax, JMax, and PNetat TOpt) was 8–25% lower. Likewise, moving control
plants to treatment conditions moderately increased temperature optima
and decreased photosynthetic capacity. Stomatal density and sensitivity
to leaf-to-air vapor pressure deficit were not affected by growth
conditions, and treatment plants did not exhibit stronger stomatal
limitations. Collectively, these results illustrate the strong
photosynthetic plasticity of this tropical tree species as even
fully-developed leaves of saplings transferred to extreme conditions
partially acclimated.
Keywords : Acclimation, Climate change, JMax,
Global warming, Photosynthetic temperature response, Stomatal
conductance, Tropical forest, VCMax, VPD