Photosynthetic plasticity of a tropical tree species, Tabebuia rosea, in response to elevated temperature and [CO₂]

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 PNet at 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 vapour 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.

Thermal optimum of photosynthesis is controlled by stomatal conductance and does not acclimate across an urban thermal gradient in six subtropical tree species

“…Each point represents an individual tree, solid lines are significant relationships (p < 0.05), and dotted lines are nonsignificant relationships. Hall et al, 2013;Kumarathunge et al, 2019;Yamaguchi et al, 2016), even in tropical tree species (Slot et al, 2021). Contrary to our results, previous studies have also shown decreasing A opt with increasing T optA due to performance tradeoffs in the underlying processes (Berry & Bjorkman, 1980;Dusenge, Wittemann, et al, 2021;Slot et al, 2021;, although in a meta-analysis Way and Yamori (2014) demonstrated that acclimation of T optA does not correspond to a consistent response in A opt across 103 species, possibly related to a cross-biome pattern of reduced ability to acclimate towards the (Crous, 2019;Crous et al, 2018).…”

“…In addition, the activation state of Rubisco in most trees across all the study species did not significantly limit A net , and individuals in which Rubisco limitation was observed at high temperatures did not have significantly reduced A opt . This result is similar to some observations on the tropical tree Tabebuia rosea (Slot et al, 2021) and various herbaceous species (Sage et al, 2008), but contrary to other results showing significant high-temperature…”

“…V cmax at T optA (J maxTopt :V cmaxTopt ). Additionally, we calculated the entropy term (ΔS) of V cmax and J max according to Medlyn et al (2002) and Slot et al (2021) as:…”

“…These models depend on an accurate understanding of the temperature responses of the component processes of photosynthesis within and among species and across space and time (Kumarathunge et al, 2019; Lin et al, 2012). Currently, models are limited by a poor representation of the potential acclimation of the underlying components of net photosynthesis ( A net ) to increased temperature, especially in tropical plants (Lombardozzi et al, 2015; Mercado et al, 2018; Slot et al, 2021; N. G. Smith & Dukes, 2013), due to a sparsity of empirical data characterizing temperature responses (Slot & Winter, 2017a). Earth's atmosphere has already warmed by ≥1°C since 1850–1900 and is predicted to warm by an additional 1.0–5.7°C this century, depending on emissions scenarios (IPCC, 2021).…”

Scaling plant responses to high temperature from cell to ecosystem

“…Perez et al (2021) found that high heat tolerance of PSII was associated with species that were thermal generalists, thus providing a proxy for evaluating the thermal niche of plants, while Slot, Cala, et al (2021) showed that PSII heat tolerance varies in a predictable way with site temperature and elevation. The ability to acclimate CO 2 uptake rates to higher temperatures is often related to shifts in the thermal sensitivity and capacity of photosynthetic processes, and can occur quite quickly (Slot, Rifai, & Winter, 2021).…”