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1. Global climate and nutrient controls of photosynthetic capacity

   https://doi.org/10.1038/s42003-021-01985-7  

   Peng, Yunke ; Bloomfield, Keith J. ; Cernusak, Lucas A. ; Domingues, Tomas F. ; Colin Prentice, I. ( December 2021 , Communications Biology)

   null (Ed.)

   Abstract There is huge uncertainty about how global exchanges of carbon between the atmosphere and land will respond to continuing environmental change. A better representation of photosynthetic capacity is required for Earth System models to simulate carbon assimilation reliably. Here we use a global leaf-trait dataset to test whether photosynthetic capacity is quantitatively predictable from climate, based on optimality principles; and to explore how this prediction is modified by soil properties, including indices of nitrogen and phosphorus availability, measured in situ. The maximum rate of carboxylation standardized to 25 °C ( V cmax25 ) was found to be proportional to growing-season irradiance, and to increase—as predicted—towards both colder and drier climates. Individual species’ departures from predicted V cmax25 covaried with area-based leaf nitrogen ( N area ) but community-mean V cmax25 was unrelated to N area , which in turn was unrelated to the soil C:N ratio. In contrast, leaves with low area-based phosphorus ( P area ) had low V cmax25 (both between and within communities), and P area increased with total soil P. These findings do not support the assumption, adopted in some ecosystem and Earth System models, that leaf-level photosynthetic capacity depends on soil N supply. They do, however, support a previously-noted relationship between photosynthesis and soil P supply. 

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2. Sensitivity analysis and estimation using a hierarchical Bayesian method for the parameters of the FvCB biochemical photosynthetic model

   https://doi.org/10.1007/s11120-019-00684-z  

   Han, Tuo ; Zhu, Gaofeng ; Ma, Jinzhu ; Wang, Shangtao ; Zhang, Kun ; Liu, Xiaowen ; Ma, Ting ; Shang, Shasha ; Huang, Chunlin ( October 2019 , Photosynthesis research)

   Photosynthesis is a major process included in land surface models. Accurately estimating the parameters of the photosynthetic sub-models can greatly improve the ability of these models to accurately simulate the carbon cycle of terrestrial ecosystems. Here, we used a hierarchical Bayesian approach to fit the Farquhar–von Caemmerer–Berry model, which is based on the biochemistry of photosynthesis using 236 curves for the relationship between net CO2 assimilation and changes in the intercellular CO2 concentration. An advantage of the hierarchical Bayesian algorithm is that parameters can be estimated at multiple levels (plant, species, plant functional type, and population level) simultaneously. The parameters of the hierarchical strategy were based on the results of a sensitivity analysis. The Michaelis–Menten constant (Kc25), enthalpies of activation (EJ and EV), and two optical parameters (θ and α) demonstrated considerable variation at different levels, which suggests that this variation cannot be ignored. The maximum electron transport rate (Jmax25), maximum rate of Rubisco activity (Vcmax25), and dark respiration in the light (Rd25) were higher for broad-leaved plants than for needle-leaved plants. Comparison of the model’s simulated outputs with observed data showed strong and significant positive correlations, particularly when the model was parameterized at the plant level. In summary, our study is the first effort to combine sensitivity analysis and hierarchical Bayesian parameter estimation. The resulting realistic parameter distributions for the four levels provide a reference for current and future land surface models. Furthermore, the observed variation in the parameters will require attention when using photosynthetic parameters in future models. 

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3. Soil nitrogen fertilization reduces relative leaf nitrogen allocation to photosynthesis

   https://doi.org/10.1093/jxb/erad195  

   Waring, Elizabeth F. ; Perkowski, Evan A. ; Smith, Nicholas G. ; Rogers, ed., Alistair ( May 2023 , Journal of Experimental Botany)

   The connection between soil nitrogen availability, leaf nitrogen, and photosynthetic capacity is not perfectly understood. Because these three components tend to be positively related over large spatial scales, some posit that soil nitrogen positively drives leaf nitrogen, which positively drives photosynthetic capacity. Alternatively, others posit that photosynthetic capacity is primarily driven by above-ground conditions. Here, we examined the physiological responses of a non-nitrogen-fixing plant (Gossypium hirsutum) and a nitrogen-fixing plant (Glycine max) in a fully factorial combination of light by soil nitrogen availability to help reconcile these competing hypotheses. Soil nitrogen stimulated leaf nitrogen in both species, but the relative proportion of leaf nitrogen used for photosynthetic processes was reduced under elevated soil nitrogen in all light availability treatments due to greater increases in leaf nitrogen content than chlorophyll and leaf biochemical process rates. Leaf nitrogen content and biochemical process rates in G. hirsutum were more responsive to changes in soil nitrogen than those in G. max, probably due to strong G. max investments in root nodulation under low soil nitrogen. Nonetheless, whole-plant growth was significantly enhanced by increased soil nitrogen in both species. Light availability consistently increased relative leaf nitrogen allocation to leaf photosynthesis and whole-plant growth, a pattern that was similar between species. These results suggest that the leaf nitrogen–photosynthesis relationship varies under different soil nitrogen levels and that these species preferentially allocated more nitrogen to plant growth and non-photosynthetic leaf processes, rather than photosynthesis, as soil nitrogen increased.

    

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4. Global patterns and drivers of leaf photosynthetic capacity: The relative importance of environmental factors and evolutionary history

   https://doi.org/10.1111/geb.13660  

   Yan, Zhengbing ; Sardans, Jordi ; Peñuelas, Josep ; Detto, Matteo ; Smith, Nicholas G. ; Wang, Han ; Guo, Lulu ; Hughes, Alice C. ; Guo, Zhengfei ; Lee, Calvin K. ; et al ( May 2023 , Global Ecology and Biogeography)

   Abstract Aim Understanding the considerable variability and drivers of global leaf photosynthetic capacity [indicated by the maximum carboxylation rate standardized to 25°C ( V c,max25 )] is an essential step for accurate modelling of terrestrial plant photosynthesis and carbon uptake under climate change. Although current environmental conditions have often been connected with empirical and theoretical models to explain global V c,max25 variability through acclimatization and adaptation, long‐term evolutionary history has largely been neglected, but might also explicitly play a role in shaping the V c,max25 variability. Location Global. Time period Contemporary. Major taxa studied Terrestrial plants. Methods We compiled a geographically comprehensive global dataset of V c,max25 for C 3 plants ( n  = 6917 observations from 2157 species and 425 sites covering all major biomes world‐wide), explored the biogeographical and phylogenetic patterns of V c,max25 , and quantified the relative importance of current environmental factors and evolutionary history in driving global V c,max25 variability. Results We found that V c,max25 differed across different biomes, with higher mean values in relatively drier regions, and across different life‐forms, with higher mean values in non‐woody relative to woody plants and in legumes relative to non‐leguminous plants. The values of V c,max25 displayed a significant phylogenetic signal and diverged in a contrasting manner across phylogenetic groups, with a significant trend along the evolutionary axis towards a higher V c,max25 in more modern clades. A Bayesian phylogenetic linear mixed model revealed that evolutionary history (indicated by phylogeny and species) explained nearly 3‐fold more of the variation in global V c,max25 than present‐day environment (53 vs. 18%). Main conclusions These findings contribute to a comprehensive assessment of the patterns and drivers of global V c,max25 variability, highlighting the importance of evolutionary history in driving global V c,max25 variability, hence terrestrial plant photosynthesis. 

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5. Climate warming alters photosynthetic responses to elevated CO 2 in prairie plants

   https://doi.org/10.1002/ajb2.1532  

   Sage, Emma ; Heisler‐White, Jana ; Morgan, Jack ; Pendall, Elise ; Williams, David G. ( September 2020 , American Journal of Botany)

   The impact of elevated CO₂concentration ([CO₂]) and climate warming on plant productivity in dryland ecosystems is influenced strongly by soil moisture availability. We predicted that the influence of warming on the stimulation of photosynthesis by elevated [CO₂] in prairie plants would operate primarily through direct and indirect effects on soil water.

   We measured light‐saturated photosynthesis (A_net), stomatal conductance (g_s), maximum Rubisco carboxylation rate (V_cmax), maximum electron transport capacity (J_max) and related variables in four C₃plant species in the Prairie Heating and CO₂Enrichment (PHACE) experiment in southeastern Wyoming. Measurements were conducted over two growing seasons that differed in the amount of precipitation and soil moisture content.

   A_netin the C₃subshrubArtemisia frigidaand the C₃forbSphaeralcea coccineawas stimulated by elevated [CO₂] under ambient and warmed temperature treatments. Warming by itself reducedA_netin all species during the dry year, but stimulated photosynthesis inS. coccineain the wet year. In contrast,A_netin the C₃grassPascopyrum smithiiwas not stimulated by elevated [CO₂] or warming under wet or dry conditions. Photosynthetic downregulation under elevated [CO₂] in this species countered the potential stimulatory effect under improved water relations. Warming also reduced the magnitude of CO₂‐induced down‐regulation in this grass, possibly by sustaining high levels of carbon utilization.

   Direct and indirect effects of elevated [CO₂] and warming on soil water was an overriding factor influencing patterns ofA_netin this semi‐arid temperate grassland, emphasizing the important role of water relations in driving grassland responses to global change.

    

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