Maximum Carboxylation Rate Estimation With Chlorophyll Content as a Proxy of Rubisco Content

Abstract

The maximum carboxylation rate (Vcmax) is a key parameter in determining the plant photosynthesis rate per unit leaf area. However, most terrestrial biosphere models currently treat Vcmax as constants changing only with plant functional types, leading to large uncertainties in modeled carbon fluxes. Vcmax is tightly linked with Ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco). Here we investigated the relationship between leaf chlorophyll and Rubisco (Chl‐Rub) contents within a winter wheat paddock. With chlorophyll as a proxy of Rubisco, a semimechanistic model was developed to model Vcmax25 (Vcmax normalized to 25°C). The Chl‐Rub relationship was validated using measurements in a temperate mixed deciduous forest in Canada. The results showed that Rubisco was strongly correlated with chlorophyll (R2 = 0.96, p < 0.001) for winter wheat since the absorption of light energy by chlorophyll and the amount of CO2 catalyzed by Rubisco are tightly coupled. Incorporating the Chl‐Rub relationship into the semimechanistic model, the root mean square error of modeled Vcmax25 was the lowest among all estimation models. The slopes of Chl‐Rub relations were almost consistent in the winter wheat and temperate forest, demonstrating the potential for using leaf chlorophyll content as a proxy of leaf Rubisco in modeling Vcmax25 at large spatial scales. We anticipate that improving Vcmax25 estimates over time and space will reduce uncertainties in global carbon budgets simulated by terrestrial biosphere models.

Limited thermal acclimation of photosynthesis in tropical montane tree species

“…This is because enzymatic reactions are faster at high temperatures; therefore, warm‐grown plants can achieve optimal net CO 2 assimilation rates with a relatively lower photosynthetic enzyme content (Smith & Keenan, 2020; Yamori et al, 2014). Since both Rubisco carboxylation and electron transport rates, and the contents of the enzymes that regulate each process (Rubisco and chlorophyll pigments) are co‐regulated (Lu et al, 2020; Maire et al, 2012; Wullschleger, 1993), then warm acclimated plants should consequently reduce both V cmax and J max . Since respiration is involved in providing energy for protein turn over, which is the largest factor that explains variation in leaf R d , then thermal acclimation of respiration should closely follow that of photosynthetic capacity (Wang et al, 2020).…”

A test of rapid leaf photosynthesis-intercellular CO2 concentration response (RACiR) technique for evergreens and herbs

“…Our study showed that V cmax andJ max calculated by RACiR curves under multiple [CO 2 ] gradients were not significantly different from TACiR curves, indicating that the RACiR technique could be applied to herbs as well as evergreen species (Pilon et al 2018, Lu et al 2020, McKenzie-Gopsill et al 2020, Vincent et al 2020, Liu and van Iersel 2021 and thus is likely to be generalizable among different plant life forms.…”

Plant Evolution History Overwhelms Current Environment Gradients in Affecting Leaf Chlorophyll Across the Tibetan Plateau

“…As opposed to most previous studies conducted at the local scale (Croft et al, 2015(Croft et al, , 2017Lu et al, 2020), this study presented a large-scale pattern of leaf Chl among 677 site-species across grasslands on the Tibetan Plateau. Surprisingly, we found that plant evolutionary history was more dominant than current environmental changes in impacting the regional patterns of leaf Chl.…”