Response of leaf day respiration in C₄ plants to irradiance and vapour pressure deficit

Abstract

Leaf day respiration rate (R_L) plays a crucial role in the global carbon cycle. However, R_L of C₄ species has not been sufficiently studied and its response to environmental factors is largely unknown. This work studied the response of R_L of three C₄ species, Setaria viridis, Sorghum sudanense, and Zea mays, to alterations in the vapour pressure deficit (VPD) and irradiance of the growth environment. R_L was estimated using the Kok method (R_{L Kok}) and an improved method that combined gas exchange and chlorophyll fluorescence measurements (R_{L Yin}). On average, shade treatment led to a 24% reduction in R_{L Yin} and a 20% reduction in respiration in the dark (R_Dk), while a consistent VPD effect on R_L was not observed. R_L and R_Dk were positively correlated with nitrogen content per leaf area and net CO₂ assimilation rate but were not correlated with the capacity of carboxylation enzymes. We found a non-significant light inhibition of respiration (1 ± 2%), contradicting the assumption that respiration is inhibited by light and affected by light intensity. Our findings indicate that assuming R_L to be equal to R_Dk at the same temperature is a straightforward but reliable approach to model respiration of the examined C₄ species.

Keywords

C₄ photosynthesis / Chlorophyll fluorescence / Gas exchange / Irradiance / Respiration / Vapour pressure deficit

Abbreviations

A: net CO₂ assimilation rate

CaH: higher boundary CO₂ above which assimilation is limited by RuBP regeneration and PEP_c regeneration

CaL: lower boundary CO₂ above which assimilation is limited by RuBP regeneration and PEP_c regeneration

C_c: CO₂ concentration at the carboxylation sites of Rubisco

C_i: intercellular CO₂ concentration

C_m: mesophyll cell CO₂ concentration

E: transpiration rate

f_cyc: fractions of the total electron flux passing photosystem I (PSI) that follow cyclic pathways

f_pseudo: fractions of the total electron flux passing photosystem I (PSI) that follow pseudocyclic pathways

g_sw: stomatal conductance

I_inc: incident irradiance

J: the photosystem Ⅱ (PSII) electron transport rate used for photosynthesis

J₂: the total rate of electron transport passing PSII

J_atp: the rate of ATP production driven by electron transport

K_mC: Michaelis-Menten constants of Rubisco for CO₂

K_mO: Michaelis-Menten constants of Rubisco for O₂

K_p: the Michaelis-Menten constant of PEP_c for CO₂

LIR: the inhibition of respiration by light

N%: leaf nitrogen content

N_area: the N content on a leaf area basis

O_c: the O₂ partial pressure at the carboxylation sites of Rubisco

PEP_c: phosphoenolpyruvate carboxylase

R_Dk: leaf respiration in the dark

R_Dkm: dark respiration rate on a mass basis

R_L: leaf day respiration rate

R_{L Kok}: leaf day respiration rate estimated by Kok method

R_{L Kokm}: respiration rate in the light on a mass basis estimated by the Kok method

R_{L Yin}: leaf day respiration rate estimated by Yin method

R_{L Yinm}: respiration rate in the light on a mass basis estimated by the Yin method

S_c/o: the relative CO₂/O₂ specificity factor of Rubisco

SLA: specific leaf area

V_cmax: the maximum carboxylation rate of Rubisco

V_p: the rate of carboxylation for the C₄ cycle

VPD: vapour pressure deficit

V_pmax: the maximum carboxylation rate of PEP_c

β: the absorptance by leaf photosynthetic pigments

Γ∗: the C_c-based CO₂ compensation point in the absence of R_L

ρ₂: the proportion of absorbed irradiance partitioned to PSII

Φ₂: the photochemical efficiency of photosystem II

Availability of data and materials

Data will be shared upon request by the readers.

Authors' contributions

X.G. designed and planned the research. B.L. and Y.X. performed the experiment. B.L., X.W., and X.G. analysed the data and wrote the first draft. All authors discussed the results and implications and contributed to the revision.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (NSFC₃2120103005, 32201277) and the Natural Science Foundation of Fujian Province, China (2023J01289).

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.crope.2023.12.001.

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