It's only natural: Plant respiration in unmanaged systems

High-throughput screening of wheat leaf dark respiration identifies significant genetic control

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Gaju O, Bloomfield KJ, Negrini ACA, Bowerman AF, Cullerne D, Posch BC, Bryant C, Fan Y, Spence M, Stone B, Gilliham M, Furbank RT, Molero G, Pogson BJ, Mathews K, Millar AH, Pearson AL, Reynolds MP, Stroeher E, Taylor NL, Turnbull MH, Atkin OK. 2025. Accounting for the impact of genotype and environment on variation in leaf respiration of wheat in Mexico and Australia. Journal of Experimental Botany 76, 1099–1115. https://doi.org/10.1093/jxb/erae449.

New insights into the mechanisms of plant isotope fractionation from combined analysis of intramolecular 13C and deuterium abundances in Pinus nigra tree-ring glucose

Understanding isotope fractionation mechanisms is fundamental for analyses of plant ecophysiology and paleoclimate based on tree-ring isotope data. To gain new insights into isotope fractionation, we analysed intramolecular 13C discrimination in tree-ring glucose (Δi', i = C-1 to C-6) and metabolic deuterium fractionation at H1 and H2 (εmet) combinedly. This dual-isotope approach was used for isotope-signal deconvolution. We found evidence for metabolic processes affecting Δ1' and Δ3', which respond to air vapour pressure deficit (VPD), and processes affecting Δ1', Δ2', and εmet, which respond to precipitation but not VPD. These relationships exhibit change points dividing a period of homeostasis (1961-1980) from a period of metabolic adjustment (1983-1995). Homeostasis may result from sufficient groundwater availability. Additionally, we found Δ5' and Δ6' relationships with radiation and temperature, which are temporally stable and consistent with previously proposed isotope fractionation mechanisms. Based on the multitude of climate covariables, intramolecular carbon isotope analysis has a remarkable potential for climate reconstruction. While isotope fractionation beyond leaves is currently considered to be constant, we propose significant parts of the carbon and hydrogen isotope variation in tree-ring glucose originate in stems (precipitation-dependent signals). As basis for follow-up studies, we propose mechanisms introducing Δ1', Δ2', Δ3', and εmet variability.

Scaling of shoot and root respiration of woody and herbaceous plants

Woody and herbaceous plants are the main components of global terrestrial ecosystems, and their growth, adaptation and survival depend largely on the metabolism of shoots and roots. Therefore, understanding size-scaling of metabolic rates in woody and herbaceous plants, and in shoots and roots, is a fundamental issue in ecology. However, few empirical studies have examined metabolic scaling exponents across a wide range of plant sizes. Using whole-plant chamber systems, we measured respiration rates of entire root systems and shoots of 96 woody species (n = 1243) and 33 herbaceous species (n = 463) from various terrestrial biomes, with plant masses spanning nine orders of magnitude. Scaling exponents for relationships between respiration rates and fresh mass were greater in shoots than in roots, and both were greater in herbaceous plants than in woody plants. Furthermore, scaling of whole-plant respiration, including various species, converged separately for woody and herbaceous plants. These findings suggest some general physico-chemical constraints on energy use by shoots and roots of individual plants in various terrestrial biomes, including forests and grasslands. These data will advance our understanding of terrestrial ecosystem structure and function.

Changes in physio-biochemical metabolism, phenolics and antioxidant capacity during germination of different wheat varieties

Changes in physio-biochemical metabolism, phenolics and antioxidant capacity during germination were studied in eight different wheat varieties. Results showed that germination enhanced sprout growth, and caused oxidative damage, but enhanced phenolics accumulation. Ferulic acid and p-coumaric acid were the main phenolic acids in wheat sprouts, and dihydroquercetin, quercetin and vitexin were the main flavonoids. The phenolic acid content of Jimai 44 was the highest on the 2th and 4th day of germination, and that of Bainong 307 was the highest on the 6th day. The flavonoid content of Hei jingang was the highest during whole germination. The enzymes activities of phenylalanine ammonia lyase (PAL), cinnamic acid 4-hydroxylase (C4H) and 4-coumarate coenzyme A ligase (4CL) were up-regulated. The activities of catalase, polyphenol oxidase and peroxidase were also activated. Antioxidant capacity of wheat sprouts was enhanced. The results provided new ideas for the production of naturally sourced phenolic rich foods.

Respiration in light of evergreen and deciduous woody species and its links to the leaf economic spectrum

Leaf respiration in the light (Rlight) is crucial for understanding the net CO2 exchange of individual plants and entire ecosystems. However, Rlight is poorly quantified and rarely discussed in the context of the leaf economic spectrum (LES), especially among woody species differing in plant functional types (PFTs) (e.g., evergreen vs. deciduous species). To address this gap in our knowledge, Rlight, respiration in the dark (Rdark), light-saturated photosynthetic rates (Asat), leaf dry mass per unit area (LMA), leaf nitrogen (N) and phosphorus (P) concentrations, and maximum carboxylation (Vcmax) and electron transport rates (Jmax) of 54 representative subtropical woody evergreen and deciduous species were measured. With the exception of LMA, the parameters quantified in this study were significantly higher in deciduous species than in evergreen species. The degree of light inhibition did not significantly differ between evergreen (52%) and deciduous (50%) species. Rlight was significantly correlated with LES traits such as Asat, Rdark, LMA, N and P. The Rlight vs. Rdark and N relationships shared common slopes between evergreen and deciduous species, but significantly differed in their y-intercepts, in which the rates of Rlight were slower or faster for any given Rdark or N in deciduous species, respectively. A model for Rlight based on three traits (i.e., Rdark, LMA and P) had an explanatory power of 84.9%. These results show that there is a link between Rlight and the LES, and highlight that PFTs is an important factor in affecting Rlight and the relationships of Rlight with Rdark and N. Thus, this study provides information that can improve the next generation of terrestrial biosphere models (TBMs).