Biology subjects

Tcherkez, G.

Publications and source records attributed to Tcherkez, G..

4 recordsLinked to original sources

bioRxiv2026

Identification of Seed Metabolites and Microbiota members associated with Germination and Emergence in Common Bean

Seed quality is a complex trait shaped by morphological, biochemical and microbiological properties that are rarely characterised simultaneously, limiting our ability to identify robust predictive indicators of germination speed and seedling emergence across varieties. Here, we performed a multi-factor characterisation of eight common bean (Phaseolus vulgaris L.) varieties, combining seed morphometrics, untargeted GC-MS metabolomics on three seed organs, and amplicon sequencing of bacterial and fungal communities, to identify indicators of germination speed and emergence percentage. The eight varieties showed substantial variation in both traits, used as physiological seed quality proxies. Seed weight and size variation between varieties were correlated with germination speed. The intravariety variance of seed weight was independently correlated with emergence performance. Metabolome composition differed strongly across seed organs, with variety as the dominant driver. Individual-seed metabolomic profiles in the plumule and cotyledon were associated with germination speed but not emergence, yielding 16 plumule and three cotyledon candidate metabolite markers. Fungal community composition was associated with both germination speed and emergence, while bacterial communities were associated with emergence only. Nine fungal and four bacterial taxa were identified as candidate indicators. Inter-kingdom co-occurrence network analysis revealed that fungi with similar germination speed associations tend to cluster in the same modules, suggesting that community-level modules rather than individual taxa may constitute more robust microbial indicators. These results demonstrate that germination speed and emergence capacity are governed by distinct seed properties, and provide morphological, metabolic and microbial candidate indicators for integration into targeted seed quality assessment frameworks for common bean.

plant biology↗

bioRxiv2023

Leaf δ13C reveals post-photosynthetic fractionation during ontogeny in a C4 grass

The 13C isotope composition ({delta}13C) of leaf dry matter is a useful tool for physiological and ecological studies. However, how post-photosynthetic fractionation associated with respiration and carbon export influences {delta}13C remains uncertain. We investigated the effects of post-photosynthetic fractionation on {delta}13C of mature leaves of Cleistogenes squarrosa, a perennial C4 grass, in controlled experiments with different levels of vapour pressure deficit and nitrogen supply. With the increase of leaf age classes, the 12C/13C fractionation of leaf organic matter relative to the {delta}13C of atmosphere CO2 ({Delta}DM) increased while that of cellulose ({Delta}cel) was almost constant. The divergence between {Delta}DM and {Delta}cel increased with leaf age classes with a maximum value of 1.6{per thousand}, indicating the accumulation post-photosynthetic fractionation. Applying a new mass balance model that accounts for respiration and export of photosynthates, we found an apparent 12C/13C fractionation associated with carbon export of -0.5 to -1.0{per thousand}. Different {Delta}DM among leaves, pseudostems, daughter tillers and roots indicate that post-photosynthetic fractionation happens at the whole-plant level. Compared with {Delta}DM of old leaves, {Delta}DM of young leaves and {Delta}cel are more reliable proxies for predicting physiological parameters due to the smaller sensitivity to post-photosynthetic fractionation and the similar sensitivity in responses to environmental changes. BRIEF SUMMARY STATEMENT{Delta}13C of bulk organic matter increases with leaf age classes while {Delta}13C of cellulose remain constant, lending support to the use of {Delta}13C of cellulose as a more reliable proxy for predicting physiological parameters due to the smaller sensitivity to post-photosynthetic fractionation.

plant biology↗

bioRxiv2020

Revisiting the carbon isotope discrimination and water use efficiency relation: the influence of mesophyll conductance

SummaryThe carbon isotope discrimination (Δ) has been used widely to infer intrinsic water-use efficiency (iWUE) of C3 plants, a key parameter linking carbon and water fluxes. Despite the essential role of mesophyll conductance (gm) in photosynthesis and Δ, its effect on Δ-based predictions of iWUE has generally been neglected.Here, we derive a mathematical expression of iWUE as a function of Δ that includes gm (iWUEmes) and exploits the gm-stomatal conductance (gsc) relationship across drought-stress levels and plant functional groups (deciduous or semi-deciduous woody, evergreen woody and herbaceous species) in a global database. iWUEmes was further validated with an independent dataset of online-Δ and CO2 and H2O gas exchange measurements with seven species.Drought stress reduced gsc by 52% and gm by 45% averaged over all plant functional groups, but had no significant effect on the gsc/gm ratio, suggesting a well-constrained gsc/gm ratio of 0.79±0.07 (95%CI, n=198) across plant functional groups and drought-stress treatments. Due in part to the synchronous behavior of gsc and gm, gm was negatively correlated to iWUE. Incorporating the gsc/gm ratio in the iWUEmes model significantly improved the estimation of iWUE compared to the simple model.The inclusion of gm effects, even using a fixed gsc/gm ratio of 0.79 when gm is unknown, proved desirable to eliminate significant bias in estimating iWUE from Δ across various C3 vegetation types.Competing Interest StatementThe authors have declared no competing interest.View Full Text

plant biology↗

bioRxiv2017

Measurement of leaf day respiration using a new isotopic disequilibrium method compared with the Laisk method

O_LIQuantification of leaf respiration is of great importance for the understanding of plant physiology and ecosystem biogeochemical processes. Leaf respiration continues in light (RL) but supposedly at a lower rate compared to the dark (RD). Yet, there is no method for direct measurement of RL and most available methods require unphysiological measurement conditions.\nC_LIO_LIA method based on isotopic disequilibrium quantified RL (RL 13C) and mesophyll conductance of young and old fully-expanded leaves of six species compared RL 13C to RL values determined by the Laisk method (RL Laisk).\nC_LIO_LIRL 13C and RL Laisk were consistently lower than RD. Leaf ageing negatively affected photosynthetic performance, but had no significant effect on RL or RL/RD as determined by both methods. RL Laisk and RL 13C were measured successively on the same leaves and correlated positively (r2=0.38), but average RL Laisk was 28% lower than RL13C. Using A/Cc curves instead of A/Ci curves, a higher photocompensation point {Gamma}* (by 5 mol mol-1) was found but the correction had no influence on RL Laisk estimates.\nC_LIO_LIThe results suggest that the Laisk method underestimated RL. The isotopic disequilibrium method is useful for assessing responses of RL to irradiance and CO2, improving our mechanistic understanding of RL.\nC_LI

plant biology↗