Unité de Recherche Pluridisciplinaire Prairies et Plantes Fourragères

Seed germination is a critical developmental stage susceptible to environmental factors, such as temperature and soil water potential, which directly influence germination percentage and rate. To gain deeper insight into these interactions, this study re-analyzed data from a previously published germination experiment involving six distinct sesame (Sesamum indicum L.) cultivars with varied fatty acid profiles. Germination was recorded across eight constant temperatures (10–45 °C) and seven water potential levels (0 to −1.2 MPa), using thermal time, hydrotime, and hydrothermal time models. No germination occurred at −1.0 or −1.2 MPa. The highest thermal time constant, θT(g), was observed at −0.8 MPa across all cultivars, and germination rates declined as water potential decreased. Hierarchical clustering based on principal component analysis grouped the cultivars into three distinct clusters. Cluster 1, containing two cultivars, exhibited the highest base temperatures (above 13 °C), which correlated with high arachidic and low linolenic acid content. The three cultivars in cluster 2 showed the highest hydrothermal time constants (θHT(g) = 760–2495 MPa·°C·h) and contrasting palmitic and stearic acid profiles. The single cultivar in cluster 3 had the lowest base water potential, the highest oleic acid content, and the highest percentage of linoleic acid. These findings underscore the significant role of seed fatty acid composition in stress tolerance, with ‘Darab1’ showing superior drought resistance and ‘Dashtestan2’ showing greater resilience to high temperatures. These modeling and multivariate analyses provide deeper insights into germination mechanisms and offer valuable guidance for selecting cultivars adapted to specific climatic conditions.

Abstract Background and Aims Rhizodeposition, i.e. the release of organic matters by roots, constitutes a significant fraction of the plant carbon (C) budget and plays a key role in plant-soil interactions. However, its spatial and temporal dynamics remain poorly understood. Methods We developed RhizoDep, a new functional-structural root model that simulates 3D root growth, respiration, and rhizodeposition based on C balance and root morphology at the individual root segment level. Results Our model successfully reproduced the dynamics of belowground C flows observed in a previous pulse-labelling field experiment on spring wheat. Our simulations revealed that root C exudation largely dominated over mucilage secretion and cap cells sloughing in terms of C release. The spatial distribution of exudation rate along the roots was driven by the preferential unloading of sugars to support root elongation and emergence, and was modulated by the formation of apoplastic barriers. Furthermore, our results demonstrated that, for a given C allocation flow to roots, variations in root hairs or lateral root number had minimal effects on rhizodeposition, whereas changes in root tissue density had a significant impact. Conclusion RhizoDep offers a new opportunity to explore the dynamics of C exchange at the plant-soil interface and to identify traits and environmental conditions that favor rhizodeposition.

International audience

Since their inception, the French academic organizations dedicated to agricultural research have developed plant collections in genebanks, often within a public–private framework, to support the study of plant traits and the development of new improved varieties. In addition, since the 2000s, a centre for genomic resources has also been established in France. Over the last 20 years, this decentralized system, consisting of the academic genebanks and the centre for genomic resources, has been supported by a national coordination structure. The objectives were to align the network activities with the framework proposed by the Organisation for Economic Co-operation and Development (OECD) for Biological Resource Centres and to foster collaboration with other national stakeholders involved in the conservation and characterization of plant genetic resources (PGR). In 2015, the network was named BRC4Plants and become part of the French National Research Infrastructure RARe (www.agrobrc-rare.org), supported by the French Ministry of Research. This paper describes BRC4Plants, its users, services and cross-cutting activities. We also highlight its relations with its national and international stakeholders involved in the conservation and characterization of PGRs. BRC4Plants aims to be a key player in addressing societal and research challenges regarding agroecology, climate change mitigation and healthy food systems.

ABSTRACT Microbial transformation of soil organic matter plays a critical role in carbon (C) cycling making it essential to understand how land use and management practices influence microbial physiology and its connection to C dynamics. One factor that is likely to impact soil microbial physiology is crop diversification via its influence on belowground diversity (e.g., chemical heterogeneity of C inputs, microbial community composition). However, the effect of crop diversification measures on microbial physiology and potential effects on C cycling in agricultural soils is still unclear. To address this knowledge gap, we sampled topsoil from eight experimental sites covering different crop diversification measures across Europe (i.e., cover crops, ley farming, vegetation stripes). We used the 18 O‐labelling method to analyse microbial C use efficiency (CUE), growth, respiration and biomass C. Additionally, a second sampling at five selected sites examined whether the growing season influenced the impact of crop diversification. Meta‐analysis revealed no overall effect of crop diversification on CUE, microbial activity, biomass or soil organic C (SOC). However, the effects varied with the type of diversification measure: cover crops did not affect carbon processing, vegetation stripes increased microbial activity, and ley farming enhanced CUE. The largest variation in CUE was observed between samplings at the same sites, indicating seasonal dynamics. Temperature, precipitation and photosynthetically active radiation predicted seasonal variation in CUE ( R 2 = 0.36). While cover crops did not significantly impact C storage in our study, both ley farming and vegetation stripes increased SOC. The overall effect of crop diversification on SOC seems to be decoupled from highly temporally variable CUE in the bulk soil and rather relate to C‐inputs.

Forage maize is a central pillar of dairy cow feeding in France, directly influencing milk production. Drought significantly affects both maize yield and digestibility, which are both key parameters required for hybrid registration purposes. Research on maize inbred lines has revealed droughts' notable effect on dry matter and cell wall digestibilities due to changes in cell wall composition, directly impacting forage quality. No such studies have been performed on forage maize hybrids however, which are the main seed type used in the agricultural sector. In this paper, we aimed to understand the impact of water and heat stress on forage maize digestibility, and to uncover the factors controlling it. We grew a panel of eleven modern forage maize hybrids for two years under four different controlled water stress modalities. These plants were agronomically, biochemically and histologically assayed, allowing us to perform a multiscale analysis to determine the traits responsible for variations in digestibility. By establishing a comprehensive heat and water stress index, we classified the environmental conditions. We demonstrated that under severe stress, ear production decreases significantly, but dry matter digestibility can be maintained through increased cell wall digestibility. This boost in cell wall digestibility was due to a reduction in p-hydroxycinnamic acid content and changes in lignin distribution, while lignin content and structure remained stable. The significant impact of lignin distribution on cell wall digestibility increased with the severity of the stress, reaching an extreme threshold where biochemical parameters solely account for digestibility variations. To improve maize digestibility, it will be necessary to better understand how the reduction in carbon flux under stress affects p-hydroxycinnamic acid levels without greatly impacting lignin content. Finally, our work suggests that the inclusion of moderate stress conditions in future maize breeding programs will be necessary to better adapt forage maize hybrids to climate change.

Continuous agricultural activities lead to soil organic carbon (SOC) depletion, and agroecological intensification practices (i.e., reduced soil disturbance and crop diversification) have been suggested as strategies to increase SOC storage. The study aims to assess the effect of agroecological intensification levels (lower (T1) and highest (T2)) on the soil C pool and aggregate stability and validate the correlation between different variables compared to the control (lowest/none (T3), where agroecological intensification was not applied. The C-stock, soil microbial biomass carbon (SMB-C), SOC, water extractable organic carbon (WEOC) in bulk soil, fine and coarse soil aggregates, and water-stable aggregates (WSA) were measured during maximum nutrient uptake in plants under diversified agroecological practices across different environmental conditions (core sites: Italy (CS1), France (CS2), Denmark (CS4), Spain (CS5), Netherlands (CS6), Lithuania (CS7), Turkey (CS8), and Belgium (CS9)). The soil aggregate stability varied among the CSs and treatments. At sites CS7 and CS9, WSA was higher in T1 and T2 compared to the control; a similar trend was observed at other sites, except CS1. SMB-C differed among the core sites, with the lowest value obtained in CS5 (52.3 μg g−1) and the highest in CS6 (455.1 μg g−1). The highest average contents of SOC and WEOC were obtained in bulk soil at CS2 (3.1 % and 0.3 g kg−1 respectively). Positive and statistically significant (p < 0.001) correlations were detected among all variables tested with SOC in bulk soil and WSA. This study demonstrates the significance of agroecological practices in improving soil carbon stock and optimizing plant–soil–microbe interactions.