Barillot, R. | bioRxiv Science

bioRxiv2025

Deciphering spatiotemporal patterns of rhizodeposition with a functional-structural root model: RhizoDep

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 soil-plant interactions. However, its spatial and temporal dynamics remain poorly understood. 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. 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. 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. HighlightUsing the new model RhizoDep, we simulated distinct spatial and temporal patterns of rhizodeposition along the roots of spring wheat over its complete growth cycle, and identified their main drivers. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=82 SRC="FIGDIR/small/646173v1_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@155786borg.highwire.dtl.DTLVardef@54c1b1org.highwire.dtl.DTLVardef@784ca9org.highwire.dtl.DTLVardef@1f0f09d_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2023

Effects of atmospheric CO2 concentration on transpiration and leaf elongation responses to drought in wheat, perennial ryegrass and tall fescue

We studied the effects of atmospheric CO2 concentration ([CO2]) on the leaf growth response to drought in perennial ryegrass, tall fescue and wheat. Plants were grown in growth chambers at either 200 or 800 ppm of CO2. At leaf 6-7 unfolding, half of the plants were subjected to severe drought. Leaf elongation rate (LER) was measured daily, while plant transpiration was continuously recorded gravimetrically. Water-soluble carbohydrate concentration, water and osmotic potentials in the leaf growing zone were measured at drought onset, at mid-drought and at the time of leaf growth cessation. [CO2] caused stomata closure and therefore reduction of instantaneous transpiration rate and water loss. As a result, CO2 mitigated the impacts of drought on LER and delayed growth cessation for all three species. For ryegrass, LER and soil relative water content (SRWC) relation was improved with CO2, presumably due to a better stomatal regulation. CO2 did not affect nighttime water potential nor osmotic potential of the growing zone. Related to leaf growth, we observed the main effect of CO2 on tillering but no effect on the plant development. In total, water consumption was similar (wheat, tall fescue) or greater (ryegrass) with CO2.

plant biology↗