bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2023.07.21.549999

Consistent decrease in conifer embolism resistance from the stem apex to base resulting from axial trends in tracheid and pit traits

Zambonini, D.·Savi, T.·Rosner, S.·Petit, G.
View original source ↗Export metadata ↓

Abstract

Drought-induced embolism formation in conifers is associated with several tracheid and pit traits, which vary in parallel from stem apex to base. We tested whether this axial anatomical variability is associated with a progressive variation in embolism vulnerability along the stem from apex to base. We assessed the xylem pressure at 50% loss of conductivity (P50), the tracheid hydraulic diameter (Dh) and mean pit membrane area (PMA) on longitudinal stem segments extracted at different distances from the stem apex (DFA) in a Picea abies and an Abies alba tree. In both trees, Dh and PMA scaled with DFA0.2. P50 varied for more than 3 MPa from the treetop to the stem base, according to a scaling of -P50 with DFA-0.2. The largest Dh, PMA and P50 variation occurred for DFA<1.5 m. PMA and Dh scaled isometrically (exponent b=1). Pit traits vary proportionally with tracheid lumen diameter. Apex-to-base trends in tracheid and pit traits determine a large DFA-dependent P50 variability. Such a DFA effect on P50 did not receive sufficient attention so far, although analysing the relationships P50 vs. DFA is fundamental for the assessment of embolism vulnerability at the individual level. HighlightsO_LIConifer embolism vulnerability depends on pit properties, in agreement with published data. C_LIO_LIPit dimensions increase with tracheid lumen diameter, in agreement with published data C_LIO_LITracheid lumen diameter and pit dimensions increase progressively from the stem apex to base, in agreement with published data. C_LIO_LIXylem vulnerability to embolism formation (P50) varies for > 3 MPa from the stem apex to base, with the largest variation occurring within 1.5 m from the stem apex. C_LIO_LIAxial anatomical patterns should be accounted for when analyzing hydraulic properties at individual, intra- and inter-specific scales. C_LI

Explore related subjects

plant biologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Zambonini, D., Savi, T., Rosner, S., Petit, G.. 2023-07-25. Consistent decrease in conifer embolism resistance from the stem apex to base resulting from axial trends in tracheid and pit traits. https://doi.org/10.1101/2023.07.21.549999

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

AtNHR2A and AtNHR2B participate in unconventional protein secretion in response to environmental stress

The Arabidopsis thaliana nonhost resistance proteins 2A (AtNHR2A) and 2B (AtNHR2B) play crucial roles in plant immunity as the single mutants Atnhr2a and Atnhr2b and the double mutant Atnhr2bAtnhr2a are susceptible to the non-adapted pathogen Pseudomonas syringae pv. tabaci that is unable to infect wild-type Col-0 plants. The localization of fluorescent versions of AtNHR2A and AtNHR2B to compartments of the endomembrane system together with their interaction with secreted proteins suggested a function in endomembrane-mediated secretory processes participating in plant immunity. Comparative apoplastic proteomics analysis between wild type Col-0 and the double mutant Atnhr2bAtnhr2a after treatment P. syringae pv. tabaci, revealed that AtNHR2A and AtNHR2B are indeed required for the secretion of proteins containing N-terminal signal peptides that occurs through the conventional protein secretion pathway. In this work, we leveraged these apoplastic proteomics datasets to identify proteins lacking N-terminal signal peptide and expected to be secreted through unconventional secretion pathway(s). We discovered that AtNHR2A and AtNHR2B are also required for the secretion of proteins through an unconventional secretion pathway that, intriguingly, included proteins previously associated with abiotic stress. These findings led us to define the subcellular dynamics of AtNHR2A and AtNHR2B, and through co-localization analyses and the use of vesicle trafficking inhibitors, we uncovered their trafficking pathways transitioning through Golgi-dependent and Golgi-independent pathways to ultimately reach the central vacuole. Our findings suggest that AtNHR2A and AtNHR2B participate in a multivesicular bodies-vacuole-mediated unconventional secretion pathway that results in the release of proteins involved in plant responses to environmental stresses.

plant biology↗
bioRxiv2026

Low-cost rhizotron imaging and zero-shot deep-learning resolve temporal, spatial, and genetic variation in grapevine rootstock root systems

Root system architecture shapes how grapevine rootstocks take up water and nutrients, yet roots remain the least phenotyped grapevine organ because they are hidden and hard to image. We present a low-cost phenotyping pipeline that pairs custom acrylic rhizotrons (about US$30 each) with a consumer flatbed scanner and BiRefNet, a general-purpose deep-learning model used without training on root images, followed by automated mask cleaning, skeleton-based trait extraction, and soil moisture mapping. We tested it on nine commercial rootstocks scanned 16 times over 42 days after transplanting (DAT), with half under a ten-day water deficit. From 1,108 images we extracted 21 whole-root, depth-resolved, and topological traits. Genotypes differed in nearly every trait and in how they changed over time. Heritability of size and branching traits peaked at 0.92-0.93 between 21 and 31 DAT and fell for width, depth, and convex hull once roots reached the rhizotron walls, defining the best measurement window. The image-derived soil moisture map accurately tracked the deficit and its recovery. Deficit plants shifted new root growth to deeper soil without growing less overall, and the substrate dried fastest around older and denser roots. Root brightness decreased with root age and local moisture, and transport segments (axes serving several tips) were brighter than terminal laterals in every genotype. Root system size was associated with stomatal conductance in well-watered plants, and stomatal recovery after re-watering correlated with new root growth. The pipeline turns simple hardware into a quantitative, time-resolved root phenotyping platform suitable for breeding.

plant biology↗
bioRxiv2026

Engineering chromatin to encode transcriptional immune memory in Arabidopsis

Transcriptional memory enables organisms to respond more rapidly to recurrent stress, yet the underlying features of chromatin that contribute to this transcriptional recalibration remain poorly defined. Here we identify the genes displaying transcriptional memory in response to the bacterial immune elicitor, flg22, in Arabidopsis thaliana. In comparison to non-memory response genes, these memory genes show a preference for tissue-specific over uniform spatial expression patterning. The chromatin architecture of these genes in the resting state displays depletion of H3K4me3, elevation H3K27me3 and a subset are marked by H3K27me3-H3K4me3 bivalency. The H3K4me3 demethylase, JMJ14, is required for transcriptional memory, with JMJ14 occupancy enriched over memory gene loci. Upon priming, chromatin is reconfigured, with H3K4me3 levels increasing in a sustained manner at memory gene loci. To assess the function of this H3K4me3 accrual, we employ epigenome-engineering, observing that its targeted deposition at memory gene loci, including the WRKY29 locus, is sufficient to drive transcriptional memory and can endow plants with enhanced resistance to the bacterial pathogen, Pseudomonas syringae. Together, the findings demonstrate a causal role for H3K4me3 in transcriptional memory, under the regulation of JMJ14, and open the door for rational rewriting of chromatin to enhance organismal resilience.

plant biology↗