Wall Growth Research Articles

The Arabidopsis xylosyltransferases, XXT3, XXT4, and XXT5, are essential to complete the fully xylosylated glucan backbone XXXG-type structure of xyloglucans.

Although most xyloglucans (XyGs) biosynthesis enzymes have been identified, the molecular mechanism that defines XyG branching patterns is unclear. Four out of five XyG xylosyltransferases (XXT1, XXT2, XXT4, and XXT5) are known to add the xylosyl residue from UDP-xylose onto a glucan backbone chain; however, the function of XXT3 has yet to be demonstrated. Single xxt3 and triple xxt3xxt4xxt5 mutant Arabidopsis (Arabidopsis thaliana) plants were generated using CRISPR-Cas9 technology to determine the specific function of XXT3. Combined biochemical, bioinformatic, and morphological data conclusively established for the first time that XXT3, together with XXT4 and XXT5, adds xylosyl residue specifically at the third glucose in the glucan chain to synthesize XXXG-type XyGs. We propose that the specificity of XXT3, XXT4, and XXT5 is directed toward the prior synthesis of the acceptor substrate by the other two enzymes, XXT1 and XXT2. We also conclude that XXT5 plays a dominant role in the synthesis of XXXG-type XyGs, while XXT3 and XXT4 complementarily contribute their activities in a tissue-specific manner. The newly generated xxt3xxt4xxt5 mutant produces only XXGG-type XyGs, which further helps to understand the impact of structurally deficient polysaccharides on plant cell wall organization, growth, and development.

Quantitative analysis of morphogenesis and growth dynamics in an obligate intracellular bacterium.

Obligate intracellular bacteria of the order Rickettsiales include important human pathogens. However, our understanding of the biology of Rickettsia species is limited by challenges imposed by their obligate intracellular lifestyle. To overcome this roadblock, we developed methods to assess cell wall composition, growth, and morphology of Rickettsia parkeri, a human pathogen in the spotted fever group of the Rickettsia genus. Analysis of the cell wall of R. parkeri revealed unique features that distinguish it from free-living alphaproteobacteria. Using a novel fluorescence microscopy approach, we quantified R. parkeri morphology in live host cells and found that the fraction of the population undergoing cell division decreased over the course of infection. We further demonstrated the feasibility of localizing fluorescence fusions, for example, to the cell division protein ZapA, in live R. parkeri for the first time. To evaluate population growth kinetics, we developed an imaging-based assay that improves on the throughput and resolution of other methods. Finally, we applied these tools to quantitatively demonstrate that the actin homologue MreB is required for R. parkeri growth and rod shape. Collectively, a toolkit was developed of high-throughput, quantitative tools to understand growth and morphogenesis of R. parkeri that is translatable to other obligate intracellular bacteria.

Directed growth and fusion of membrane-wall microdomains requires CASP-mediated inhibition and displacement of secretory foci

Casparian strips (CS) are aligned bands of lignin-impregnated cell walls, building an extracellular diffusion barrier in roots. Their structure profoundly differs from tight junctions (TJ), analogous structures in animals. Nonetheless, CS membrane domain (CSD) proteins 1-5 (CASP1-5) are homologues of occludins, TJ components. CASP-marked membranes display cell wall (matrix) adhesion and membrane protein exclusion. A full CASP knock-out now reveals CASPs are not needed for localized lignification, since correctly positioned lignin microdomains still form in the mutant. Ultra-structurally, however, these microdomains are disorganized, showing excessive cell wall growth, lack of exclusion zone and matrix adhesion, and impaired exocyst dynamics. Proximity-labelling identifies a Rab-GTPase subfamily, known exocyst activators, as potential CASP-interactors and demonstrate their localization and function at the CSD. We propose that CASP microdomains displace initial secretory foci by excluding vesicle tethering factors, thereby ensuring rapid fusion of microdomains into a membrane-cell wall band that seals the extracellular space.

A multiscale framework for defining homeostasis in distal vascular trees: applications to the pulmonary circulation.

Pulmonary arteries constitute a low-pressure network of vessels, often characterized as a bifurcating tree with heterogeneous vessel mechanics. Understanding the vascular complexity and establishing homeostasis is important to study diseases such as pulmonary arterial hypertension (PAH). The onset and early progression of PAH can be traced to changes in the morphometry and structure of the distal vasculature. Coupling hemodynamics with vessel wall growth and remodeling (G&R) is crucial for understanding pathology at distal vasculature. Accordingly, the goal of this study is to provide a multiscale modeling framework that embeds the essential features of arterial wall constituents coupled with the hemodynamics within an arterial network characterized by an extension of Murray's law. This framework will be used to establish the homeostatic baseline characteristics of a pulmonary arterial tree, including important parameters such as vessel radius, wall thickness and shear stress. To define the vascular homeostasis and hemodynamics in the tree, we consider two timescales: a cardiac cycle and a longer period of vascular adaptations. An iterative homeostatic optimization, which integrates a metabolic cost function minimization, the stress equilibrium, and hemodynamics, is performed at the slow timescale. In the fast timescale, the pulsatile blood flow dynamics is described by a Womersley's deformable wall analytical solution. Illustrative examples for symmetric and asymmetric trees are presented that provide baseline characteristics for the normal pulmonary arterial vasculature. The results are compared with diverse literature data on morphometry, structure, and mechanics of pulmonary arteries. The developed framework demonstrates a potential for advanced parametric studies and future G&R and hemodynamics modeling of PAH.

RECONSTRUCTION OF GASTROINTESTINES AND ADJACENT STRUCTURES IN THE EARLY PERIOD OF HUMAN ONTOGENESIS

The article describes the laying periods of: the stomach (embryos 4.5-5.0 mm long), the circular layer of the muscle membrane; gastric pits (embryos 14.7-15.0 mm long); gastric glands are formed in pre-fruits with a length of 66.0-68.0 mm. On the basis of graphic and computer reconstruction, the rotation of the stomach around the longitudinal axis of the embryo, the relationship of the stomach with neighboring structures – the liver, gall bladder, duodenum and pancreas – are studied. The fetal stomach undergoes heterogeneous and multifactorial rotation as a result of increased growth of the stomach wall on the left and increased gastric motility caused by the previous increase in the mesentery, and that the direction of rotation is determined by the forces exerted on the stomach and gastric mesentery by neighboring organs. The shape of the stomach is caused by a change in the dorsal-left sections of the tab, which leads to rapid growth compared to the ventroright sections. The cranial part of the stomach is wider than the caudal part. Uneven growth is observed not only in transverse, but also in cranial directions. The cranial part of the stomach is wider than the caudal part. A signifi cant change in the stomach occurs during 7.5 to 8.5 weeks. Due to the protrusion of the upper part of the large curvature, the bottom is formed. In an embryo of 4.5 weeks, the lumen of the loops of the proximal part of the intestinal tube has an oval shape and slightly exceeds that of the caudal part of the digestive tract. the topographical relationship of the stomach with the surrounding organs changes signifi cantly during the prenatal period of development. In embryos of 4.5-8.0 mm, the lining of the stomach is located deep behind the liver, which surrounds it on three sides. Dorsal to the stomach lining are the lining of the left adrenal gland, the left mesonephros, and the lining of the spleen. Cranially, the lining of the stomach abuts the lung to the left. At the end of the prenatal period, the diameters of the portal of the stomach, the portal canal, the bulb of the duodenum, the length of the portal canal along the lesser curvature and the portal canal along the greater curvature, and the size of the angle of the stomach were determined.

Performance of Biomass and Exopolysaccharide Production from the Medicinal Mushroom Ganoderma lucidum in a New Fabricated Air-L-Shaped Bioreactor (ALSB)

Conventional stirred-tank bioreactor (STR) designs are optimised for cultures of bacteria but not fungal cultures; therefore, a new Air-L-Shaped Bioreactor (ALSB) was fabricated. The ALSB was designed to eliminate the wall growth and clumping of fungal mycelium in STRs. Ganoderma lucidum was used as a fungal model and its biomass and exopolysaccharide (EPS) production were maximised by optimising the agitation rate, glucose concentration, initial pH, and aeration via response surface methodology (RSM). The ALSB system generated 7.8 g/L of biomass (biomass optimised conditions: 110 rpm, 24 g/L glucose, pH 5.6, and 3 v/v of aeration) and 4.4 g/L of EPS (EPS optimised conditions: 90 rpm, 30 g/L glucose, pH 4, and 2.5 v/v of aeration). In combination, for both optimised conditions, biomass (7.9 g/L) and EPS (4.6 g/L) were produced at 110 rpm, 30 g/L glucose, pH 4, and 3 v/v of aeration with minimal wall growth. The data prove that the ALSB is a blueprint for efficient economical fungal cultivation.

The global regulator FpLaeB is required for the regulation of growth, development, and virulence in Fusarium pseudograminearum.

Fusarium pseudograminearum is a soil-borne pathogen that is capable of causing a highly destructive crown disease in wheat. Secondary metabolites (SMs), especially deoxynivalenol (DON), are the primary virulence factors during infection. Here, we characterised the global regulator FpLaeB, an orthologue of LaeB protein function, to regulate the SM in Aspergillus nidulans. Through the utility of the gene targeting approach, we found that the vegetative growth of the FpLaeB deletion mutant was drastically reduced compared to that of the wild type. FpLaeB was also important for conidiation because the FpLaeB deletion mutant formed fewer conidia in induced medium. In addition, the sensitivity of the FpLaeB deletion mutant to the cell wall integrity inhibitor was decreased, while its growth was more severely inhibited by the cell membrane inhibitor sodium dodecyl sulfate (SDS) than that of the wild type. More importantly, the virulence was decreased when the FpLaeB deletion mutant was inoculated onto the wheat stem base or head. Through genome-wide gene expression profiling, FpLaeB was found to regulate several processes related to the above phenotypes such as the carbohydrate metabolic process, which is an integral and intrinsic component of membranes, especially SMs. Furthermore, the generation of DON was impaired in the FpLaeB deletion mutant via ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) assay. These results showed that FpLaeB plays an important role in the growth, development, and maintenance of the cell wall, and in membrane integrity. More importantly, FpLaeB is required for SMs and full virulence in F. pseudograminearum.

Inhibitory effect of carvacrol against Alternaria alternata causing goji fruit rot by disrupting the integrity and composition of cell wall.

Goji (Lycium barbarum L.) is a widely planted crop in China that is easily infected by the pathogenic fungus Alternaria alternata, which causes rot after harvest. Previous studies showed that carvacrol (CVR) significantly inhibited the mycelial growth of A. alternata in vitro and reduced Alternaria rot in goji fruits in vivo. The present study aimed to explore the antifungal mechanism of CVR against A. alternata. Optical microscopy and calcofluor white (CFW) fluorescence observations showed that CVR affected the cell wall of A. alternata. CVR treatment affected the integrity of the cell wall and the content of substances in the cell wall as measured by alkaline phosphatase (AKP) activity, Fourier transform-infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Chitin and β-1,3-glucan contents in cells decreased after CVR treatment, and the activities of β-glucan synthase and chitin synthase decreased. Transcriptome analysis revealed that CVR treatment affected cell wall-related genes in A. alternata, thereby affecting cell wall growth. Cell wall resistance also decreased with CVR treatment. Collectively, these results suggest that CVR may exert antifungal activity by interfering with cell wall construction, leading to impairment of cell wall permeability and integrity.

High-density genetic linkage mapping reveals low stability of QTLs across environments for economic traits in Eucalyptus.

Eucalyptus urophylla, E. tereticornis and their hybrids are the most important commercial forest tree species in South China where they are grown for pulpwood and solid wood production. Construction of a fine-scale genetic linkage map and detecting quantitative trait loci (QTL) for economically important traits linked to these end-uses will facilitate identification of the main candidate genes and elucidate the regulatory mechanisms. A high-density consensus map (a total of 2754 SNPs with 1359.18 cM) was constructed using genotyping by sequencing (GBS) on clonal progenies of E. urophylla × tereticornis hybrids. QTL mapping of growth and wood property traits were conducted in three common garden experiments, resulting in a total of 108 QTLs. A total of 1052 candidate genes were screened by the efficient combination of QTL mapping and transcriptome analysis. Only ten QTLs were found to be stable across two environments, and only one (qSG10Stable mapped on chromosome 10, and associated with lignin syringyl-to-guaiacyl ratio) was stable across all three environments. Compared to other QTLs, qSG10Stable explained a very high level of phenotypic variation (18.4-23.6%), perhaps suggesting that QTLs with strong effects may be more stably inherited across multiple environments. Screened candidate genes were associated with some transcription factor families, such as TALE, which play an important role in the secondary growth of plant cell walls and the regulation of wood formation. While QTLs such as qSG10Stable, found to be stable across three sites, appear to be comparatively uncommon, their identification is likely to be a key to practical QTL-based breeding. Further research involving clonally-replicated populations, deployed across multiple target planting sites, will be required to further elucidate QTL-by-environment interactions.

PELATIHAN KADER POSYANDU MENGGUNAKAN KMS DINDING UNTUK DETEKSI ANAK STUNTING DI DESA PASAR MIRING KECAMATAN PAGAR MERBAU, DELI SERDANG

The prevalence of Stunting of children in developing countries is still high including Indonesia. Basic health research Riskesdas, 2013 found that 37.2% were stunted. To detect stunting, community empowerment team used Height Score growth chart. Previous research found that this chart had high sensitivity and specificity. The purpose of this study to improve skill of posyandu caders in using wall growth chart and determine nutritional status of children.
 A total of 25 Posyandu cadres were trained on the application of wall growth chart. Caders skill was evaluated by five components; pus the chart on the wall, validation, posing the children, detemine height dan determine nutritional status.
 Of the 36 children 25% of them was stunteded, 25% was rather stunting and 50% was normal. Conclusion. Wall growth chart was effective in detecting stunted children in Posyandu.

Complications of Growing Rod Technique for Early Onset Scoliosis

Early onset scoliosis (EOS) is defined as scoliosis occurring in children less than 10 years of age. The EOS is a separate entity of discussion as development of lungs is restricted due to restricted growth of the chest wall, unlike in adolescent scoliosis which is more of a cosmetic problem. Therefore, in EOS, control of deformity at early stage and growth of the spine should go hand-in-hand. The most favored option in recent era is growing rods which allow growth of the spine but in a controlled manner. However due to fusionless nature, these techniques have high rate of complications. The complications primarily include implant related, wound related, and anesthetic complications. Recently impact of multiple surgeries on psychology of developing child has been reported. This narrative reviews the literature about complications associated with growing rod surgeries in EOS.

Localized growth distribution on the abdominal aortic aneurysm surface using deep learning approaches

An abdominal aortic aneurysm (AAA) is a dangerous pathology that needs regular monitoring based on medical images. Currently, only visual estimates of the growth rate and methods based on the assessment of changes in the maximum diameter of the aneurysm in clinical practice are used. However, the quantitative assessment of vessel wall growth rate based on deformable image registration is gaining popularity in research. This paper presents a study of the applicability of the neural network approach of image registration for the quantitative growth assessment problem. In this study, we analyzed classical and neural network methods of image registration and used VoxelMorph and HyperMorph neural network architectures to evaluate local AAA growth based on the available dataset. Also, we compared the results of the obtained maximum local deformations of the AAA with the method of estimating the change in the maximum diameter.

Origin of congenital coronary arterio-ventricular fistulae from anomalous epicardial and myocardial development

Coronary Artery Fistulae (CAFs) are cardiac congenital anomalies consisting of an abnormal communication of a coronary artery with either a cardiac chamber or another cardiac vessel. In humans, these congenital anomalies can lead to complications such as myocardial hypertrophy, endocarditis, heart dilatation, and failure. Unfortunately, despite their clinical relevance, the aetiology of CAFs remains unknown. In this work, we have used two different species (mouse and avian embryos) to experimentally model CAFs morphogenesis. Both conditional Itga4 (alpha 4 integrin) epicardial deletion in mice and cryocauterisation of chick embryonic hearts disrupted epicardial development and ventricular wall growth, two essential events in coronary embryogenesis. Our results suggest that myocardial discontinuities in the embryonic ventricular wall promote the early contact of the endocardium with epicardial-derived coronary progenitors at the cardiac surface, leading to ventricular endocardial extrusion, precocious differentiation of coronary smooth muscle cells, and the formation of pouch-like aberrant coronary-like structures in direct connection with the ventricular lumen. The structure of these CAF-like anomalies was compared with histopathological data from a human CAF. Our results provide relevant information for the early diagnosis of these congenital anomalies and the molecular mechanisms that regulate their embryogenesis.

Localized growth and remodelling drives spongy mesophyll morphogenesis.

The spongy mesophyll is a complex, porous tissue found in plant leaves that enables carbon capture and provides mechanical stability. Unlike many other biological tissues, which remain confluent throughout development, the spongy mesophyll must develop from an initially confluent tissue into a tortuous network of cells with a large proportion of intercellular airspace. How the airspace in the spongy mesophyll develops while the tissue remains mechanically stable is unknown. Here, we use computer simulations of deformable polygons to develop a purely mechanical model for the development of the spongy mesophyll tissue. By stipulating that cell wall growth and remodelling occurs only near void space, our computational model is able to recapitulate spongy mesophyll development observed in Arabidopsis thaliana leaves. We find that robust generation of pore space in the spongy mesophyll requires a balance of cell growth, adhesion, stiffness and tissue pressure to ensure cell networks become porous yet maintain mechanical stability. The success of this mechanical model of morphogenesis suggests that simple physical principles can coordinate and drive the development of complex plant tissues like the spongy mesophyll.

Non-autonomous chemostat models with non-monotonic growth

In this paper, we investigate four non-autonomous chemostat models with non-monotonic consumption function, where wall growth and nutrient recycling are also taken into account. In each case, we prove the existence and uniqueness of non-negative global solution that generates a non-autonomous dynamical system. In addition, we also prove the existence of a unique (global) pullback attractor whose internal structure provides detailed information about the long-time behaviour of the state variables, for instance, conditions to ensure the extinction and the persistence of the species. We also display numerical simulations to illustrate the theoretical results.

Exogenous Melatonin Regulates Puberty and the Hypothalamic GnRH-GnIH System in Female Mice.

In recent years, the age of children entering puberty is getting lower and the incidence of central precocious puberty is increasing. It is known that melatonin plays an increasingly important role in regulating animal reproduction, but the specific role and mechanism of melatonin in regulating the initiation of puberty remain unclear. The purpose of the current study was to investigate the effect of subcutaneous melatonin injection on pubertal development in female mice and its mechanism of action. Female mice that were 22 days old received 1 mg/kg doses of melatonin subcutaneously every day for 10, 15 and 20 days. The vaginal opening was checked daily. Hematoxylin and eosin (HE) stain was used to determine the growth of the uterus and ovaries. Enzyme-linked immunosorbent assay (ELISA) was used to determine the levels of follicle-stimulating hormone (FSH), gonadotropin-inhibiting hormone (GnIH), and gonadotropin-releasing hormone (GnRH) in serum. By using RT-PCR and Western blotting, the mRNA and protein expression of the hypothalamus GnRH, GnIH, Kisspeptin (Kp), Proopiomelanocortin (POMC), Neuropeptide Y (NPY), as well as G protein-coupled receptor 147 (GPR147) were identified. The findings demonstrated that melatonin could suppress ovarian follicle and uterine wall growth as well as delay vaginal opening, decrease serum levels of GnRH and FSH and increase levels of GnIH. Melatonin increased GnIH and GPR147 expression in the hypothalamus in comparison to the saline group, while decreasing the expression of GnRH, Kisspeptin, POMC, and NPY. In conclusion, exogenous melatonin can inhibit the onset of puberty in female mice by modulating the expression of hypothalamic GnRH, GnIH, Kisspeptin, POMC and NPY neurons and suppressing the hypothalamic-pituitary-gonadal axis.

Seasonal variations in microbial diversity and metabolite profiles of the gut of sea cucumber (Apostichopus japonicus)

The sea cucumber (Apostichopus japonicus) is the main economic species in China and has a significant role in aquaculture. Gut microbiome composition is closely related to external environments. In this study, we identified the effects of seasonal changes on the composition and main metabolites of symbiotic microorganisms in the intestine of A. japonicus. We used 16S rRNA sequencing to identify the composition of symbiotic microorganisms in different seasons. Intestinal metabolites were determined using liquid chromatography with tandem mass spectrometry, which linked symbiotic microorganisms to intestinal metabolites. Analyzing changes in intestinal microbial composition across different seasons. The results showed that seasonal changes of intestinal microorganisms were significant, A. japonicus were infected by Vibrio easily in summer, Stigmasterol and sitosterol could affect the growth of body wall of A. japonicus. It is vital importance for A. japonicus that the results benefit for the growth, immunity and aquaculture.

PSAT123 Pheochromocytoma Resection and Coronary Artery Bypass Surgery: Chicken or the Egg??? - A Case Report

Abstract Introduction Pheochromocytoma (PCC) is a rare catecholamine-secreting neuroendocrine tumor with an incidence of 8 per million person-years. Advanced Coronary artery disease (CAD) and PCC may coexist secondary to chronic sympathetic activation, resulting in irreversible vascular wall growth and accelerated vascular atherosclerosis. The hemodynamic management of this association often represents a challenging dilemma due to the dramatic consequences of the hypertensive crisis caused by excessive catecholamine release. here we present a case of concomitant triple vessel disease and PCC to shed a light on our sequence of management to help guide providers as currently due to the rarity of the disease and the association, the available data regarding the sequence of management is controversial and is decided on a case by case basis. Case presentation a 55-year-old male with a history of uncontrolled hypertension, Chronic headaches, and kidney disease presented due to abrupt onset of crushing chest pain and was admitted for further evaluation of hypertensive emergency and NSTEMI with a blood pressure of 260/170 and Troponin of 3.8 ng/L. Coronary Angiography showed significant triple-vessel disease. Due to persistent hypertension and high suspicion of PCC, Serum metanephrine and normetanephrine, and fractioned catecholamines were ordered and showed significant elevation. CT of the abdomen and pelvis showed a 1.5 cm heterogeneous left adrenal mass. Nuclear medicine scan showed increased uptake of radiotracer in the left adrenal gland suggestive of PCC. Discussion PCC presents a high risk of morbidity and mortality, especially during surgical procedures if left untreated. The management of concomitant advanced CAD and PCC poses a unique challenge in terms of appropriate sequence and time interval between the two procedures. After a multidisciplinary team discussion including cardiology, cardiothoracic surgery, and endocrinology we decided to perform CABG first with preoperative preparation including Alpha-adrenoreceptor blockage for 1 week prior to surgery, followed by PCC resection at a later stage. The patient underwent coronary revascularization with grafting of three vessels. The perioperative course was uneventful. After three weeks the patient underwent successful PCC resection, with successful gradual down titration of alpha locate therapy. Conclusion A two-stage approach of CABG was PCC the section at a later stage under optimal preoperative preparation appears to be a safe and feasible modality in patients with advanced CAD and PCC. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.

Shank-localized cell wall growth contributes to Arabidopsis root hair elongation.

Root hairs are highly elongated tubular extensions of root epidermal cells with a plethora of physiological functions, particularly in establishing the root-rhizosphere interface. Anisotropic expansion of root hairs is generally thought to be exclusively mediated by tip growth-a highly controlled apically localized secretion of cell wall material-enriched vesicles that drives the extension of the apical dome. Here we show that tip growth is not the only mode of root hair elongation. We identified events of substantial shank-localized cell wall expansion along the polar growth axis of Arabidopsis root hairs using morphometric analysis with quantum dots. These regions expanded after in vivo immunolocalization using cell wall-directed antibodies and appeared as distinct bands that were devoid of cell wall labelling. Application of a novel click chemistry-enabled galactose analogue for pulse chase and real-time imaging allowed us to label xyloglucan, a major root hair glycan, and demonstrate its de novo deposition and enzymatic remodelling in these shank regions. Our data reveal a previously unknown aspect of root hair growth in which both tip- and shank-localized dynamic cell wall deposition and remodelling contribute to root hair elongation.

Cell wall ester modifications and volatile emission signatures of plant response to abiotic stress.

Growth suppression and defence signalling are simultaneous strategies that plants invoke to respond to abiotic stress. Here, we show that the drought stress response of poplar trees (Populus trichocarpa) is initiated by a suppression in cell wall derived methanol (MeOH) emissions and activation of acetic acid (AA) fermentation defences. Temperature sensitive emissions dominated by MeOH (AA/MeOH <30%) were observed from physiologically active leaves, branches, detached stems, leaf cell wall isolationsand whole ecosystems. In contrast, drought treatment resulted in a suppression of MeOH emissions and strong enhancement in AA emissions together with volatiles acetaldehyde, ethanol, and acetone. These drought-induced changes coincided with a reduction in stomatal conductance, photosynthesis, transpiration, and leaf water potential. The strong enhancement in AA/MeOH emission ratios during drought (400%-3500%) was associated with an increase in acetate content of whole leaf cell walls, which became significantly 13 C2 -labelled following the delivery of 13 C2 -acetate via the transpiration stream. The results are consistent with both enzymatic and nonenzymatic MeOH and AA production at high temperature in hydrated tissues associated with accelerated primary cell wall growth processes, which are downregulated during drought. While the metabolic source(s) require further investigation, the observations are consistent with drought-induced activation of aerobic fermentation driving high rates of foliar AA emissions and enhancements in leaf cell wall O-acetylation. We suggest that atmospheric AA/MeOH emission ratios could be useful as a highly sensitive signal in studies investigating environmental and biological factors influencing growth-defence trade-offs in plants and ecosystems.