Tim Brodribb

Tim Brodribb
University of Tasmania · School of Biological Science

PhD UTAS

About

218
Publications
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Publications

Publications (218)
Article
Full-text available
The fast and efficient recovery could be an important trait defining the efficacy of plant drought adaptation. In this work, we aimed to develop and set of simple and appropriate physiological proxies that could be used as reliable indicator to predict plant drought responses and validate the role of specific physiological traits such as root lengt...
Article
Plant transpiration is an inevitable consequence of photosynthesis and has a huge impact on the terrestrial carbon and water cycle, yet accurate and continuous monitoring of its dynamics is still challenging. Under well-watered conditions, canopy transpiration (Ec) could potentially be continuously calculated from stem water potential (Ψstem), but...
Article
Plant function arises from a complex network of structural and physiological traits. Explicit representation of these traits, as well as their connections with other biophysical processes, is required to advance our understanding of plant‐soil‐climate interactions. We used the Terrestrial Regional Ecosystem Exchange Simulator (TREES) to evaluate ph...
Article
Background and aims Hydraulic failure is considered a main cause of drought induced forest mortality. Yet, we have a limited understanding of how the varying intensities and long timescales of natural droughts induce and propagate embolism within the xylem. Methods X-ray computed tomography (microCT) images were obtained from different aged branch...
Article
Full-text available
One of the most prominent changes in neotropical forests has been the increase in abundance and size of lianas. Studies suggest that lianas have more acquisitive strategies than trees, which could allow them to take advantage of water more effectively when it is available in water-limited forests, but few studies compared across growth form (i.e.,...
Preprint
Full-text available
Plant function arises from a complex network of structural and physiological traits. Explicit representation of these traits, as well as their connections with other biophysical processes, is required to advance our understanding of plant-soil-climate interactions. We used the Terrestrial Regional Ecosystem Exchange Simulator (TREES) to evaluate ph...
Article
Forest mortality during drought has been attributed to hydraulic failure, which can be challenging to measure. A limited number of alternative proxies for incipient leaf death exist. Here we investigate whether a terminal increase in abscisic acid (ABA) levels in leaves occurs across vascular land plants and is an indicator of imminent leaf death....
Article
Full-text available
The hydraulic vulnerability segmentation (HVS) hypothesis implies the existence of differences in embolism resistance between plant organs along the xylem pathway and has been suggested as an adaptation allowing the differential preservation of more resource-rich tissues during drought stress. Compound leaves in trees are considered a low-cost mean...
Article
Vulnerability to xylem cavitation is a strong predictor of drought‐induced damage in forest communities. However, biotic features of the community itself can influence water availability at the individual tree‐level, thereby modifying patterns of drought damage. Using an experimental forest in Tasmania, Australia, we determined the vulnerability to...
Article
Background: Tip-to-base conduit widening is considered a key mechanism that enables vascular plants to grow tall by decreasing the hydraulic resistance imposed by increasing height. Widening of hydraulic anatomy (larger conducting elements towards the base of the vascular system) minimizes gradients in leaf-specific hydraulic conductance with plan...
Article
Damage to the plant water transport system through xylem cavitation is known to be a driver of plant death in drought conditions. However, a lack of techniques to continuously monitor xylem embolism in whole plants in vivo has hampered our ability to investigate both how this damage propagates, and the possible mechanistic link between xylem damage...
Article
Reproductive success largely defines the fitness of plant species. Understanding how heat and drought affect plant reproduction is thus key to predicting future plant fitness under rising global temperatures. Recent work suggests reproductive tissues are highly vulnerable to water stress in perennial plants where reproductive sacrifice could preser...
Article
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We introduce the AusTraits database - a compilation of values of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 448 traits across 28,640 taxa from field campaigns, published literature, taxonomic monographs, and individual taxon descriptions. Traits vary in scope from physiological measures of per...
Article
Aim Southern conifers have evolved under different evolutionary pressures compared with northern lineages, but in both regions these plants have undergone extensive extinction and range alteration over the Cenozoic (the last 66 Myr). It is not possible to observe the ecology of fossils directly, but indirect evidence of changes in bioclimatic envel...
Article
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The physiological mechanisms underlying drought responses are poorly documented in mangroves, which experience nearly constant exposure to saline water. We measured gas exchange, foliar abscisic acid (ABA) concentration, and vulnerability to embolism in a soil water-withholding experiment of two co-occurring mangroves, Avicennia marina (Forsskål) V...
Article
Root systems play a major role in supplying the canopy with water, enabling photosynthesis and growth. Yet, much of the dynamic response of root hydraulics and its influence on gas exchange during soil drying and recovery remains uncertain. We examined the decline and recovery of the whole root hydraulic conductance (Kr) and canopy conductance (gc...
Preprint
The mechanisms by which woody plants recover xylem hydraulic capacity after drought stress are not well understood, particularly with regard to the role of embolism refilling. We evaluated the recovery of xylem hydraulic capacity in young Eucalyptus saligna plants exposed to cycles of drought stress and rewatering. Plants were exposed to moderate a...
Preprint
Full-text available
We introduce the AusTraits database - a compilation of measurements of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 375 traits across 29230 taxa from field campaigns, published literature, taxonomic monographs, and individual taxa descriptions. Traits vary in scope from physiological measures of...
Article
Full-text available
20 Variation in resistance of xylem to embolism among flowers, leaves, and stems 21 strongly influences the survival and reproduction of plants. However, little is known 22 about the vulnerability to xylem embolism under drought stress and their 23 relationships to the anatomical traits of pits among reproductive and vegetative 24 organs. In this s...
Article
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Tight coordination in the photosynthetic, gas exchange and water supply capacities of leaves is a globally conserved trend across land plants. Strong selective constraints on leaf carbon gain create the opportunity to use quantitative optimization theory to understand the connected evolution of leaf photosynthesis and water relations. We developed...
Article
Full-text available
Root vulnerability to cavitation is challenging to measure and under-represented in current datasets. This gap limits the precision of models used to predict plant responses to drought because roots comprise the critical interface between plant and soil. In this study we measured vulnerability to drought induced cavitation in woody roots and stems...
Article
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Dynamic variation of the stomatal pore in response to changes in leaf-air vapour pressure difference (VPD) constitutes a critical regulation of daytime gas exchange. The stomatal response to VPD has been associated with both foliage abscisic acid (ABA) and leaf water potential (Ψ l ); however, causation remains a matter of debate. Here, we seek to...
Article
Photosynthetic efficiency of plants in different environments is controlled by stomata, hydraulics, biochemistry and mesophyll conductance (gm). Recently, gm was demonstrated as the key limitation of photosynthesis in gymnosperms. However, its values across gymnosperms varied over 20-fold, but this variation was poorly explained by robust structure...
Article
Full-text available
Trees are the living foundations on which most terrestrial biodiversity is built. Central to the success of trees are their woody bodies, which connect their elevated photosynthetic canopies with the essential belowground activities of water and nutrient acquisition. The slow construction of these carbon-dense, woody skeletons leads to a slow gener...
Article
Flowers underpin plant evolution, genetic legacy, and global food supply. They are exposed to similar evaporative conditions as leaves, yet floral physiology is a product of different selective forces. We used Tanacetum cinerariifolium, a perennial daisy, to examine the response of flowers to whole‐plant water stress, determining if flowers constit...
Article
Drought‐related tree mortality is now a widespread phenomenon predicted to increase in magnitude with climate change. However, the patterns of which species and trees are most vulnerable to drought, and the underlying mechanisms have remained elusive, in part due to the lack of relevant data and difficulty of predicting the location of catastrophic...
Article
The size of plant stomata (adjustable pores that determine the uptake of CO 2 and loss of water from leaves) is considered to be evolutionarily important. This study uses fossils from the major Southern Hemisphere family Proteaceae to test whether stomatal cell size responded to Cenozoic climate change. We measured the length and abundance of guard...
Article
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The hydraulic implications of stomatal positioning across leaf surfaces and the impact on internal water flow through amphistomatic leaves are not currently well understood. Amphistomaty potentially provides hydraulic efficiencies if the majority of hydraulic resistance in the leaf exists outside the xylem in the mesophyll. Such a scenario would me...
Article
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1.Recent findings suggest that tree mortality and post‐drought recovery of gas exchange can be predicted from loss of function within the water transport system. Understanding the susceptibility of plants to hydraulic damage requires knowledge about the vulnerability of different plant organs to stress‐induced hydraulic dysfunction. This is particu...
Article
The best predictor of leaf level photosynthetic rate is the porosity of the leaf surface, as determined by the number and aperture of stomata on the leaf (Wong et al. 1979; Franks and Beerling 2009; Boyer 1976). This remarkable correlation between stomatal porosity (or diffusive conductance to water vapour‐ gs) and CO2 assimilation rate (A) applies...
Article
Recent research on evolutionarily old species has uncovered mesophyll conductance (gm) as a key player in realized assimilation, but considerable variation was found. However, in gymnosperms, photosynthetic limitations, particularly how limitation combinations contribute to realized photosynthetic rates, have been studied in very few species preclu...
Article
Our power to predict the future relies on our knowledge of the past. Paleoproxies are a powerful tool for understanding environmental and ecological conditions and changes across different time periods. However, constructing a functioning paleoproxy requires a well-constrained and robustly tested model. This is challenging, especially if ecological...
Article
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The vulnerability of forest species and tree populations to climate change is related to the exposure of the ecosystem to extreme climatic conditions and to the adaptive capacity of the population to cope with those conditions. Adaptive capacity is a relatively under-researched topic within the forest science community and there is an urgent need t...
Article
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Tree mortality during hot and dry conditions presents a stark reminder of the vulnerability of plant species to climatic extremes. The current global warming trend makes predicting the impacts of hot/dry events on species survival an urgent task; yet, the standard tools for this purpose lack a physiological basis. This review examines a diversity o...
Article
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Key message Comparing juvenile and adult shoots of Eucalyptus globulus reveals that juvenile leaves are more vulnerable to hydraulic failure than adults while stems show no significant differences. Abstract Understanding variation in the susceptibility for xylem tissue to cavitate and lose its function during water stress exposure is critical for...
Article
Full-text available
Photosynthesis in bryophytes and lycophytes has received less attention than terrestrial plant groups. In particular, few studies have addressed the non‐stomatal diffusion conductance to CO2 (gnsd) of these plant groups. Their lower photosynthetic rate per leaf mass area at any given nitrogen concentration as compared to vascular plants suggested a...
Article
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Drought stress is a major limiting factor for crop production in the arid and semi‐arid regions. Here, we screened eighty barley (Hordeum vulgare L.) genotypes collected from different geographical locations contrasting in drought stress tolerance and quantified a range of physiological and agronomical indices in glasshouse trails. The experiment w...
Article
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Key message Direct, non-invasive X-ray microtomography and optical technique observations applied in stems and leaves of intact seedlings revealed that laurel is highly resistant to drought-induced xylem embolism. Contrary to what has been brought forward, daily cycles of embolism formation and refilling are unlikely to occur in this species and to...
Article
Drought stress can result in significant impairment of the plant hydraulic system via blockage of xylem conduits by gas emboli. Recovery after drought stress is an essential component of plant survival but is still a poorly understood process. In this study, we examined the capacity of woody species from two genera (Eucalyptus and Quercus) to refil...
Article
The ability to resist hydraulic dysfunction in leaves, stems and roots strongly influences whether plants survive and recover from drought. However, the coordination of hydraulic function among different organs within species and their links to gas exchange during drought and recovery remains understudied. Here we examine the interaction between ga...
Article
Full-text available
New techniques now make it possible to precisely and accurately determine the failure threshold of the plant vascular system during water stress. This creates an opportunity to understand the vulnerability of species to drought, but first it must be determined whether damage to leaf function associated with xylem cavitation is reparable or permanen...
Article
Severe droughts have caused widespread tree mortality across many forest biomes with profound effects on the function of ecosystems and carbon balance. Climate change is expected to intensify regional-scale droughts, focusing attention on the physiological basis of drought-induced tree mortality. Recent work has shown that catastrophic failure of t...
Article
Water availability has frequently been linked to seasonal leaf display in seasonally dry ecosystems, but there have been few ecohydrological investigations of this link. Miombo woodland is a dominant seasonally dry tropical forest ecosystem type in southern Africa; however, there are few data on the relationship between seasonal dynamics in plant-w...
Article
Investment in leaf veins (supplying xylem water) is balanced by stomatal abundance, such that sufficient water transport is provided for stomata to remain open when soil water is abundant. This coordination is mediated by a common dependence of vein and stomatal densities on cell size. Flowers may not conform to this same developmental pattern if t...
Article
Full-text available
The capacity of plant species to resist xylem cavitation is an important determinant of resistance to drought, mortality thresholds, geographic distribution and productivity. Unravelling the role of xylem cavitation vulnerability in plant evolution and adaptation requires a clear understanding of how this key trait varies between the tissues of ind...
Article
Full-text available
Rapid biosynthesis of abscisic acid (ABA) in the leaf, triggered by a decrease in cell volume, is essential for a functional stomatal response to vapour pressure deficit (VPD) in angiosperms. However, it is not known whether rapid biosynthesis of ABA is triggered in other plant tissues as well. Through the application of external pressure to flower...
Chapter
In most terrestrial ecosystems, water availability is the principal governor of primary productivity. Vascular plants can only sustain high rates of photosynthetic activity by transporting enormous quantities of water from reserves in the soil to the sites of gas exchange in leaves to prevent desiccation of photosynthetic tissues. This demand for w...
Article
Full-text available
Understanding intraspecific variation in the vulnerability of the xylem to hydraulic failure during drought is critical in predicting the response of forest tree species to climate change. However, few studies have assessed intraspecific variation in this trait, and a likely limitation is the large number of measurements required to generate the st...
Article
Full-text available
Producing leaves with closely spaced veins is a key innovation linked to high rates of photo-synthesis in angiosperms. A close geometric link between veins and stomata in angio-sperms ensures that investment in enhanced venous water transport provides the strongest net carbon return to the plant. This link is underpinned by " passive dilution " via...
Data
Table of data used for analyses. (XLSX)
Article
Full-text available
Land plants lose vast quantities of water to the atmosphere during photosynthetic gas exchange. In angiosperms a complex network of veins irrigates the leaf, and it is widely held that the density and placement of these veins determines maximum leaf hydraulic capacity and thus maximum photosynthetic rate. This theory is largely based on interspecif...
Article
Homologs of the Arabidopsis core abscisic acid (ABA) signalling component OPEN STOMATA1 (OST1) are best known for their role in closing stomata in angiosperm species. We recently characterised a fern OST1 homolog, GAMETOPHYTES ABA INSENSITIVE ON ANTHERDIOGEN 1 (GAIA1), which is not required for stomatal closure in ferns, consistent with physiologic...
Article
Full-text available
Widespread tree mortality associated with drought has been observed on all forested continents and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere-atmosphere interactions of carbon, water and energy balance, and is poorly represented in dynamic vegetation models. Reducing unce...
Article
Full-text available
The vulnerability of plant water transport tissues to a loss of function by cavitation during water stress is a key indicator of the survival capabilities of plant species during drought. Quantifying this important metric has been greatly advanced by non-invasive techniques that allow embolisms to be directly viewed in the vascular system. Here we...
Article
The occurrence of amphistomatic leaves (stomata on both surfaces) versus hypostomatic leaves (stomata limited to the lower or abaxial surface) has strong associations with environment. Amphistomy provides the advantage of higher conductance of CO2 for photosynthesis, however, unless the stomata on both leaf surfaces can be independently controlled...
Article
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Background While most water loss from leaf surfaces occurs via stomata, part of this loss also occurs through the leaf cuticle, even when the stomata are fully closed. This component, termed residual transpiration, dominates during the night and also becomes critical under stress conditions such as drought or salinity. Reducing residual transpirati...
Article
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Drought can cause major damage to plant communities, but species damage thresholds and postdrought recovery of forest productivity are not yet predictable. We used an El Niño drought event as a natural experiment to test whether postdrought recovery of gas exchange could be predicted by properties of the water transport system, or if metabolism, pr...
Article
Full-text available
Water stress is known to cause xylem cavitation in the leaves, roots and stems of plants, but little is known about the vulnerability of flowers to xylem damage during drought. This is an important gap in our understanding of how and when plants become damaged by water stress. Here we address fundamental questions about if and when flowers suffer c...