Biology subjects

Gleason, S. M.

Publications and source records attributed to Gleason, S. M..

5 recordsLinked to original sources

bioRxiv2026

Beyond air-seeding: Dynamic, multiphase interactionsreveal a two-step mechanism of embolism propagation inangiosperm xylem

BackgroundThe mechanism underlying drought-induced embolism in angiosperm xylem has been attributed to air-seeding. This concept describes the bulk flow of gas from embolised to neighbouring conduits through the penetration of gas-liquid menisci across pores in interconduit pit membranes. While there is compelling evidence for the spatial propagation of embolism, air-seeding rests on various simplifying assumptions. Among others, air-seeding presumes that xylem sap has physical properties comparable to pure water, that pit membranes can be approximated as structures with simple pores, and that embolism occurs whenever a gas-liquid interface crosses a pit membrane. ScopeRecent experimental and theoretical work demonstrates that the biophysical conditions and processes governing gas-liquid interactions at interconduit pit membranes are fundamentally more dynamic and complex than assumed by air-seeding. These phenomena include: (1) gas movement through constriction pore networks, (2) insoluble, polar lipids at conduit surfaces and interfaces, (3) dynamic surface tension of xylem sap that depends on the local packing density of interfacial lipids, (4) bubble snap-off dynamics within pit membranes, (5) surfactant-stabilized nanobubbles in sap that is oversaturated with dissolved gas, and (6) electrostatic interactions between charged interfaces. Importantly, embolism propagation involves bubble generation and embolism formation as distinct, temporarily and spatially separated processes. Embolism formation occurs when nanobubbles become unstable, whereas nanobubbles below critical stability thresholds can remain stable in sap-filled conduits. ConclusionsTogether, these findings reconfirm that pit membranes function as safety valves enabling water transport according to the cohesion-tension theory, and provide mechanistic insights into embolism propagation. They address the question why plants do not suffer constant embolism formation despite negative xylem pressures. We conclude that a revised framework explicitly accounting for the 3D structure of pit membranes, and multiphase, dynamic processes operating within them are required to explain the biophysics underlying water transport and embolism resistance in angiosperm xylem.

plant biology↗

bioRxiv2024

A test of limited transpiration traits in sorghum to improve late-season water use, photosynthesis, growth, and grain yield in the high plains of Northern Colorado

Limited transpiration (LT) traits aim to conserve early-season water to benefit late-season grain development. While theoretical and modeling efforts support LT efficacy, empirical tests directly measuring water loss from leaves and canopies are scarce. This study evaluates the performance of LT genotypes in achieving reduced early-season water use and improved late-season growth and yield in semi-arid Colorado. The research involved near-isogenic lines (NILs) derived from sorghum inbred lines, subjected to different irrigation treatments. Measurements included stomatal conductance, net CO2 assimilation, and photosystem II (PSII) efficiency. Results indicate that LT genotypes did not consistently exhibit lower early-season water use or higher late-season growth compared to non-LT genotypes. Early-season water use was positively correlated with above-ground biomass, challenging the assumption that early-season water conservation can be leveraged for late-season benefits. We question the efficacy of LT traits, highlighting the physiological link between water use and carbon gain, and the potential opportunity costs of reduced early-season growth. We suggests that breeding strategies should focus on enhancing deep soil water access and maximizing carbon gain rather than merely reducing transpiration or shifting water use in arid and semi-arid environments.

plant biology↗

bioRxiv2022

Physiological trait networks enhance understanding of crop growth and water use in contrasting environments

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 physiological trait networks in maize. Net primary productivity (NPP) and grain yield were simulated across five contrasting climate scenarios. Simulations achieving high NPP and grain yield in high precipitation environments featured trait networks conferring high water use strategies: deep roots, high stomatal conductance at low water potential ("risky" stomatal regulation), high xylem hydraulic conductivity, and high maximal leaf area index. In contrast, high NPP and grain yield was achieved in dry environments with low late-season precipitation via water conserving trait networks: deep roots, high embolism resistance, and low stomatal conductance at low leaf water potential ("conservative" stomatal regulation). We suggest that our approach, which allows for the simultaneous evaluation of physiological traits and their interactions (i.e., networks), has potential to improve crop growth predictions in different environments. In contrast, evaluating single traits in isolation of other coordinated traits does not appear to be an effective strategy for predicting plant performance. Summary statementOur process-based model uncovered two beneficial but contrasting trait networks for maize which can be understood by their integrated effect on water use/conservation. Modification of multiple, physiologically aligned, traits were required to bring about meaningful improvements in NPP and yield.

plant biology↗

bioRxiv2021

Growth and grain yield of eight maize hybrids is aligned with water transport, stomatal conductance, and photosynthesis in a semi-arid irrigated system

There is increasing interest in understanding how trait networks can be manipulated to improve the performance of crop species. Working towards this goal, we have identified key traits linking the acquisition of water, the transport of water to the sites of evaporation and photosynthesis, stomatal conductance, and growth across eight maize hybrid lines grown under well-watered and water-limiting conditions in Northern Colorado. Under well-watered conditions, well-performing hybrids exhibited high leaf-specific conductance, low operating water potentials, high rates of midday stomatal conductance, high rates of net CO2 assimilation, greater leaf osmotic adjustment, and higher end-of-season growth and grain yield. This trait network was similar under water-limited conditions with the notable exception that linkages between water transport, midday stomatal conductance, and growth were even stronger than under fully-watered conditions. The results of this experiment suggest that similar trait networks might confer improved performance under contrasting climate and soil conditions, and that efforts to improve the performance of crop species could possibly benefit by considering the water transport pathway within leaves, as well as within the whole-xylem, in addition to root-level and leaf-level traits.

plant biology↗

bioRxiv2019

Wood capacitance is related to water content, wood density, and anatomy across 30 temperate tree species

Water released from wood tissue during transpiration (capacitance) can meaningfully affect daily water use and drought response. To provide context for better understanding of capacitance mechanisms, we investigated links between capacitance and wood anatomy. On twig wood of 30 temperate angiosperm tree species, we measured capacitance, water content, wood density, and anatomical traits, i.e., vessel dimensions, tissue fractions, and vessel-tissue contact fractions (fraction of vessel circumference in contact with other tissues). Across all species, the strongest predictors of capacitance were wood density (WD) and predawn lumen volumetric water content (VWCL-pd, r2adj=0.44, P<0.0001). Vessel-tissue contact fractions explained an additional [~]10% of the variation in capacitance. Regression models were not improved by including predawn relative water content (RWCpd) or tissue lumen fractions. Among diffuse-porous species, VWCL-pd and vessel-ray contact fraction were the best predictors of capacitance, whereas among ring/semi-ring-porous species, VWCL-pd, WD and vessel-fibre contact fraction were the best predictors. Mean RWCpd was 0.65{+/-}0.13 and uncorrelated with WD. VWCL-pd was weakly negatively correlated with WD. Our findings imply that capacitance depends on the amount of stored water, tissue connectivity and the bulk wood properties arising from WD (e.g., elasticity), rather than the fraction of any particular tissue.

plant biology↗