Search NASA⌕ Search

SEARCH · Search NASA

Results for “root plasticity”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Root architectural plasticity optimizes nutrient acquisition in switchgrass under variable phosphorus forms

Aims Understanding the influence of different forms of phosphorus (P) over the different root traits and how those traits are related to increasing the efficiency of nutrient acquisition strategies. Methods Investigation of switchgrass (Panicum virgatum L.) root morphology responses to inorganic P (Pi) soluble (Potassium-P), insoluble (Aluminum-P), and organic P (Po) (Inositol Hexa-Phosphate, IHex-P) in rhizoboxes. Roots were traced over the root box and scanned using WinRhizoTM. The CRootbox model was employed to simulate root growth. Results Significant plasticity observed under IHex-P treatment, with a 46% increase in root branching, leading to a 74% rise in total root length and a 65% increase in root surface area compared to inorganic P forms. IHex-P resulted in a 73% higher root biomass than Aluminum-P and a 26% increase compared to Potassium-P. Most of the differences were attributed to the elongation of root branches. Conclusions Here, the study emphasizes the dynamic nature of switchgrass root architecture and morphology in response to varying P forms in the soil. The absence of Pi in the soil triggered increased plasticity in root traits, facilitating root access to Po and uptake of P. These findings offer valuable insights into the adaptive mechanisms of perennial plants, with significant implications for optimizing nutrient acquisition strategies in both agricultural and natural ecosystems.

Organic phosphorus↗
NASA NTRS2016

Chapter 7: Fluorescence Imaging of the Cytoskeleton in Plant Roots

During the past two decades the use of live cytoskeletal probes has increased dramatically due to the introduction of the green fluorescent protein. However, to make full use of these live cell reporters it is necessary to implement simple methods to maintain plant specimens in optimal growing conditions during imaging. To image the cytoskeleton in living Arabidopsis roots, we rely on a system involving coverslips coated with nutrient supplemented agar where the seeds are directly germinated. This coverslip system can be conveniently transferred to the stage of a confocal microscope with minimal disturbance to the growth of the seedling. For roots with a larger diameter such as Medicago truncatula, seeds are first germinated in moist paper, grown vertically in between plastic trays, and roots mounted on glass slides for confocal imaging. Parallel with our live cell imaging approaches, we routinely process fixed plant material via indirect immunofluorescence. For these methods we typically use non-embedded vibratome-sectioned and whole mount permeabilized root tissue. The clearly defined developmental regions of the root provide us with an elegant system to further understand the cytoskeletal basis of plant development.

Actin↗
NASA NTRS1974

An approximate method of analysis for notched unidirectional composites

An approximate method is proposed for the analysis of unidirectional, filamentary composite materials having slit notches perpendicular to the fibers and subjected to tension parallel to the fibers. The approach is based on an engineering model which incorporates important effects of material heterogeneity by considering average extensional stresses in the fibers and average shear stresses in the matrix. Effects of interfacial failure and matrix plasticity at the root of the notch are considered. Predictions of the analysis are in reasonably good agreement with previous analytical models and experimental data for graphite/epoxy.

Zweben, C.↗
DOE OSTI2025

Uptake of polystyrene nanospheres by wheat and Arabidopsis roots in agar, hydroponics, and soil

Plant uptake of micro- and nanoplastics can lead to contamination of food with plastic particles and subsequent human consumption of plastics. There is evidence that plant roots can take up micro and nanoplastics; however, most of this evidence stems from experiments conducted with plants grown in hydroponics or agar systems where uptake of nanoparticles by roots is more favorable than when plants were grown in soil. Here, we discern the root uptake and accumulation of polystyrene nanospheres in plants grown in different growth media: agar, hydroponics, and soil. In addition, we tested the impacts of nanospheres on plant biomass and plant stress. Wheat and Arabidopsis thaliana were grown in agar, hydroponics, and soil media and exposed to polystyrene nanospheres. Three different nanospheres were used (40 nm and 200 nm carboxylate-modified and 200 nm amino-modified polystyrene) and uniformly mixed into the growth media. Plants were grown for 7 to 10 days and the roots were then examined for the presence of nanospheres by confocal laser scanning microscopy and scanning electron microscopy. Plant stress was evaluated by measuring reactive oxygen species (ROS). We observed the 40 nm nanospheres inside the plant roots, but the 200 nm nanospheres only adhered to the root cap cells showing no uptake into the roots. Furthermore, confocal images indicated that root uptake of nanospheres was favored in hydroponic solutions as compared to agar and soil media. Plant biomass was generally not affected by the nanospheres, except for hydroponically grown Arabidopsis thaliana, where biomass was significantly reduced. Small sized (40 nm) and positively charged (200 nm amino-modified) nanospheres showed higher ROS accumulation in plants than negatively charged 200 nm carboxylate-modified nanospheres. In conclusion, this study provides evidence that polystyrene nanospheres can be taken up into the interior of plant roots and cause plant stress, but these impacts are less pronounced in media where the plastic particles are less mobile, like in agar and soil media as compared to hydroponic systems.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2003

Development of a Fatigue Crack Growth Coupon for Highly Plastic Stress Conditions

The analytical approach used to develop a novel fatigue crack growth coupon for highly plastic stress field condition is presented in this paper. The flight hardware investigated is a large separation bolt that has a deep notch, which produces a large plastic zone at the notch root when highly loaded. Four test specimen configurations are analyzed in an attempt to match the elastic-plastic stress field and crack constraint conditions present in the separation bolt. Elastic-plastic finite element analysis is used to compare the stress fields and critical fracture parameters. Of the four test specimens analyzed, the modified double-edge notch tension - 3 (MDENT-3) most closely approximates the stress field, J values, and crack constraint conditions found in the flight hardware. The MDENT-3 is also most insensitive to load misalignment and/or load redistribution during crack growth.

Allen, Phillip A.↗
NASA NTRS1983

Benchmark cyclic plastic notch strain measurements

Plastic strains at the roots of notched specimens of Inconel 718 subjected to tension-compression cycling at 650 C are reported. These strains were measured with a laser-based technique over a gage length of 0.1 mm and are intended to serve as 'benchmark' data for further development of experimental, analytical, and computational approaches. The specimens were 250 mm by 2.5 mm in the test section with double notches of 4.9 mm radius subjected to axial loading sufficient to cause yielding at the notch root on the tensile portion of the first cycle. The tests were run for 1000 cycles at 10 cpm or until cracks initiated at the notch root. The experimental techniques are described, and then representative data for the various load spectra are presented. All the data for each cycle of every test are available on floppy disks from NASA.

Sharpe, W. N., Jr.↗
NASA NTRS1991

Capillary-Effect Root-Environment System

Capillary-effect root-environment system (CERES) is experimental apparatus for growing plants in nutrient solutions. Solution circulated at slight tension in cavity filled with plastic screen and covered by porous plastic membrane. By adsorptive attraction, root draws solution through membrane. Conceived for use in microgravity of space, also finds terrestrial application in germinating seedlings, because it protects them from extremes of temperature, moisture, and soil pH and from overexposure to fertilizers and herbicides.

Wright, Bruce D.↗
NASA NTRS1985

A hydroponic method for plant growth in microgravity

A hydroponic apparatus under development for long-term microgravity plant growth is described. The capillary effect root environment system (CERES) is designed to keep separate the nutrient and air flows, although both must be simultaneously available to the roots. Water at a pressure slightly under air pressure is allowed to seep into a plastic depression covered by a plastic screen and a porous membrane. A root in the air on the membrane outer surface draws the moisture through it. The laboratory model has a wire-based 1.241 mm mesh polyethylene screen and a filter membrane with 0.45 micron pores, small enough to prohibit root hair penetration. The design eliminates the need to seal-off the plant environment. Problems still needing attention include scaling up of the CERES size, controlling biofouling of the membrane, and extending the applications to plants without fibrous root systems.

Wright, B. D.↗
NASA NTRS2015

Effect of Notches on Creep-Fatigue Behavior of a P/M Nickel-Based Superalloy

A study was performed to determine and model the effect of high temperature dwells on notched low cycle fatigue (NLCF) and notch stress rupture behavior of a fine grain LSHR powder metallurgy (PM) nickel-based superalloy. It was shown that a 90 second dwell applied at the minimum stress (min dwell) was considerably more detrimental to the NLCF lives than similar dwell applied at the maximum stress (max dwell). The short min dwell NLCF lives were shown to be caused by growth of small oxide blisters which caused preferential cracking when coupled with high concentrated notch root stresses. The cyclic max dwell notch tests failed mostly by a creep accumulation, not by fatigue, with the crack origin shifting internally to a substantial distance away from the notch root. The classical von Mises plastic flow model was unable to match the experimental results while the hydrostatic stress profile generated using the Drucker-Prager plasticity flow model was consistent with the experimental findings. The max dwell NLCF and notch stress rupture tests exhibited substantial creep notch strengthening. The triaxial Bridgman effective stress parameter was able to account for the notch strengthening by collapsing the notched and uniform gage geometry test data into a singular grouping.

Dwell Notch Fatigue↗
NASA NTRS1985

A comparison of smooth specimen and analytical simulation techniques for notched members at elevated temperatures

Experimental strain measurements have been made at the highly strained regions on notched plate specimens that were made of Hastelloy X. Tests were performed at temperatures up to 1,600 F. Variable load patterns were chosen so as to produce plastic and creep strains. Were appropriate, notch root stresses were experimentally estimated by subjecting a smooth specimen to the measured notch root strains. The results of three analysis techniques are presented and compared to the experimental data. The most accurate results were obtained from an analysis procedure that used a smooth specimen and the Neuber relation to simulate the notch root stress-strain response. When a generalized constitutive relation was used with the Neuber relation, good results were also obtained, however, these results were not as accurate as those obtained when the smooth specimen was used directly. Finally, a general finite element program, ANYSIS, was used which resulted in acceptable solutions, but, these were the least accurate predictions.

Martin, J. F.↗
NASA NTRS1994

On the measurement of the crack tip stress field as a means of determining Delta K(sub eff) under conditions of fatigue crack closure

The optical method of caustics has been successfully extended to enable stress intensity factors as low as 1MPa square root of m to be determined accurately for central fatigue cracks in 2024-T3 aluminium alloy test panels. The feasibility of using this technique to study crack closure, and to determine the effective stress intensity factor range, Delta K(sub eff), has been investigated. Comparisons have been made between the measured values of stress intensity factor, K(sub caus), and corresponding theoretical values, K(sub theo), for a range of fatigue cracks grown under different loading conditions. The values of K(sub caus) and K(sub theo) were in good agreement at maximum stress, where the cracks are fully open, while K(sub caus) exceeded K(sub theo) at minimum stress, due to crack closure. However, the levels of crack closure and values of Delta K(sub eff) obtained could not account for the variations of crack growth rate with loading conditions. It is concluded that the values of Delta K(sub eff), based on caustic measurements in a 1/square root of r stress field well outside the plastic zone, do not fully reflect local conditions which control crack tip behavior.

Wallhead, Ian R.↗
NASA NTRS2012

Dwell Notch Low Cycle Fatigue Behavior of a Powder Metallurgy Nickel Disk Alloy

A study was conducted to determine the processes which govern dwell notch low cycle fatigue (NLCF) behavior of a powder metallurgy (P/M) ME3 disk superalloy. The emphasis was placed on the environmentally driven mechanisms which may embrittle the highly stressed notch surface regions and reduce NLCF life. In conjunction with the environmentally driven notch surface degradation processes, the visco-plastic driven mechanisms which can significantly change the notch root stresses were also considered. Dwell notch low cycle fatigue testing was performed in air and vacuum on a ME3 P/M disk alloy specimens heat treated using either a fast or a slow cooling rate from the solutioning treatment. It was shown that dwells at the minimum stress typically produced a greater life debit than the dwells applied at the maximum stress, especially for the slow cooled heat treatment. Two different environmentally driven failure mechanisms were identified as the root cause of early crack initiation in the min dwell tests. Both of these failure mechanisms produced mostly a transgranular crack initiation failure mode and yet still resulted in low NLCF fatigue lives. The lack of stress relaxation during the min dwell tests produced higher notch root stresses which caused early crack initiation and premature failure when combined with the environmentally driven surface degradation mechanisms. The importance of environmental degradation mechanisms was further highlighted by vacuum dwell NLCF tests which resulted in considerably longer NLCF lives, especially for the min dwell tests.

Telesman, J.↗
DOE OSTI2026

Polymer Deconstruction and Redesign Strategies for Plastics Recycling

Advancing plastics recycling requires both the selective deconstruction of existing polymers and the design of new materials that enable efficient reuse without loss of performance. This perspective highlights an integrated approach that is rooted in polymer chemistry, catalysis, and process engineering which can enable a circular plastics economy. Here, we outline recent advances in catalytic, solvolytic, and enzymatic pathways for plastic deconstruction, and examine the molecular design principles driving next-generation recyclable-by-design and bio-based polymers. Despite these advances, major knowledge gaps remain in understanding the evolution of polymer morphology and catalyst structure during deconstruction, assessing deconstruction processes with realistic polymers, and offering redesigned polymers with competitive cost and environmental advantage over conventional plastics. United States Department of Energy (U.S. DOE) national laboratories offer unique capabilities to address these challenges through in situ and operando characterization, high-throughput experimentation, environmental studies, technoeconomic and life cycle assessment, scale-up support, and collaboration networks. Advances made in understanding plastic deconstruction mechanisms and structure-property correlations of redesigned polymers inform emerging research directions including autonomous experimentation, real-time feedback-enabled process optimization, and protein engineering for enzymatic depolymerization.

36 MATERIALS SCIENCE↗
NASA NTRS1986

Experimental evaluation criteria for constitutive models of time dependent cyclic plasticity

Notched members were tested at temperatures far above those recorded till now. Simulation of the notch root stress response was accomplished to establish notch stress-strain behavior. Cyclic stress-strain profiles across the net-section were recorded and on-line direct notch strain control was accomplished. Data are compared to three analysis techniques with good results. The objective of the study is to generate experimental data that can be used to evaluate the accuracy of constitutive models of time dependent cyclic plasticity.

Martin, J. F.↗