Search NASA⌕ Search

SEARCH · Search NASA

Results for “LEAVES”

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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Expansion and photosynthetic rate of leaves of soybean plants during onset of and recovery from nitrogen stress

This study reports on the effects of nitrogen stress and restoration of nitrogen availability after a period of stress on expansion and photosynthetic rate of soybean leaves of differing maturity. We hypothesized that nitrogen resupply would lead to additional accumulation of reduced nitrogen in the leaves and, ultimately, resumption of leaf initiation and expansion and photosynthetic activity. In continuously nitrogen-stressed plants, expansion of middle trifoliolates of main-stem trifoliates and leaf area at full expansion were severely restricted. Leaves showing the greatest effects were initiated after removal of nitrogen. When the reduced nitrogen concentration in mature leaves of continuously stressed plants fell below 9 mg dm-2, the photosynthetic rate per unit leaf decreased rapidly, reaching a minimum of ca. 6-8 mg dm-2 h-1. The older mature leaves tended to abscise at this point, while the youngest leaves remained on the plant and continued to photosynthesize slowly. When nitrogen was resupplied, leaf expansion and final leaf area increased. Leaf initiation was also stimulated as reduced nitrogen levels rose in the leaves. Photosynthetic rates of the oldest and youngest pair of mature leaves returned to values comparable to those of similar-aged leaves of nonstressed soybean plants.

NASA Discipline Number 61-10↗
DOE OSTI2016

Autophagy induction in tobacco leaves infected by potato virus Y{sup O} and its putative roles

Autophagy plays a critical role in the innate immune response of plants to pathogen infection. In the present study, we examined autophagy induced by potato virus Y ordinary strain (PVY{sup O}) infection in tobacco (Nicotiana benthamiana). Enzyme-linked immunosorbent assays revealed that the number of virus particles in the plant peaked at 2 weeks post-inoculation and then gradually decreased. Additionally, the amount of virus increased significantly in the 3rd and 4th leaves distal to the inoculated leaf and decreased slightly in the 5th leaf. Within 2 weeks of PVY{sup O} inoculation, the tobacco leaves showed typical symptoms of Potyvirus inoculation, including mottling, yellowing, a mosaic pattern, and necrotic tissue changes at the inoculated site. Based on an ultrastructural analysis of the PVY{sup O}-infected tobacco leaves, virus aggregates appeared as longitudinal and transverse arrays and pinwheels, which are typical of Potyvirus inoculation. Moreover, PVY{sup O} infection caused changes in the number, size, and shape of chloroplasts, whereas the number of plastogranules increased markedly. Furthermore, double-membrane autophagosome-like vacuoles, including electron-dense materials, laminated structures, and cellular organelles, were found. The induction of autophagy after the PVY{sup O} infection of tobacco leaves was further confirmed by the expression of lipidated microtubule-associated protein 1 light chain 3 (LC3)-II, an autophagy marker and p62, an autophagy adaptor protein. The LC3-II levels increased daily over the 4-week period. Although virus inoculation was performed systemically on the basal leaves of the plants, LC3-II was expressed throughout the leaves and the expression was higher in leaves distal to the inoculated leaf. Moreover, PVY{sup O} infection caused the activation of stress-activated protein kinases/c-Jun N-terminal kinases. Therefore, PVY{sup O} infection-induced autophagy was positively correlated with the virus content, suggesting that autophagy induction following PVY{sup O} infection is involved in the anti-pathogen response of the host. -- Highlights: •The amount of PVY{sup O} revealed a peak at 2 weeks post-inoculation. •The amount of PVY{sup O} was higher in leaves distal to the inoculated leaf. •PVY{sup O} infection produced typical PVY infection symptoms. •Double-membranous vacuoles, including cellular organelles, were induced by PVY{sup O} infection. •PVY{sup O} infection induced LC3-II and JNK activation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Prioritization of copper for the use in photosynthetic electron transport in developing leaves of hybrid poplar

Plastocyanin (PC) is an essential and abundant copper (Cu) protein required for photosynthesis in higher plants. Severe copper deprivation has the potential to cause a defect in photosynthetic electron transport due to a lack in PC. The Cu-microRNAs, which are up-regulated under Cu deficiency, down-regulate the expression of target Cu proteins other than PC, cytochrome-c oxidase and the ethylene receptors. It has been proposed that this mechanism saves Cu for PC maturation. We aimed to test how hybrid poplar, a species that has capacity to rapidly expand its photosynthetically active tissue, responds to variations in Cu availability over time. Measurement of chlorophyll fluorescence after Cu depletion revealed a drastic effect on photosynthesis in hybrid poplar. The decrease in photosynthetic capacity was correlated with a reduction in PC protein levels. Compared to older leaves, PC decreased more strongly in developing leaves, which also lost more photosynthetic electron transport capacity. The effect of Cu depletion on older and more developed leaves was minor and these leaves maintained much of their photosynthetic capacity. Interestingly, upon resupply of Cu to the medium a very rapid recovery of Cu levels was seen in the younger leaves with a concomitant rise in the expression and activity of PC. In contrast, the expression of those Cu proteins, which are targets of microRNAs was under the same circumstances delayed. At the same time, Cu resupply had only minor effects on the older leaves. The data suggest a model where rapid recovery of photosynthetic capacity in younger leaves is made possible by a preferred allocation of Cu to PC in younger leaves, which is supported by Cu-microRNA expression.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1973

Spectra of normal and nutrient-deficient maize leaves

Reflectance, transmittance and absorptance spectra of normal and six types of nutrient-deficient (N, P, K, S, Mg, and Ca) maize (Zea mays L.) leaves were analyzed at 30 selected wavelengths from 500 to 2600 nm. The analysis of variance showed significant differences in reflectance, transmittance and absorptance in the visible wavelengths among leaf numbers 3, 4, and 5, among the seven treatments, and among the interactions of leaf number and treatments. In the infrared wavelengths only treatments produced significant differences. The chlorophyll content of leaves was reduced in all nutrient-deficient treatments. Percent moisture was increased in S-, Mg-, and N-deficiencies. Polynomial regression analysis of leaf thickness and leaf moisture content showed that these two variables were significantly and directly related. Leaves from the P- and Ca-deficient plants absorbed less energy in the near infrared than the normal plants; S-, Mg-, K-, and N-deficient leaves absorbed more than the normal. Both S- and N-deficient leaves had higher temperatues than normal maize leaves.

Al-Abbas, A. H.↗
NASA NTRS1975

Differences in visible and near-infrared light reflectance between orange fruit and leaves

The objective was to find the best time during the season (April 26, 1972 to January 8, 1973) to distinguish orange fruit from leaves by spectrophotometrically determining at 10-day intervals when the difference in visible (550- and 650-nm wavelengths) and near-infrared (850-nm wavelength) light reflectance between fruit and nearby leaves was largest. December 5 to January 8 was the best time to distinguish fruit from leaves. During this period the fruit's color was rapidly changing from green to yellow, and the difference in visible light reflectance between fruit and leaves was largest. The difference in near-infrared reflectance between leaves and fruit remained essentially constant during ripening when the difference in visible light reflectance between leaves and fruit was largest.

Gausman, H. W.↗
NASA NTRS1990

Light-stimulated cell expansion in bean (Phaseolus vulgaris L.) leaves. I. Growth can occur without photosynthesis

Cell expansion in dicotyledonous leaves is strongly stimulated by bright white light (WL), at least in part as a result of light-induced acidification of the cell walls. It has been proposed that photosynthetic reactions are required for light-stimulated transport processes across plasma membranes of leaf cells, including proton excretion. The involvement of photosynthesis in growth and wall acidification of primary leaves of bean has been tested by inhibiting photosynthesis in two ways: by reducing chlorophyll content of intact plants with tentoxin (TX) and by treating leaf discs with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Exposure to bright WL stimulated growth of intact leaves of TX-treated plants. Discs excised from green as well as from TX-or DCMU-treated leaves also responded by growing faster in WL, as long as exogenous sucrose was supplied to the photosynthetically inhibited tissues. The WL caused acidification of the epidermal surface of intact TX-leaves, but acidification of the incubation medium by mesophyll cells only occurred when photosynthesis was not inhibited. It is concluded that light-stimulated cell enlargement of bean leaves, and the necessary acidification of epidermal cell walls, are mediated by a pigment other than chlorophyll. Light-induced proton excretion by mesophyll cells, on the other hand, may require both a photosynthetic product (or exogenous sugars) and a non-photosynthetic light effect.

NASA Discipline Number 29-20↗
DOE OSTI2017

Novel insights into ascorbate retention and degradation during the washing and post-harvest storage of spinach and other salad leaves

Post-harvest treatments of pre-packaged salad leaves potentially cause l-ascorbate loss, but the mechanisms of ascorbate degradation remain incompletely understood, especially in planta . We explored the extent and pathways of ascorbate loss in variously washed and stored salad leaves. Ascorbate was assayed by 2,6-dichlorophenolindophenol titration, and pathways were monitored by 14 C-radiolabelling followed by high-voltage electrophoresis. All leaves tested showed ascorbate loss during storage: lettuce showed the greatest percentage loss, wild rocket the least. Spinach leaves were particularly prone to losing ascorbate during washing, especially with simultaneous mechanical agitation; however, washing in the presence of hypochlorite did not significantly increase ascorbate loss. In spinach, [ 14 C]oxalate was the major product of [ 14 C]ascorbate degradation, suggesting that commercial washing causes oxidative stress. This study highlights that ascorbate/dehydroascorbic acid are lost via the oxidative pathway during washing and post-harvest storage of salad leaves. Thus changes to washing procedures could potentially increase the post-harvest retention of ascorbate.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

An Investigation into the Influence of Filler Piper nigrum Leaves Extract on Physicochemical and Antimicrobial Properties of Chitosan/Poly (Vinyl Alcohol) Blend Films

The influence of Piper nigrum (P. nigrum) leaves extract on structural and physicochemical properties of chitosan/poly (vinyl alcohol) (CH/PVA) blend films were studied. The hypothesis of the study was confirmed by using UTM, SEM, AFM, TGA, DSC, XRD, and FTIR studies. Interestingly, increased mechanical properties were observed with inclusion of P. nigrum leaves extract to the CH/PVA blend films. SEM micrographs revealed that there is a smooth homogeneous phase morphology with better compatibility. The results of X-ray diffraction study confirmed that influence of crystallinity on mechanical properties of the blend films. Further, the results of TGA witnessed that addition of P. nigrum leaves extract did not influence much on thermal stability of the CH/PVA blend films. The presence of a single glass transition temperature (T{sub g}) indicated that complete miscibility among the blend components. The result of FTIR study confirmed the presence of a significant interaction among the chitosan, PVA and P. nigrum leaves extract. The water contact angle measurement and the antimicrobial study revealed that CH/PVA/P. nigrum leaves extract blend films showed decreased hydrophobicity and enhanced antimicrobial activity. Hence, this partly stimulated research data obtained from the study might be an advantage for new packaging material preparations in the future.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Evaluating genetic and environmental controls on silicon accumulation in Populus trichocarpa leaves

Background and aims: Silicon (Si) accumulation and formation of non-crystalline silica particles (phytoliths) inside plant cells contribute to plant function, soil carbon storage, and Si reservoirs in soils. A better understanding of how genetic and environmental factors control Si accumulation may improve understanding of Si cycling between plants and soil and its impacts on other ecosystem processes. Methods: This study examined how genetic potential for Si uptake and silicification translated to Si concentrations and phytolith formation in Populus trichocarpa leaves. Leaves were collected from four different genotypes of cultivated poplar trees that were grown in a common garden and possess established differences in leaf-level gene expression related to Si transport and silicification. Scanning electron microscopy and subsequent image analysis were used to quantify Si concentrations and phytolith abundance and features. Results: Phytoliths were identified in nearly all leaves but were often absent at very low (< 0.5 wt.%) Si concentrations at the leaf surface. The proportion of leaf area occupied by phytoliths increased as Si content increased. Silicon content and phytolith abundance at the leaf surface did not vary across genotypes, but surface Si was weakly correlated with plant available Si in soil. Conclusion: Phytoliths were prevalent in P. trichocarpa leaves; however, the genetic potential for Si uptake and silicification at the leaf-level poorly predicted foliar Si and phytolith abundance. Uniformly low expression of Si uptake genes in the roots may have reduced differences across genotypes. Consequently, Si accumulation in leaves was likely more strongly influenced by soil Si bioavailability, phenology, or additional environmental factors.

Image analysis↗
DOE OSTI2020

Imaging Zn and Ni distributions in leaves of different ages of the hyperaccumulator Noccaea caerulescens by synchrotron-based X-ray fluorescence

Mapping of leaves of hyperaccumulators can provide insights into the mechanisms these species utilize to accumulate high metal concentrations. We used synchrotron-based X-ray fluorescence (SXRF) to perform Zn and Ni imaging in leaves of different ages of Noccaea caerulescens. A mature leaf of the related non-hyperaccumulator Thlaspi arvense was also imaged. The concentrations of Zn, Ni, Co, and Cr in N. caerulescens grown on an ultramafic soil were 9-, 10-, 12-, and 3-fold higher than T. arvense. N. caerulescens showed an exceptional ability to accumulate Zn from the soil, posing a bioconcentration factor of 6.7. T. arvense had Zn and Ni distributed uniformly in the leaf blade with doubling fluorescence counts in the tip and margins, suggesting a strategy to excrete metals and avoid toxicity. On the other hand, N. caerulescens displayed distinctly different Zn and Ni accumulation patterns, regardless of the age or metal concentration in the leaves. Zinc was mainly distributed in the cells surrounding the central and secondary veins. Nickel accumulated in the margins and tips of the leaf blade. Finally, given the time required to image large leaves in synchrotron facilities, small leaves can be used to represent the leaf distribution of Zn and Ni in N. caerulescens.

36 MATERIALS SCIENCE↗
DOE OSTI2023

A Wox3 -patterning module organizes planar growth in grass leaves and ligules

Grass leaves develop from a ring of primordial initial cells within the periphery of the shoot apical meristem, a pool of organogenic stem cells that generates all of the organs of the plant shoot. At maturity, the grass leaf is a flattened, strap-like organ comprising a proximal supportive sheath surrounding the stem and a distal photosynthetic blade. The sheath and blade are partitioned by a hinge-like auricle and the ligule, a fringe of epidermally derived tissue that grows from the adaxial (top) leaf surface. Together, the ligule and auricle comprise morphological novelties that are specific to grass leaves. Understanding how the planar outgrowth of grass leaves and their adjoining ligules is genetically controlled can yield insight into their evolutionary origins. Here we use single-cell RNA-sequencing analyses to identify a ‘rim’ cell type present at the margins of maize leaf primordia. Cells in the leaf rim have a distinctive identity and share transcriptional signatures with proliferating ligule cells, suggesting that a shared developmental genetic programme patterns both leaves and ligules. Moreover, we show that rim function is regulated by genetically redundant Wuschel-like homeobox3 (WOX3) transcription factors. Higher-order mutations in maize Wox3 genes greatly reduce leaf width and disrupt ligule outgrowth and patterning. Together, these findings illustrate the generalizable use of a rim domain during planar growth of maize leaves and ligules, and suggest a parsimonious model for the homology of the grass ligule as a distal extension of the leaf sheath margin.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

A Maize GT14 Family Glycosyltransferase Affects Cell Wall Composition and Carbohydrate Export from Source Leaves

Sucrose translocation from photosynthetic leaves to distant parts of a plant, such as seeds and roots, is a critical aspect of plant growth and development and a major determinant of crop yield. To identify genes contributing to this process in maize (Zea mays), we isolated four allelic mutants, carbohydrate partitioning defective7, 48, 49 (cpd7, cpd48, cpd49) and a UniformMu insertion (mu1049954), all of which exhibited reduced growth and fertility and hyperaccumulation of starch and soluble sugars in mature leaves. Consistent with carbohydrate accumulation, cpd7 mutants exhibited reduced sucrose export from mature leaves. Cpd7 encodes a Golgi-resident glucuronosyltransferase belonging to the Glycosyltransferase14 (GT14) family, which is involved in decoration of type II arabinogalactan proteins. No previously described GT14 mutants exhibit reduced sucrose transport or carbohydrate partitioning defects. Additionally, we show that mature leaves of cpd7 mutants have reduced cellulose content and an altered cell wall composition. Further, cpd7 mutants exhibit ectopic phloem lignification likely as a compensatory mechanism for reduced cell wall integrity. Collectively, our data suggest that Cpd7 functions to facilitate cell wall development in the phloem, which is required for efficient sucrose export from mature maize leaves.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Tracking synthesis and turnover of triacylglycerol in leaves

Triacylglycerol (TAG), typically represents <1% of leaf glycerolipids but can accumulate under stress and other conditions or if leaves are supplied with fatty acids, or in plants transformed with regulators or enzymes of lipid metabolism. To better understand the metabolism of TAG in leaves, pulse-chase radiolabelling experiments were designed to probe its synthesis and turnover. When Arabidopsis leaves were incubated with [ 14 C]lauric acid (12:0), a major initial product was [ 14 C]TAG. Thus, despite low steady-state levels, leaves possess substantial TAG biosynthetic capacity. The contributions of diacylglycerol acyltransferase1 and phospholipid:diacylglycerol acyltransferase1 to leaf TAG synthesis were examined by labelling of dgat1 and pdat1 mutants. The dgat1 mutant displayed a major (76%) reduction in [ 14 C]TAG accumulation whereas pdat1 TAG labelling was only slightly reduced. Thus, DGAT1 has a principal role in TAG biosynthesis in young leaves. During a 4h chase period, radioactivity in TAG declined 70%, whereas the turnover of [ 14 C]acyl chains of phosphatidylcholine (PC) and other polar lipids was much lower. Sixty percent of [ 14 C]12:0 was directly incorporated into glycerolipids without modification, whereas 40% was elongated and desaturated to 16:0 and 18:1 by plastids. The unmodified [ 14 C]12:0 and the plastid products of [ 14 C]12:0 metabolism entered different pathways. Although plastid-modified 14 C-labelled products accumulated in monogalactosyldiacylglycerol, PC, phosphatidylethanolamine, and diacylglcerol (DAG), there was almost no accumulation of [ 14 C]16:0 and [ 14 C]18:1 in TAG. Lastly, because DAG and acyl-CoA are direct precursors of TAG, the differential labelling of polar glycerolipids and TAG by [ 14 C]12:0 and its plastid-modified products provides evidence for multiple subcellular pools of both acyl-CoA and DAG.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1969

Leave taking and overtime behavior as related to demographic, health, and job variables

An intra-installation model is formulated that correlates demographic, health and job related variables to the various types and amounts of leave and overtime taking behavior of employees. Statistical comparison of composite health ratings assigned to subjects based upon clinical criteria and bio-statistical data show that those employees who take the most annual leave as well as sick leave are the ones that have the poorest health ratings; employees who put in the most overtime have also the poorest health records. Stress effects of peak activity periods increase use of sick leave immediately after peak activity but not the use of annual leave.

Arnoldi, L. B.↗
NASA NTRS1984

Changes in spectral properties of detached leaves

If leaf senescence can be delayed for several days without significant changes in spectral properties, then samples of leaves at remote test sites could be prepared and shipped to laboratories to measure spectral properties. The changes in spectral properties of detached leaves were determined. Leaves from red birch and red pine were immersed in water or 0.001 M benzylaminopurine (BAP) and stored in plastic bags in the dark at either 5 or 25 C. Total directional-hemispherical reflectance and transmittance of the adaxial surface of birch leaves were measured over the 400 to 1100 nm wavelength region with a spectroradiometer and integrating sphere. Pine needles were taped together and reflectance of the mat of needles was measured. Spectral properties changed less than 5% of initial values during the first week when leaves were stored at 5 C. Storage at 25 C promoted rapid senescence and large changes in spectral properties. BAP delayed, but did not stop, senescence at 25 C.

Daughtry, C. S. T.↗
NASA NTRS2000

Silica Deposition on the Leaves of Mir- and Earth-Grown Super Dwarf Wheat

Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) microanalysis were used to investigate the nature of crystals deposited on leaves of Mir- and Earth-grown Super Dwarf wheat (Triticum aestivum L.) plants. Leaves from these plants exhibited dense and uniformly distributed crystals on leaf abaxial surfaces when viewed by SEM. Young leaves showed that crystals initially accumulated around the stomata on the adaxial surface, but became more dense and uniformly distributed as the leaves aged. EDX microanalyses of the Balkanine (a nutrient charged clinoptilolite zeolite) medium in which the wheat plants were grown showed an elemental pattern similar to that observed on the wheat leaves. The absence of N and P in the Balkanine suggests that they were completely utilized by the plants. Only Si and O were evident in the drying agent, Sorb-it-Silica (trademark), and perhaps could have accounted for some of the Si observed on the plant tissue.

Campbell, William F.↗
NASA NTRS2019

LEAVES: Lofted Environmental and Atmospheric Venus Sensors

LEAVES (Lofted Environmental Atmospheric Venus Sensors) is a design exercise with the goal of dramatically decreasing the cost of obtaining prioritized chemical and physical data in planetary atmospheres. Through the application of a swarm approach this concept parallelizes atmospheric exploration, with geographic coverage far exceeding what is possible with conventional monolithic platforms or sondes. Each unit in the swarm is exceptionally compact, with a powered payload mass of only a few tens of grams and a high-drag, semi-rigid structure that acts to slow each probe as it descends through the atmosphere. This structural design can collapse into a planar form to allow for efficient stowage prior to arrival at the target body. With a total per-unit mass of only 120 g, a fleet of 100 (or more) units can be very reasonably accommodated on a carrier spacecraft.Science operations, which begin when the LEAVES probes reach an altitude of 100 km, are targeted for the cloud-bearing region of Venus' atmosphere. During the roughly 9 hour, terminal velocity descent through the atmosphere, LEAVES collects data of the state and composition of the atmosphere in parallel across multiple units. These data would represent an unprecedented constraint on the distribution and concentration of targeted chemical species, and the detection of local and regional variations in both chemistry and physical properties.A novel and compelling result of this exercise was that the same optimization that produced a structure with an exceptionally low areal mass density (0.126 kg/m2) also resulted in a probe that can be deployed directly from an aerobraking orbit (~140 km at 5 km/s) without the need for aeroshell protection. This translates to a tremendous mass savings and gives LEAVES the flexibility to be carried as a secondary payload aboard either a descending surface probe or an orbital radar mapper. Because such missions are under active development or have already been proposed (but not flown), we infer that LEAVES is well positioned as a technology

Swarm↗
DOE OSTI2020

Effects of exogenous citric acid on the concentration and spatial distribution of Ni, Zn, Co, Cr, Mn and Fe in leaves of Noccaea caerulescens grown on a serpentine soil

The aim of this study was to show the potential of citric acid in increasing the concentration of Ni, Zn, Co, Cr, Mn and Fe in leaves of the hyperaccumulator Noccaea caerulescens. Synchrotron x-ray fluorescence (μ-XRF) images were collected to assess the distribution of metals in leaves. Applying citric acid (20 mmol kg -1 ) to soil increased in 14-, 10-, 7-, 2- and 1.4- fold the concentration of Mn, Fe, Co, Ni, and Cr, respectively, compared to the control. The μ-XRF imaging revealed that Ni and Zn were not spatially correlated across the leaf. We observed a clear partitioning of Zn between veins and surrounding leaf cells while Ni was more evenly distributed between veins and leaf blade. The accumulation of metals in citric acid treated plants did not change the Ni and Zn distribution pattern in leaves but altered the Mn distribution. It seems that Mn reached toxic concentrations in leaves and we hypothesize that a mechanism driven by transpiration through the xylem was used to excrete the metal. Our results show that citric acid can enhance metal accumulation by N. caerulescens and have impact for soil remediation by either decreasing the time for clean up or increasing the access to non-labile pools of metals in soil.

54 ENVIRONMENTAL SCIENCES↗