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Results for “Plant Physiology”

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At least 37 records · Page 2Linked to original sources
USGS1994

Trends in stomatal density and 13C/12C ratios of Pinus flexilis needles during last glacial-interglacial cycle

Measurements of stomatal density and δ 13 C of limber pine ( Pinus flexilis ) needles (leaves) preserved in pack rat middens from the Great Basin reveal shifts in plant physiology and leaf morphology during the last 30,000 years. Sites were selected so as to offset glacial to Holocene climatic differences and thus to isolate the effects of changing atmospheric CO 2 levels. Stomatal density decreased ∼17 percent and δ 13 C decreased ∼1.5 per mil during deglaciation from 15,000 to 12,000 years ago, concomitant with a 30 percent increase in atmospheric CO 2 . Water-use efficiency increased ∼15 percent during deglaciation, if temperature and humidity were held constant and the proxy values for CO 2 and δ 13 C of past atmospheres are accurate. The δ 13 C variations may help constrain hypotheses about the redistribution of carbon between the atmosphere and biosphere during the last glacial-interglacial cycle.

Science↗
USGS2010

Biogeochemical processes in an urban, restored wetland of San Francisco Bay, California, 2007-2009: Methods and data for plant, sediment and water parameters

The restoration of 18 acres of historic tidal marsh at Crissy Field has had great success in terms of public outreach and visibility, but less success in terms of revegetated marsh sustainability. Native cordgrass (Spartina foliosa) has experienced dieback and has failed to recolonize following extended flooding events during unintended periodic closures of its inlet channel, which inhibits daily tidal flushing. We examined the biogeochemical impacts of these impoundment events on plant physiology and on sulfur and mercury chemistry to help the National Park Service land managers determine the relative influence of these inlet closures on marsh function. In this comparative study, we examined key pools of sulfur, mercury, and carbon compounds both during and between closure events. Further, we estimated the net hydrodynamic flux of methylmercury and total mercury to and from the marsh during a 24-hour diurnal cycle. This report documents the methods used and the data generated during the study.

California↗
USGS2022

Terrestrial ecosystem modeling with IBIS: Progress and future vision

Dynamic Global Vegetation Models (DGVM) are powerful tools for studying complicated ecosystem processes and global changes. This review article synthesizes the developments and applications of the Integrated Biosphere Simulator (IBIS), a DGVM, over the past two decades. IBIS has been used to evaluate carbon, nitrogen, and water cycling in terrestrial ecosystems, vegetation changes, land-atmosphere interactions, land-aquatic system integration, and climate change impacts. Here we summarize model development work since IBIS v2.5, covering hydrology (evapotranspiration, groundwater, lateral routing), vegetation dynamics (plant functional type, land cover change), plant physiology (phenology, photosynthesis, carbon allocation, growth), biogeochemistry (soil carbon and nitrogen processes, greenhouse gas emissions), impacts of natural disturbances (drought, insect damage, fire) and human induced land use changes, and computational improvements. We also summarize IBIS model applications around the world in evaluating ecosystem productivity, carbon and water budgets, water use efficiency, natural disturbance effects, and impacts of climate change and land use change on the carbon cycle. Based on this review, visions of future cross-scale, cross-landscape and cross-system model development and applications are discussed.

Journal of Resources and Ecology↗
USGS1990

Sago pondweed (Potamogeton pectinatus L.): A literature review

Sago pondweed ( Potamogeton pectinatus L.) is a submersed macrophyte of nearly cosmopolitan distribution. The plant is of worldwide importance as a waterfowl food but also can be a nuisance in irrigation canals and recreational areas. The plant reproduces by many different means, depending on habitat and environmental stress. Several genetic ecotypes have evolved. Most important as waterfowl food are the turions (tubers), vegetative propagules rich in carbohydrates that are mostly buried in bottom sediments. In temperate wetlands, most turions sprout in spring, making sago behave as an annual. Drupelets (seeds) are the sexual propagules of sago and provide a mechanism for sago to survive periods of drought and excessive water salinity. Drupelets can be washed ashore or carried by birds for long distances. Sago decomposes rapidly at senescence, annually in temperate wetlands. Sago is mostly found in semipermanently or permanently flooded mixosaline lacustrine, palustrine, and riverine wetlands < 2.5 m deep, where fetches are not large or currents are < 1 m/s. Sago seems to prefer stable water levels but can tolerate significant water level fluctuations. Among the Potamogetons, only sago tolerates high salinity, pH, and alkalinity, but it fares poorly among specialist taxa in acidic or nutrient-poor waters. Sago is highly tolerant of eutrophic waters, and it can be the only species of submersed macrophyte present in heavily polluted sites. Sago grows in nearly all bottom substrates. Turbidity is the factor that most frequently limits sago growth. Sago often occurs in monotypic stands but can grow with many other submersed and emergent macrophytes. Dominance by sago in certain wetlands sometimes alternates with dominance by other submersed macrophytes when salinities or other environmental factors change. Sago also can be associated with a large variety of unattached filamentous, planktonic, or epiphytic algae. Increased turbidity caused by planktonic algae often is responsible for lowered sago production. Less common biotic limiting factors are organic pollutants and consumption and uprooting by waterfowl and fish. Sago provides food or shelter for amphibians, reptiles, fish, and mammals. The greatest value of sago in North America is as food for migrant and staging waterfowl, primarily diving ducks and swans. Sago beds also provide habitat for a large complex of invertebrates (an important food source for young waterfowl), but direct consumption of living sago by invertebrates is negligible. Sago has been propagated for many years-indoors, as an experimental organism for work in plant physiology or herbicide testing, and outdoors, for purposes of attracting waterfowl. Much work has also been done developing methods to control excessive sago growth in fishponds and irrigation canals. Future research should concentrate on (1) determining, in a variety of wetland types, the causes of light-limiting turbidity that often suppresses sago growth, (2) understanding the ways in which human activities on and near wetlands affect sago production, and (3) developing reliable and predictable techniques to stimulate sago production for waterfowl by using water level manipulations and other means, in a variety of environmental settings.

Resource Publication↗
USGS2004

Estimating disturbance effects from military training using developmental instability and physiological measures of plant stress

We used developmental instability, water potential, and variable fluorescence to determine if populations of winged sumac (Rhus copallinum) were being negatively effected by military training disturbance. We established nine sites that represented a land-use disturbance gradient with three impact levels (low, medium, and high), the effects mostly due to mechanized infantry training maneuvers. Although mean values of developmental instability, water potential, and variable fluorescence differed significantly among sites, the patterns did not consistently differentiate sites relative to the disturbance gradient. At the population level, some measures of developmental instability and variable fluorescence were positively correlated. All nine sites consisted of habitat mosaics, with the abundance of higher quality habitat patches and canopy gaps closely related to habitat impacts. It may be that R. copallinum is selecting similar micro-environments at all sites and therefore minimizing inter-site variation in stress measures, despite large differences in overall habitat condition. Our results call for caution in developing ecological indicators using the response of physiological and morphological measures from a single plant species. ?? 2003 Elsevier Ltd. All rights reserved.

Ecological Indicators↗
USGS2014

Functional diversity supports the physiological tolerance hypothesis for plant species richness along climatic gradients

1. The physiological tolerance hypothesis proposes that plant species richness is highest in warm and/or wet climates because a wider range of functional strategies can persist under such conditions. Functional diversity metrics, combined with statistical modeling, offer new ways to test whether diversity-environment relationships are consistent with this hypothesis. 2. In a classic study by R. H. Whittaker (1960), herb species richness declined from mesic (cool, moist, northerly) slopes to xeric (hot, dry, southerly) slopes. Building on this dataset, we measured four plant functional traits (plant height, specific leaf area, leaf water content and foliar C:N) and used them to calculate three functional diversity metrics (functional richness, evenness, and dispersion). We then used a structural equation model to ask if ‘functional diversity’ (modeled as the joint responses of richness, evenness, and dispersion) could explain the observed relationship of topographic climate gradients to species richness. We then repeated our model examining the functional diversity of each of the four traits individually. 3. Consistent with the physiological tolerance hypothesis, we found that functional diversity was higher in more favorable climatic conditions (mesic slopes), and that multivariate functional diversity mediated the relationship of the topographic climate gradient to plant species richness. We found similar patterns for models focusing on individual trait functional diversity of leaf water content and foliar C:N. 4. Synthesis. Our results provide trait-based support for the physiological tolerance hypothesis, suggesting that benign climates support more species because they allow for a wider range of functional strategies.

Oregon↗
USGS2018

Snowmelt timing regulates community composition, phenology, and physiological performance of alpine plants

The spatial patterning of alpine plant communities is strongly influenced by the variation in physical factors such as temperature and moisture, which are strongly affected by snow depth and snowmelt patterns. Earlier snowmelt timing and greater soil-moisture limitations may favor wide-ranging species adapted to a broader set of ecohydrological conditions than alpine-restricted species. We asked how plant community composition, phenology, plant water relations, and photosynthetic gas exchange of alpine-restricted and wide-ranging species differ in their responses to a ca. 40-day snowmelt gradient in the Colorado Rocky Mountains ( Lewisia pygmaea , Sibbaldia procumbens , and Hymenoxys grandiflora were alpine-restricted and Artemisia scopulorum , Carex rupestris , and Geum rossii were wide-ranging species). As hypothesized, species richness and foliar cover increased with earlier snowmelt, due to a greater abundance of wide-ranging species present in earlier melting plots. Flowering initiation occurred earlier with earlier snowmelt for 12 out of 19 species analyzed, while flowering duration was shortened with later snowmelt for six species (all but one were wide-ranging species). We observed >50% declines in net photosynthesis from July to September as soil moisture and plant water potentials declined. Early-season stomatal conductance was higher in wide-ranging species, indicating a more competitive strategy for water acquisition when soil moisture is high. Even so, there were no associated differences in photosynthesis or transpiration, suggesting no strong differences between these groups in physiology. Our findings reveal that plant species with different ranges (alpine-restricted vs. wide-ranging) could have differential phenological and physiological responses to snowmelt timing and associated soil moisture dry-down, and that alpine-restricted species’ performance is more sensitive to snowmelt. As a result, alpine-restricted species may serve as better indicator species than their wide-ranging heterospecifics. Overall, alpine community composition and peak % cover are strongly structured by spatio-temporal patterns in snowmelt timing. Thus, near-term, community-wide changes (or variation) in phenology and physiology in response to shifts in snowmelt timing or rates of soil dry down are likely to be contingent on the legacy of past climate on community structure.

Frontiers in Plant Science↗
USGS2020

Seasonal and individual event-responsiveness are key determinants of carbon exchange across plant functional types

Differentiation in physiological activity is a critical component of resource partitioning in resource-limited environments. For example, it is crucial to understand how plant physiological performance varies through time for different functional groups to forecast how terrestrial ecosystems will respond to change. Here, we tracked the seasonal progress of 13 plant species representing C 3 shrub, perennial C 3 and C 4 grass, and annual forb functional groups of the Colorado Plateau, USA. We tested for differences in carbon assimilation strategies and how photosynthetic rates related to recent, seasonal, and annual precipitation and temperature variables. Despite seasonal shifts in species presence and activity, we found small differences in seasonally weighted annual photosynthetic rates among groups. However, differences in the timing of maximum assimilation ( A net ) were strongly functional group-dependent. C 3 shrubs employed a relatively consistent, low carbon capture strategy and maintained activity year-round but switched to a rapid growth strategy in response to recent climate conditions. In contrast, grasses maintained higher carbon capture during spring months when all perennials had maximum photosynthetic rates, but grasses were dormant during months when shrubs remained active. Perennial grass A net rates were explained in part by precipitation accumulated during the preceding year and average maximum temperatures during the past 48 h, a result opposite to shrubs. These results lend insight into diverse physiological strategies and their connections to climate, and also point to the potential for shrubs to increase in abundance in response to increased climatic variability in drylands, given shrubs’ ability to respond rapidly to changing conditions.

Oecologia↗
USGS2001

Monitoring the effect of poplar trees on petroleum-hydrocarbon and chlorinated-solvent contaminated ground water

At contaminated groundwater sites, poplar trees can be used to affect ground-water levels, flow directions, and ultimately total groundwater and contaminant flux to areas downgradient of the trees. The magnitude of the hydrologic changes can be monitored using fundamental concepts of groundwater hydrology, in addition to plant physiology-based approaches, and can be viewed as being almost independent of the contaminant released. The affect of poplar trees on the fate of groundwater contaminants, however, is contaminant dependent. Some petroleum hydrocarbons or chlorinated solvents may be mineralized or transformed to innocuous compounds by rhizospheric bacteria associated with the tree roots, mineralized or transformed by plant tissues in the transpiration stream or leaves after uptake, or passively volatilized and rapidly dispersed or oxidized in the atmosphere. These processes also can be monitored using a combination of physiological- or geochemical-based field or laboratory approaches. When combined, such hydrologic and contaminant monitoring approaches can result in a more accurate assessment of the use of poplar trees to meet regulatory goals at contaminated groundwater sites, verify that these goals continue to be met in the future, and ultimately lead to a consensus on how the performance of plant-based remedial strategies (phytoremediation) is to be assessed.

International Journal of Phytoremediation↗
USGS2020

A modeling workflow that balances automation and human intervention to inform invasive plant management decisions at multiple spatial scales

Predictions of habitat suitability for invasive plant species can guide risk assessments at regional and national scales and inform early detection and rapid-response strategies at local scales. We present a general approach to invasive species modeling and mapping that meets objectives at multiple scales. Our methodology is designed to balance trade-offs between developing highly customized models for few species versus fitting non-specific and generic models for numerous species. We developed a national library of environmental variables known to physiologically limit plant distributions and relied on human input based on natural history knowledge to further narrow the variable set for each species before developing habitat suitability models. To ensure efficiency, we used largely automated modeling approaches and human input only at key junctures. We explore and present uncertainty by using two alternative sources of background samples, including five statistical algorithms, and constructing model ensembles. We demonstrate the use and efficiency of the Software for Assisted Habitat Modeling [SAHM 2.1.2], a package in VisTrails, which performs the majority of the modeling analyses. Our workflow includes solicitation of expert feedback on model outputs such as spatial prediction results and variable response curves, and iterative improvement based on new data availability and directed field validation of initial model results. We highlight the utility of the models for decision-making at regional and local scales with case studies of two plant species that invade natural areas: fountain grass ( Pennisetum setaceum ) and goutweed ( Aegopodium podagraria ). By balancing model automation with human intervention, we can efficiently provide land managers with mapped predicted distributions for multiple invasive species to inform decisions across spatial scales.

PLoS ONE↗
USGS2001

Fungal symbiosis from mutualism to parasitism: who controls the outcome, host or invader?

Plant symbiotic fungi are generally thought to express a single lifestyle that might increase (mutualism), decrease (parasitism), or have no influence (commensalism) on host fitness. However, data are presented here demonstrating that plant pathogenic Colletotrichum species are able to asymptomatically colonize plants and express nonpathogenic lifestyles. Experiments were conducted in growth chambers and plant colonization was assessed by emergence of fungi from surface sterilized plant tissues. Expression of symbiotic lifestyles was assessed by monitoring the ability of fungi to confer disease resistance, drought tolerance and growth enhancement. Several pathogenic Colletotrichum species expressed either mutualistic or commensal lifestyles in plants not known to be hosts. Mutualists conferred disease resistance, drought tolerance, and/or growth enhancement to host plants. Lifestyle-altered mutants expressing nonpathogenic lifestyles had greater host ranges than the parental wildtype isolate. Successive colonization studies indicated that the ability of a symbiont to colonize a plant was dependent on previous colonization events and the lifestyles expressed by the initial colonizing fungus. The results indicate that the outcome of symbiosis is controlled by the plant's physiology. ?? New Phytologist.

New Phytologist↗
USGS1999

Biochemical analysis of plant protection afforded by a nonpathogenic endophytic mutant of Colletotrichum magna

A nonpathogenic mutant of Colletotrichum magna (path-1) was previously shown to protect watermelon (Citrullus lanatus) and cucumber (Cucumis sativus) seedlings from anthracnose disease elicited by wild-type C. magna. Disease protection was observed in stems of path-1-colonized cucurbits but not in cotyledons, indicating that path-1 conferred tissue-specific and/or localized protection. Plant biochemical indicators of a localized and systemic (peroxidase, phenylalanine ammonia-lyase, lignin, and salicylic acid) 'plant-defense' response were investigated in anthracnose-resistant and -susceptible cultivars of cucurbit seedlings exposed to four treatments: (1) water (control), (2) path-1 conidia, (3) wild-type conidia, and (4) challenge conditions (inoculation into path-1 conidia for 48 h and then exposure to wild-type conidia). Collectively, these analyses indicated that disease protection in path-1 colonized plants was correlated with the ability of these plants to mount a defense response more rapidly and to equal or greater levels than plants exposed to wild-type C. magna alone. Watermelon plants colonized with path-1 were also protected against disease caused by Colletotrichum orbiculare and Fusarium oxysporum. A model based on the kinetics of plant-defense activation is presented to explain the mechanism of path-1-conferred disease protection.

Plant Physiology↗
USGS1982

Gas exchange characteristics of the submerged aquatic Crassulacean acid metabolism plant, Isoetes howellii

The submerged aquatic plant Isoetes howellii Engelmann possesses Crassulacean acid metabolism (CAM) comparable to that known from terrestrial CAM plants. Infrared gas analysis of submerged leaves showed Isoetes was capable of net CO 2 uptake in both light and dark. CO 2 uptake rates were a function of CO 2 levels in the medium. At 2,500 microliters CO 2 per liter (gas phase, equivalent to 1.79 milligrams per liter aqueous phase), Isoetes leaves showed continuous uptake in both the light and dark. At this CO 2 level, photosynthetic rates were light saturated at about 10% full sunlight and were about 3-fold greater than dark CO 2 uptake rates. In the dark, CO 2 uptake rates were also a function of length of time in the night period. Measurements of dark CO 2 uptake showed that, at both 2,500 and 500 microliters CO 2 per liter, rates declined during the night period. At the higher CO 2 level, dark CO 2 uptake rates at 0600 h were 75% less than at 1800 h. At 500 microliters CO 2 per liter, net CO 2 uptake in the dark at 1800 h was replaced by net CO 2 evolution in the dark at 0600 h. At both CO 2 levels, the overnight decline in net CO 2 uptake was marked by periodic bursts of accelerated CO 2 uptake. CO 2 uptake in the light was similar at 1% and 21% O 2 , and this held for leaves intact as well as leaves split longitudinally. Estimating the contribution of light versus dark CO 2 uptake to the total carbon gain is complicated by the diurnal flux in CO 2 availability under field conditions.

Plant Physiology↗
USGS1984

Hydrogen, oxygen, and carbon isotope ratios of cellulose from submerged aquatic Crassulacean acid metabolism and non-Crassulacean acid metabolism plants

Isotope ratios of cellulose and cellulose nitrate from aquatic Crassulacean acid metabolism (CAM) and non-CAM plants were determined. Cellulose oxygen istope ratios for all plants that grew together were virtually identical, whereas large differences were observed for hydrogen isotope ratios of cellulose nitrate between CAM and non-CAM plants. Carbon isotope ratios of cellulose nitrate did not differentiate CAM from non-CAM plants.

Plant Physiology↗
USGS1984

Carbon assimilation characteristics of the aquatic CAM plant Isoetes howellii

The relationship between malic acid production and carbon assimilation was examined in the submerged aquatic Crassulacean acid metabolism (CAM) plant, Isoetes howellii Engelmann. Under natural conditions free-CO 2 level in the water was highest at 0600 hours and 14 CO 2 assimilation rates in I. howellii were also highest at this time. After 0900 hours there was a similar pattern in (a) rate of free-CO 2 depletion from the water, (b) reduction of carbon assimilation rates, and (c) rate of deacidification in leaves. Rates of daytime deacidification increased under CO 2 -free conditions and as irradiance intensity increased. Nighttime CO 2 uptake was estimated to contribute one-third to one-half of the total daily gross carbon assimilation. CO 2 uptake, however, accounted for only one-third to one-half of the overnight malic acid accumulation. Internal respiratory CO 2 may be a substrate for a large portion of overnight acid accumulation as leaves incubated overnight without CO 2 accumulated substantial levels of malic acid. Loss of CAM occurred in emergent leaf tips even though submerged bases continued CAM. Associated with loss of CAM in aerial leaves was an increase in total chlorophyll, a/b ratio, and carotenoids, and a decrease in leaf succulence. δ 13 C values of I. howellii were not clearly distinguishable from those for associated non-CAM submerged macrophytes.

Plant Physiology↗
USGS2023

Divergent physiological responses of hydric and mesic riparian plant species to a Colorado River experimental flow

Riparian plant species can differ in their responses to streamflow variation in ways that strongly influence the composition and functioning of riparian plant communities. Quantifying these differences and the potential asymmetry of responses to low- versus high-flow phases of stream fluctuations is important for predicting and managing vegetation responses to variation in flow regimes. We measured the physiological response of two riparian plant species with different habitat preferences to an experimental flow that progressed from a low-flow to high-flow phase. Schedonorous arundinaceus , a hydric grass growing in near-channel habitat, exhibited significant and biologically substantial declines in stem water potential (SWP) during the low-flow phase of the experiment and a saturating increase in leaf relative water content (LRWC) during the high-flow phase. These patterns are consistent with cavitation risk in response to low-flow anomalies and saturating responses to high-flow anomalies in this hydric species. Pluchea sericea , a mesic shrub growing at intermediate elevations above the channel, exhibited a decrease in LRWC during the low-flow phase and an increase in SWP during the high-flow phase. These patterns are consistent with protection from stem cavitation risk during drought through leaf dehydration and opportunistic increases in water status in response to high-flow anomalies in this mesic species. The asymmetrical responses of both species to low- versus high-flow phases demonstrate unique physiological responses to flow anomalies of contrasting directions attributable to species habitat preferences and functional strategies that can be used by managers to predict non-linear vegetation responses to flow variation.

Plant Ecology↗
USGS2020

Life-history plasticity and water-use trade-offs associated with drought resistance in a clade of California jewelflowers

Water limitation is a primary driver of plant geographic distributions and individual plant fitness. Drought resistance is the ability to survive and reproduce despite limited water, and numerous studies have explored its physiological basis in plants. However, it is unclear how drought resistance and trade-offs associated with drought resistance evolve within plant clades. We quantified the relationship between water availability and fitness for 13 short-lived plant taxa in the Streptanthus clade that vary in their phenology and the availability of water in the environments where they occur. We derived two parameters from these relationships: plant fitness when water is not limiting and the water inflection point (WIF), the watering level at which additional water is most efficiently turned into fitness. We used phylogenetic comparative methods to explore trade-offs related to drought resistance and trait plasticity and the degree to which water relationship parameters are conserved. Taxa from drier climates produced fruits at the lowest water levels, had a lower WIF, flowered earlier, had shorter life spans, had greater plastic water-use efficiency (WUE), and had lower fitness at nonlimiting water. In contrast, later-flowering Streptanthus taxa from less xeric climates experienced high fitness at nonlimiting water but had no fitness at the lowest water levels. Across the clade, we found a trade-off between drought resistance and fitness at high water, though a single ruderal species was an outlier in this relationship. Our results suggest that drought escape trades off with maximal fitness under nonlimiting water, and both are tied to phenology. We also found that variation in trait plasticity determines how different plant species produce fitness over a water gradient.

California↗