CDNA microarray assessment for ozone-stressed Arabidopsis thaliana

Various detrimental factors in the environment damage plants, resulting in growth inhibition or withering. However, it is not easy to identify causal factors by visually inspecting the damaged plants. Therefore, we have developed a sensitive and reliable method for plant diagnosis, based on measuring changes in expression of a set of genes in a DNA microarray. With this method, we have been able to detect and discriminate between plants stressed by ozone, drought, or wounding.     

Eucalyptus ESTs related to genes for oxidative stress

Oxidative stress generating active oxygen species has been proved to be one of the underlying agents causing tissue injury after the exposure of Eucalyptus (Eucalyptus spp.) plants to a wide variety of stress conditions. The objective of this study was to perform data mining to identify favorable genes and alleles associated with the enzyme systems superoxide dismutase, catalase, peroxidases, and glutathione S-transferase that are related to tolerance for environmental stresses and damage caused by pests, diseases, herbicides, and by weeds themselves. This was undertaken by using the eucalyptus expressed-sequence database (https//forests.esalq.usp.br). The alignment results between amino acid and nucleotide sequences indicated that the studied enzymes were adequately represented in the ESTs database of the FORESTs project.     

Mechanisms of silicon-mediated alleviation of abiotic stresses in higher plants: a review

Although silicon (Si) is the second most abundant element both on the surface of the Earth's crust and in soils, it has not yet been listed among the essential elements for higher plants. However, the beneficial role of Si in stimulating the growth and development of many plant species has been generally recognized. Silicon is known to effectively mitigate various abiotic stresses such as manganese, aluminum and heavy metal toxicities, and salinity, drought, chilling and freezing stresses. However, mechanisms of Si-mediated alleviation of abiotic stresses remain poorly understood. The key mechanisms of Si-mediated alleviation of abiotic stresses in higher plants include: (1) stimulation of antioxidant systems in plants, (2) complexation or co-precipitation of toxic metal ions with Si, (3) immobilization of toxic metal ions in growth media, (4) uptake processes, and (5) compartmentation of metal ions within plants. Future research needs for Si-mediated alleviation of abiotic stresses are also discussed.     

Air Pollution Research Needs: Herbaceous and Ornamental Plants and Agriculturally Generated Pollutants

Effects of various air pollutants on economically important crops and ornamentals have been studied since before the turn of the century.

Summaries of this research on the effects of air pollutants, that have appeared in criteria documents developed by the Environmental Protection Agency, should be reviewed with respect to differences in plant susceptibility found in various regions of the country. These susceptibility differences are associated with variations in both environmental conditions and distribution of pollutants. Research efforts on air pollution injury to vegetation have often been poorly coordinated leaving many gaps in our knowledge. A better assessment of the impact of air pollution on vegetation is required to attain realistic controls for pollutants affecting agriculture. Research areas of major concern include: baseline information on effects of pollutants on agricultural productivity; dose-response information to support predictive mathematical models for acute and chronic studies of growth, yield, and quality effects; effects of pollutants interacting with other pollutants and with insects and plant diseases; mechanisms of pollutant action; genetic changes related to pollutant effects; effects of environmental stresses on plant response to pollutants; evaluation of plants including soil microbes as pollutant sinks; development of techniques to minimize pollutant effects; and, the effects of agricultural chemicals as air pollutants. There is a need for studies that consider the whole plant in its natural environment. Conceptual models interrelating pollutant effects and their interactions and ultimately mathematical models will be needed to develop an intelligent approach to land management. The effects of agriculturally produced pollutants on plants and other receptors must be identified and quantified.     

Characterizing ammonia emissions from swine farms in eastern North Carolina: part 2--potential environmentally superior technologies for waste treatment

The need for developing environmentally superior and sustainable solutions for managing the animal waste at commercial swine farms in eastern North Carolina has been recognized in recent years. Program OPEN (Odor, Pathogens, and Emissions of Nitrogen), funded by the North Carolina State University Animal and Poultry Waste Management Center (APWMC), was initiated and charged with the evaluation of potential environmentally superior technologies (ESTs) that have been developed and implemented at selected swine farms or facilities. The OPEN program has demonstrated the effectiveness of a new paradigm for policy-relevant environmental research related to North Carolina's animal waste management programs. This new paradigm is based on a commitment to improve scientific understanding associated with a wide array of environmental issues (i.e., issues related to the movement of N from animal waste into air, water, and soil media; the transmission of odor and odorants; disease-transmitting vectors; and airborne pathogens). The primary focus of this paper is on emissions of ammonia (NH3) from some potential ESTs that were being evaluated at full-scale swine facilities. During 2-week-long periods in two different seasons (warm and cold), NH3 fluxes from water-holding structures and NH3 emissions from animal houses or barns were measured at six potential EST sites: (1) Barham farm--in-ground ambient temperature anaerobic digester/energy recovery/greenhouse vegetable production system; (2) BOC #93 farm--upflow biofiltration system--EKOKAN; (3) Carrolls farm--aerobic blanket system--ISSUES-ABS; (4) Corbett #1 farm--solids separation/ gasification for energy and ash recovery centralized system--BEST; (5) Corbett #2 farm--solid separation/ reciprocating water technology--ReCip; and (6) Vestal farm--Recycling of Nutrient, Energy and Water System--ISSUES-RENEW. The ESTs were compared with similar measurements made at two conventional lagoon and spray technology (LST) farms (Moore farm and Stokes farm). A flow-through dynamic chamber system and two sets of open-path Fourier transform infrared (OP-FTIR) spectrometers measured NH3 fluxes continuously from water-holding structures and emissions from housing units at the EST and conventional LST sites. A statistical-observational model for lagoon NH3 flux was developed using a multiple linear regression analysis of 15-min averaged NH3 flux data against the relevant environmental parameters measured at the two conventional farms during two different seasons of the year. This was used to compare the water-holding structures at ESTs with those from lagoons at conventional sites under similar environmental conditions. Percentage reductions in NH3 emissions from different components of each potential EST, as well as the whole farm on which the EST was located were evaluated from the estimated emissions from water-holding structures, barns, etc., all normalized by the appropriate nitrogen excretion rate at the potential EST farm, as well as from the appropriate conventional farm. This study showed that ammonia emissions were reduced by all but one potential EST for both experimental periods. However, on the basis of our evaluation results and analysis and available information in the scientific literature, the evaluated alternative technologies may require additional technical modifications to be qualified as unconditional ESTs relative to NH3 emissions reductions.     

Mycorrhizal mediation of plant response to atmospheric change: Air quality concepts and research considerations

The term 'global climate change' encompasses many physical and chemical changes in the atmosphere that have been induced by anthropogenic pollutants. Increases in concentrations of CO2 and CH4 enhance the 'greenhouse effect' of the atmosphere and may contribute to changes in temperature and precipitation patterns at the earth's surface. Nitrogen oxides and SO2 are phytotoxic and also react with other pollutants to produce other phytotoxins in the troposphere such as O3 and acidic substances. However, release of chlorofluorocarbons into the atmosphere may cause depletion of stratospheric O3, increasing the transmittance of ultraviolet-B (UV-B) radiation to the earth's surface. Increased intensities of UV-B could affect plants and enhance photochemical reactions that generate some phytotoxic pollutants. The role of mycorrhizae in plant responses to such stresses has received little attention. Although plans for several research programs have acknowledged the importance of drought tolerance and soil fertility in plant responses to atmospheric stresses, mycorrhizae are rarely targeted to receive specific investigation. Most vascular land plants form mycorrhizae, so the role of mycorrhizae in mediating plant responses to atmospheric change may be an important consideration in predicting effects of atmospheric changes on plants in managed and natural ecosystems.     

植物细胞色素P450酶系的研究进展及其与外来物质的关系

植物细胞色素P45 0是分子量为 40— 60KD、结构类似的一类血红素 硫铁蛋白。它以可溶性和膜结合两种形态存在于植物细胞内 ,可催化多种化学反应 ,在防御植物免受有害物质侵害方面具有重要作用。目前已克隆 90多个植物细胞色素P45 0基因。本文概述了植物P45 0基因表达调控与环境、发育、组织特异性关系的研究进展。认为植物P45 0同工酶在环境毒物生物修复和在抗外源毒素的转基因植物方面具有很高的应用前景     

Use of freshwater plants for phytotoxicity testing: a review

Phytotoxicity data for aquatic plants have served a relatively minor role in regulatory decisions concerning the environmental hazard of most potential contaminants. A variety of phytotoxicity tests have been conducted with freshwater green algae, duckweed, blue-green algae, diatoms and rooted macrophytes (whole plants and seeds). Several test methods have been standardized for microalgae which are used primarily with chemicals, effluents, contaminated sediment elutriates and hazardous waste leachates. Current scientific understanding concerning the phytotoxic effects of these contaminants is based mostly on results for a few green algae. The greatest limitation of these results is their uncertain environmental relevance due to the large interspecific variation in response of standard algal test species and the unrealistic experimental test conditions. Results of the few field validation toxicity tests conducted to resolve this uncertainty have been chemical-specific and unpredictable. Aquatic vascular plants have been used less frequently than algae as test species. Duckweeds have been used more often than rooted submersed species but the uncertain nature of their sensitivities relative to animal and other plant species has limited their use. Regulatory interest in wetland protection, contaminated sediment evaluations and sediment quality criteria development will result in increased use of whole rooted plants and their seeds as test species. Overall, regardless of the test species, if phytotoxicity data are to be more available and effective in the hazard assessment process, additional information concerning species sensitivity, and environmental relevance of the results will be needed.     

Fiber Glass Fabric Filters for High Temperature Dust and Fume Control

Foliar markings on vegetation have proven a highly sensitive criterion for the presence of many air pollutants; proper evaluation of such effects can serve as a valuable and inexpensive tool for delineating an air pollution condition. Injury symptoms from fluoridt, sulfur dioxide, photochemical oxidants and other pollutants have been described and can be recognized by experienced observers. Field studies provide a valuable technique for appraising an air pollution problem when diagnosis is not confused by other factors. Careful inspection can avert difficulties arising in diagnosis where similar symptoms are produced by agents other than air pollutants. Several factors must be considered in appraising injury. These include a knowledge of the relative sensitivity of plant species to various pollutants, the syndrome of injury on a number of plants and species, and distribution and geographic relation of affected plants to the suspected source. Background information on cultural, environmental, disease and insect conditions which might be responsible for, or modify, foliar markings or chronic effects in question must also be understood. For some pollutants a chemical analysis of foliage and air may prove helpful. When these factors are studied, the presence, distribution and magnitude of an air pollution situation can be evaluated, thus providing a sensitive criterion of air quality.     

Exotic gene expression in transgenic plants as a tool for monitoring environmental pollution

Environmental monitoring can benefit from the application of molecular and biochemical techniques as biomarkers. In principle, molecular biomarkers may have some advantage over more classical, organismal level markers because of their sensitivity, efficiency and reproducibility. Nevertheless, some disadvantages such as the cost, resource requirements and lack of specificity have limited their widespread use. Molecular genetics and recombinant DNA technologies, however, allow to improve simplicity and cost, together with reliability, efficiency and sensitivity, of molecular biomarkers. The stress inducible promoter of the barley gene Hvhspl7, which is induced by a number of environmental stress (including some heavy metals), has been fused to the reporter gene GUS in a plasmid. This plasmid was used for stable transformation of tobacco. Some of the transgenic plants obtained after selection showed enhanced GUS expression after exposure to some heavy metals. Maintenance of the plants for three generations, and the analysis of the response to treatments, suggest that these transgenic plants may be utilised as an affordable biomarker for monitoring heavy metal pollution.     

Heat and mass transfer in the vadose zone with plant roots

The vadose zone is the intermediate medium between the atmosphere and groundwater. The modeling of the processes taking place in the vadose zone needs different approaches to those needed for groundwater transport problems because of the marked changes in environmental conditions affecting the vadose zone. A mathematical model to simulate the water flow, and the fate and transport of recalcitrant contaminants was developed, which could be applied to various bioremediation methods such as phytoremediation and natural attenuation in the vadose zone. Two-phase flow equations and heat flux models were used to develop the model. Surface energy, balance equations were used to estimate soil surface temperature, and root growth and root distribution models were incorporated to represent the special contribution of plant mots in the vegetated soils. Interactions between the roots and environmental conditions such as temperature and water content were treated by incorporating a feedback mechanism that made allowance for the effects of water and temperature stresses on root distribution and water uptake by roots. In conducting the modeling study, Johnson grass and unplanted soil were simulated to compare the effect of root water uptake on soil water content. After the numerical experiments were conducted to investigate model behavior, the proposed model was applied to estimate actual water flow and heat flow in field lysimeter experiments over a 1-year period. Root growth and distribution for Johnson grass and rye grass were simulated to compare the warm season grass to the cold season grass. A significant agreement was observed between the simulations and measured data.     

Interaction between ozone and winter stress

In some countries, ozone (O3) is primarily a summer pollutant, but in much of Europe, elevated concentrations occur outside the growing season so perennials and over-wintering annuals may be subjected to the combined stresses of pollution, plus chilling, freezing, and winter desiccation. It is recognised that some air pollutants modify the response of plants to environmental stress, but little is known of interactions involving O3. This paper is part of a programme concerned with the effects of O3 on resistance to chilling, freezing, and winter desiccation. Pea (Pisum sativum L.) was used as a convenient model to confirm that O3 affects freezing resistance. The experiment also served as a further evaluation of the use of induced chlorophyll fluorescence kinetics to detect latent O3 injury. Two cultivars, 'Feltham First' and 'Conquest', were fumigated for 7 days, 7 h day(-1). Diffusive resistance and induced fluorescence were recorded daily during the period, then the plants were hardened at 4 degrees C day/2 degrees C night before exposure to 0, -2, -4, -6 and -8 degrees C. Ozone (0.075 ppm; 150 microg O3 m(-3)) caused stomatal closure in both cultivars, but the response was more rapid in 'Conquest'. There were also rapid effects on fluorescence kinetics, and it was concluded that FR, the rate of rise of induced fluorescence, is a useful parameter for indicating latent injury and for distinguishing between cultivars of different sensitivity. Exposure to O3 increased freezing injury and led to greater electrolyte leakage. The freezing resistance of 'Feltham First' was more affected than that of 'Conquest', probably because of the slower stomatal response to the pollutant leading to greater flux of O3 to the internal tissues. It is concluded that interactions involving pollutants and winter stress have implications for crop loss assessment. Perennials and over-wintering annuals should be exposed to the full range of environmental stresses.     

Plant steroid hormones produced under Ni stress are involved in the regulation of metal uptake and oxidative stress in Brassica juncea L

Brassinosteroids (BRs) are involved in the amelioration of various biotic and abiotic stresses. With an aim to explore the role of BRs under heavy metal stress, plants of Brassica juncea L. were grown in pots. The plants were subjected to various concentrations of Nickel metal (0.0, 0.2, 0.4 and 0.6 mM) and harvested on 60th day in order to observe the expression of these hormones. The isolated BRs from the leaves of Brassica plants characterized by GC-MS include 24-Epibrassinolide (24-EBL), Castasterone, Dolicholide and Typhasterole. The effect of isolated 24-EBL was studied on Ni metal uptake and antioxidative defense system in 60 d old plants of Brassica. It was observed that 24-EBL significantly increased the activities of stress ameliorating enzymes and lowered the metal uptake in plants. This is the first report in B. juncea L. plants showing the expression of BRs under metal treatments and effect of the isolated 24-EBL on metal uptake and in oxidative stress management.     

Modeling the effects of ozone on soybean growth and yield

A simple mechanistic model was developed based on an existing growth model in order to address the mechanisms of the effects of ozone on growth and yield of soybean [Glycine max. (L.) Merr. 'Davis'] and interacting effects of other environmental stresses. The model simulates daily growth of soybean plants using environmental data including shortwave radiation, temperature, precipitation, irrigation and ozone concentration. Leaf growth, dry matter accumulation, water budget, nitrogen input and seed growth linked to senescence and abscission of leaves are described in the model. The effects of ozone are modeled as reduced photosynthate production and accelerated senescence. The model was applied to the open-top chamber experiments in which soybean plants were exposed to ozone under two levels of soil moisture regimes. After calibrating the model to the growth data and seed yield, goodness-of-fit of the model was tested. The model fitted well for top dry weight in the vegetative growth phase and also at maturity. The effect of ozone on seen yield was also described satisfactorily by the model. The simulation showed apparent interaction between the effect of ozone and soil moisture stress on the seed yield. The model revealed that further work is needed concerning the effect of ozone on the senescence process and the consequences of alteration of canopy microclimate by the open-top chambers.     

Radish (Raphanus sativus L.): a model for studying plant responses to air pollutants and other environmental stresses

The use of Raphanus sativus L. as a model crop for studies on plant response to environmental stresses is reviewed with emphasis on the effects of different atmospheric pollutants (O(3), SO(2), NO(2), acidic precipitation) and their combinations. Responses to temperature, light supply, water stress, and atmospheric CO(2) are also studied and discussed. In addition, the references reviewed are evaluated in terms of their experimental protocols on growth conditions and recommendations for optimal ranges of environmental and cultural variables, i.e. light, temperature, nutrient supply are given. Its distinct pattern of biomass partitioning, the small dimensions along with short and easy culture make radish an excellent experimental plant. The fleshy below-ground storage organ, formed by the hypocotyl and upper radicle, acts as the major sink during vegetative development. Abundant assimilate supply due to elevated levels of CO(2) along with high irradiation frequently promote hypocotyl growth more than shoot growth, whereas under conditions of stress shoot growth is maintained at the expense of the hypocotyl. This makes the hypocotyl: shoot ratio of radish a very sensitive and suitable indicator for various environmental stresses. Potential weaknesses and shortcomings of radish in its role as a model crop, particularly the high variability of injury and growth responses, are discussed along with possible solutions. Future research needs are derived from the summarized results presented and from some disparities among findings within the literature reviewed.     

A Special Purpose Plant Environmental Chamber for Air Pollution Studies

The controlled atmosphere aspects of the environmental chambers at the University of Utah are described. Control of wind velocity, CO₂, concentration, temperature, relative humidity, and pollutant concentration are discussed. Requirements of our research program dictating the chamber design include: (1) ability to expose plants to air pollutants under the same environmental conditions at different times; (2) ability to simulate field environmental conditions within acceptable limits; (3) ability to study the effects of temperature, light, relative humidity, and wind velocity on response of plants to air pollutants; (4) ability to measure growth suppression, respiration, and transpiration; and (5) ability to measure the pollutant uptake rate of the plants.     

The impact of UV-B radiation and ozone on terrestrial vegetation

Although terrestrial vegetation has been exposed to UV-B radiation and ozone over the course of evolutionary history, it is essential to view the effects on vegetation of changing levels of these factors in the context of other features of climate change, such as increasing CO(2) levels and changes in temperature and precipitation patterns. Much of our understanding of the impacts of increased UV-B and ozone levels has come from studies of the effects of each individual factor. While such information may be relevant to a wider understanding of the roles that these factors may play in climate change, experience has shown that the interactions of environmental stresses on vegetation are rarely predictable. A further limitation on the applicability of such information results from the methodologies used for exposing plants to either factor. Much of our information comes from growth chamber, greenhouse or field studies using experimental protocols that made little or no provision for the stochastic nature of the changes in UV-B and ozone levels at the earth's surface, and hence excluded the roles of repair mechanisms. As a result, our knowledge of dose-response relationships under true field conditions is both limited and fragmentary, given the wide range of sensitivities among species and cultivars. Adverse effects of increased levels of either factor on vegetation are qualitatively well established, but the quantitative relationships are far from clear. In both cases, sensitivity varies with stage of plant development. At the population and community levels, differential responses of species to either factor has been shown to result in changes in competitiveness and community structure. At the mechanistic level, ozone generally inhibits photosynthetic gas exchange under both controlled and field conditions, and although UV-B is also inhibitory in some species under controlled conditions, others appear to be indifferent, particularly in the field. Both factors affect metabolism; a common response is increased secondary metabolism leading to the accumulation of phenolic compounds that, in the case of UV-B, offer the leaf cell some protection from radiation. Virtually no information is available about the effects of simultaneous or sequential exposures. Since both increased surface UV-B and ozone exposures have spatial and temporal components, it is important to evaluate the different scenarios that may occur, bearing in mind that elevated daytime ozone levels will attenuate the UV-B reaching the surface to some extent. The experimentation needed to acquire unequivocal effects data that are relevant to field situations must therefore be carried out using technologies and protocols that focus on quantification of the interactions of UV-B and ozone themselves and their interactions with other environmental factors.     

New approaches to study the relationship between stomatal conductance and environmental factors under Mediterranean climatic conditions

The most frequently models used (Ball–Berry and Jarvis-type models) to estimate stomatal conductance (Gs) values have limitations when applied to plants growing in Mediterranean climate. To overcome these limitations, several statistical methodologies (Multiple Linear Regression, Neural Net Analysis (NNA)) were used to build models to predict Gs. However, all these models were unable to integrate the physiological response of plants to the overall limiting environmental parameters in our Mediterranean site especially during the summer drought. With this in mind, it is relevant to find alternative approaches which link Gs response to environmental limitations of plants. In this paper, we demonstrate that: (1) the different linear and nonlinear statistical approaches used significantly affect the weights of the environmental variables which are utilized in semi-empirical Gs models; (2) a tight relationship exists between summer values of Gs and the rate of accumulated precipitations (α) in the first 5 months of the year, thus allowing to predict Gs in a quantitative way; and (3) the latter is also related to different water-use strategies adopted by plants in response to drought stress in the summer period. Because α is easily calculated, it is an interesting parameter for the Gs modelling addressed to understand many important aspects of the plant–environment interactions, such as water relations and pollutant uptake.