Reprint of: Photoperoxidation in Isolated Chloroplasts I. Kinetics and Stoichiometry of Fatty Acid Peroxidation.

A photo-induced cyclic peroxidation in isolated chloroplasts is described. In an osmotic buffered medium, chloroplasts upon illumination produce malondialdehyde (MDA)-a decomposition product of tri-unsaturated fatty acid hydroperoxides-bleach endogenous chlorophyll, and consume oxygen. These processes show (a) no reaction in the absence of illumination; (b) an initial lag phase upon illumination of 10-20 minutes duration; (c) a linear phase in which the rate is proportional to the square root of the light intensity; (d) cessation of reaction occurring within 3 minutes after illumination ceases; and (e) a termination phase after several hours of illumination. The kinetics of the above processes fit a cyclic peroxidation equation with velocity coefficients near those for chemical peroxidation. The stoichiometry of MDA/O2 = 0.02, and O2/Chlbleached = 6.9 correlates well with MDA production efficiency in other biological systems and with the molar ratio of unsaturated fatty acids to chlorophyll. The energies of activation for the lag and linear phases are 17 and 0 kcal/mole, respectively, the same as that for autoxidation. During the linear phase of oxygen uptake the dependence upon temperature and O2 concentration indicates that during the reaction, oxygen tension at the site of peroxidation is 100-fold lower than in the aqueous phase. It is concluded that isolated chloroplasts upon illumination can undergo a cyclic peroxidation initiated by the light absorbed by chlorophyll. Photoperoxidation results in a destruction of the chlorophyll and tri-unsaturated fatty acids of the chloroplast membranes.

Risk Communication Emergency Response Preparedness: Contextual Assessment of the Protective Action Decision Model.

Studies are continuously performed to improve risk communication campaign designs to better prepare residents to act in the safest manner during an emergency. To that end, this article investigates the predictive ability of the protective action decision model (PADM), which links environmental and social cues, predecision processes (attention, exposure, and comprehension), and risk decision perceptions (threat, alternative protective actions, and stakeholder norms) with protective action decision making. This current quasi-longitudinal study of residents (N = 400 for each year) in a high-risk (chemical release) petrochemical manufacturing community investigated whether PADM core risk perceptions predict protective action decision making. Telephone survey data collected at four intervals (1995, 1998, 2002, 2012) reveal that perceptions of protective actions and stakeholder norms, but not of threat, currently predict protective action decision making (intention to shelter in place). Of significance, rather than threat perceptions, perception of Wally Wise Guy (a spokes-character who advocates shelter in place) correlates with perceptions of protective action, stakeholder norms, and protective action decision making. Wally's response-efficacy advice predicts residents' behavioral intentions to shelter in place, thereby offering contextually sensitive support and refinement for PADM.

Chemical Manufacturing and Refining Industry Legitimacy: Reflective Management, Trust, Precrisis Communication to Achieve Community Efficacy.

Calls for emergency right-to-know in the 1980s, and, in the 1990s, risk management planning, motivated U.S. chemical manufacturing and refining industries to operationalize a three-pronged approach to risk minimization and communication: reflective management to increase legitimacy, operational safety programs to raise trust, and community engagement designed to facilitate citizens' emergency response efficacy. To assess these management, operational, and communication initiatives, communities (often through Local Emergency Planning Committees) monitored the impact of such programs. In 2012, the fourth phase of a quasi-longitudinal study was conducted to assess the effectiveness of operational change and community outreach in one bellwether community. This study focuses on legitimacy, trust, and response efficacy to suggest that an industry can earn legitimacy credits by raising its safety and environmental impact standards, by building trust via that change, and by communicating emergency response messages to near residents to raise their response efficacy. As part of its campaign to demonstrate its concern for community safety through research, planning, and implementation of safe operations and viable emergency response systems, this industry uses a simple narrative of risk/emergency response-shelter-in-place-communicated by a spokes-character: Wally Wise Guy.

Image analysis of epicuticular damage to foliage caused by dry deposition of the air pollutant nitric acid.

Nitric acid vapor is produced by the same photochemical processes that produce ozone. In the laboratory, concentrated nitric acid is a strong acid and a powerful oxidant. In the environment, where the concentrations are much lower, it is an innocuous source of plant nitrogen. As an air pollutant, which mode of action does dry deposition of nitric acid follow? We investigated the effects of dry deposition of nitric acid on the foliage of four tree species native to the western United States. A novel controlled environment, fumigation system enabled a four-week exposure at concentrations consistent with ambient diurnal patterns. Scanning electron microscopy and automated image analysis revealed changes in the epicuticular wax layer during fumigation. Exposure to nitric acid resulted in a reproducible suite of damage symptoms that increased with increasing dose. Each tree species tested exhibited a unique set of damage features, including cracks, lesions, and conformation changes to epicuticular crystallite structures. Dry deposition of atmospheric nitric acid caused substantial perturbation to the epicuticular surface of all four tree species investigated, consistent with the chemical oxidation of epicuticular waxes. Automated image analysis eliminated many biases that can trouble microscopy studies. Trade names and commercial enterprises or products are mentioned solely for information. No endorsements by the U.S. Department of Agriculture are implied.

Foliar loading and metabolic assimilation of dry deposited nitric acid air pollutants by trees.

Dry deposition of nitric acid vapor (HNO(3)) is a major contributor to eutrophication of natural ecosystems. Although soil fertilization by nitrogen deposition is considered to be the primary pathway for changes in plant nutrient status and shifts in ecological structure, the aerial portion of plants offer many times the surface area in which to collect atmospheric HNO(3). As much as 60% of deposited nitrogen may be retained in the canopy and not land on the soil surface below. Although uptake and assimilation appears to contribute to retention, only a small percentage of dry deposition is recovered in assimilated N pools. To test the importance of biological activity on the process and measurements of dry deposition, we used controlled environmental chambers to compare deposition to living and freeze-dried foliage of four tree species using (15)N-labeled HNO(3). In living trees, assimilation was determined by (15)N incorporation into free amino acids and proteins in leaves and roots. From 10% to 60% of the retained HNO(3) was incorporated into the biologically active nitrogen pool. The remainder was bound to foliar surfaces in an insoluble form in either living or freeze-dried foliage. The importance of the boundary layer conditions emerged as a primary factor controlling dry deposition characteristics and measurements.Trade names and commercial enterprises or products are mentioned solely for information. No endorsements by the U.S. Department of Agriculture are implied.

Modification of the biochemical pathways of plants induced by ozone: what are the varied routes to change?

When plants are observed under a low dose of ozone, some physiological and metabolic shifts occur. Barring extreme injury such as tissue damage or stomata closure, most of these disruptive changes are likely to have been initiated at the level of gene expression. The belief is oxidative products formed in ozone exposed leaves, e.g. hydrogen peroxide, are responsible for much of the biochemical adjustments. The first line of defense is a range of antioxidants, such as ascorbate and glutathione, but if this defense is overwhelmed, subsequent actions occur, similar to systemic acquired resistance or general wounding. Yet there are seemingly unrelated metabolic responses which are also triggered, such as early senescence. We discuss here the current understanding of gene control and signal transduction/control in order to increase our comprehension of how ozone alters the basic metabolism of plants and how plants counteract or cope with ozone.

Alterations of the biochemical pathways of plants by the air pollutant ozone: which are the true gauges of injury?

Plant strategies to survive ozone stress include exclusion or tolerance of ozone. If these processes fail, past observations of ozone injury have indicated many physiological and metabolic changes then occur; most of these changes are likely to have been initiated at the level of gene expression, suggesting signal transduction. In the last decade considerable understanding of the biochemical process within plants has been developed. Currently there are several hypotheses regarding a response of plants to ozone fumigation: [1] membrane dysfunction and alteration of purpose; [2] stress ethylene interactions; [3] impairment of photosynthesis via changes in Rubisco levels and the guard cells so that the stomata do not track correctly the environment; [4] antioxidant protection through metabolites and enzyme systems to reduce the oxidant load; and [5] general impairment or disruption of metabolic pathways. Many believe that free radicals and other oxidative products, formed in plant leaves under ozone exposure, are responsible for much of the spread of the biochemical alterations. There are obvious chemicals that may account for the changes that are observed, such as hydrogen peroxide. Once the ozone enters the tissue, evidence suggests the first line of defense is a range of antioxidants, such as ascorbate, glutathione peroxidase, superoxide dismutase, and catalase. If overwhelmed, subsequent events occur which are highly suggestive of systemic acquired resistance. Furthermore, other defensive indicators, such as salicylic acid and jasmonic acid, tend to increase, but more slowly than ethylene, and spread their signaling effects more widely in the plant. The primary set of metabolic reactions that ozone triggers is thought to be "wounding" responses with a secondary response of senescence. The dramatic strides in understanding the genetic make-up of plants, gene control, and signal transduction/control over the last few years will only accelerate in the future. We need now to have an understanding of those events that can be translated into more detailed schemes of how ozone alters much of the basic metabolism of plants and how plants counteract or cope with ozone. What is now known about how varied biochemicals and their pathways are changed upon ozone exposure will be discussed.

Chronic vs. short-term acute O3 exposure effects on nocturnal transpiration in two Californian oaks.

We tested the effect of daytime chronic moderate ozone (O3) exposure, short-term acute exposure, and both chronic and acute O3 exposure combined on nocturnal transpiration in California black oak and blue oak seedlings. Chronic O3 exposure (70 ppb for 8 h/day) was implemented in open-top chambers for either 1 month (California black oak) or 2 months (blue oak). Acute O3 exposure (approximately 1 h in duration during the day, 120-220 ppb) was implemented in a novel gas exchange system that supplied and maintained known O3 concentrations to a leaf cuvette. When exposed to chronic daytime O3 exposure, both oaks exhibited increased nocturnal transpiration (without concurrent O3 exposure) relative to unexposed control leaves (1.8x and 1.6x, black and blue oak, respectively). Short-term acute and chronic O3 exposure did not further increase nocturnal transpiration in either species. In blue oak previously unexposed to O3, short-term acute O3 exposure significantly enhanced nocturnal transpiration (2.0x) relative to leaves unexposed to O3. California black oak was unresponsive to (only) short-term acute O3 exposure. Daytime chronic and/or acute O3 exposures can increase foliar water loss at night in deciduous oak seedlings.

Responses to ozone of varieties of common bean (Phaseolus vulgar is L.).

Varying modes of ozone sensitivity were detected in 12 varieties of Phaseolus vulgaris. Seedlings were exposed to 0.4-0.5 µl 1-1 ozone for 75-135 min in growth chambers, until the most sensitive variety manifested visible damage at the leaf margins. Sensitive varieties showed ozone-induced chlorophyll loss and/or inhibition of photosynthesis. A set of physiological characters thought to mediate ozone response was also assayed in control and fumigated plants: stomatal conductance, the regulator of ozone entry into the leaf; glutathione (as non-protein sulphydryl) and ascorbate, the antioxidants; and polyphenol oxidase activity, a measure of the wound response. Some ozone-tolerant varieties appeared to lower chlorophyll loss solely by blocking ozone entry through decreased stomatal conductances, whereas other ozone-tolerant varieties appeared to mitigate ozone damage through the action of the antioxidants, ascorbate, and non-protein sulphydryl. Similarly, ozone-sensitive varieties showed possible alternative mechanisms of sensitivity. Damage appeared to derive from either comparatively high stomatal conductances, or comparatively low levels of antioxidants in spite of low stomatal conductances. Only one variety showed elevated photosynthesis rates in response to ozone, indicating a potential to repair ozone damage. Elevated ascorbate concentrations appeared to protect some varieties from post-fumigation depressions in photosynthesis. The results were inconclusive regarding the role of polyphenol oxidase as the wound response.

Extreme Toxicity of Ethanol During Activation of Sea Urchin Eggs: (ethanol toxicity/ionophore A23187/parthenogenesis/Strongylocentrotus purpuratus/K+ -permeability).

We have examined the effects of ethanol on early fertilization events and later development in the sea urchin Strongylocentrotus purpuratus. Eggs can still be fertilized in ethanol concentrations as high as 480 mM (2.0%); egg cytolysis was rapidly observed postinsemination in 50% of the cells at 220 mM ethanol. Yet, sperm motility was essentially normal in 250 mM ethanol; 940 mM ethanol was required to affect a 50% reduction. To determine the effect of ethanol on K+ -efflux from eggs induced by fertilization, we used parthenogenetic activation induced by the Ca2+ -ionophore A23187. Surprisingly, ethanol at only 0.2 mM caused an abnormal K+ -efflux, but only when added between 1 and 3 min after induction of activation. The K+ -efflux rates of unfertilized eggs were not influenced by up to 730 mM ethanol. Finally, normal embryonic development through the mesenchyme blastula stage was observed in egg suspensions which were treated for 30 min with ethanol concentrations as high as 240 mM, but washed with normal seawater prior to insemination. Normal plutei were obtained from cultures which were continuously cultured in 24 mM ethanol from 15 min postinsemination. We conclude that an extreme ethanol sensitivity of embryogenesis is apparent only during the cortical reaction.