Development Of Visible Injury Research Articles

Global identification of potential gene biomarkers associated with ozone-induced foliar injury in rice seedling leaves by correlating their symptom severity with transcriptome profiling

A combined approach of evaluating ozone (O3)-caused foliar injury symptom and global gene expression profiling was used to identify potential genes associated with severity of injury on leaves of O3 (200 ppb)-fumigated (1, 12, 24, 48, and 72 h) two-week-old rice (cv. Nipponbare) seedling. Foliar injuries were evaluated up to 72 h using both qualitative visual scale and quantitative RGB (red-green-blue) image analysis methods. The (R-G)/(R+G) was an optimal quantitative RGB parameter to assess foliar injury. Large-scale transcript profiling of leaves identified 270 genes linked with foliar injury. Genes were subjected to Pearson’s correlation test between their expression changes and O3-induced foliar injury changes (relative (R-G)/(R+G) parameters). Expression of 146 genes was found to increase with increased foliar severity up to 72 h, showing a positive, tight correlation between a subset of gene expression and commonly observed O3-triggerred symptom of foliar injury with correlation coefficient below -0.80. Of 146 genes, genes involved in metabolism (25%) formed a major functional category. Metabolic networks with identified metabolic genes provided insight into cellular responses such as photorespiration, biosynthesis of secondary metabolites, and detoxification. The O3 effect on these cellular responses has been previously reported based on physiological and biochemical studies, validating our approach used in this study to globally identify O3-responsive biomarkers tightly linked with foliar injury symptom. This study provides evidence for presence of large number of genes associated with foliar injury symptom than thought before, serving as a resource of potential biomarkers to study mechanisms of visible injury development by O3.DOI: http://dx.doi.org/10.3126/ijls.v6i1.6059

Foliar, Physiologial and Growth Responses of Four Maple Species Exposed to Ozone

The effects of ozone in four maple species, Acer campestre, A. opalus subsp. granatense, A. monspessulanum and A. pseudoplatanus were studied in OTC under two different experimental conditions: in charcoal filtered air (CF), and in non filtered air plus 30 ppb ozone (NF+30). The four species of maple showed contrasting sensitivity to ozone as demonstrated by visible injury development, gas exchange and chlorophyll a fluorescence, and growth measurements. Plant injury index (i.e. a combination of percentage of injured leaves and leaf surface affected) was more consistently related with physiological measurements than the onset of first symptom of visible injury. Differences in ozone sensitivity among species may be partly related to higher stomatal conductances in A. opalus and A. pseudoplatanus. In these two species, ozone produced significant reductions in CO2 assimilation under saturating light conditions (Asat), stomatal conductance (gs), transpiration rate (Tr) and Water Use Efficiency (WUE) (the latter also significantly declined in A. campestre) towards the end of summer, while intercellular CO2 concentrations (Ci) increased significantly. In asymptomatic leaves of A. opalus, neither stomatal limitation nor photoinhibitory damage (Fv/Fm) could explain the observed decline of Asat, and photosynthesis was down regulated by reducing the proportion of absorbed energy used in photochemistry (ΦPSII) at expenses of the energy dispersed non-photochemically (NPQ). Leaf N content also declined significantly in A. pseudoplatanus. Plants exposed to ozone showed a tendency to decrease growth, but it was not significant within the exposure period for any of the four species. The most sensitive species were A. opalus and A. pseudoplatanus, while the species with the smallest and more coriaceous leaves, A. monspessulanum, was the most resistant.

The Relative Sensitivity of Different Mediterranean Plant Species to Ozone Exposure

An experimental study was performed in open-top chambers to assess the relative O3-sensitivity of the following Mediterranean woody plants: Quercus ilex ssp. ilex, Quercus ilex ssp. ballota, Olea europaea ssp. sylvestris, Ceratonia siliqua and Arbutus unedo. Assessment of O3 ‘sensitivity’ was based on the development of O3-induced visible injury and the extent of the reduction in relative growth rate induced by O3. Two-year-old seedlings were exposed in open-top chambers to charcoal filtered air (CFA), Non-filtered air (NFA) or Non-filtered air supplied with 40 ppb O3 from 09:00 to 18:00 hours (NFA+40). No clear relationships were found between the development of visible injury and effects on plant growth or accumulated biomass. Olea europea ssp. sylvestris and Quercus ilex ssp. ballota appeared to be the most O3-sensitive tree species screened; a ten month exposure to ambient O3 levels (AOT40 = 12.4 ppm.h) caused reductions in height and/or stem growth. Further research is needed to characterise the physiological, biochemical and anatomical characteristics that may underlie the ‘sensitivity’ of certain Mediterranean species to O3

Investigating microclimatic influences on ozone injury in clover (Trifolium subterraneum) using artificial neural networks

summaryMicroclimatic factors interact during ozone episodes to influence the sensitivity of plants to ozone and thus are likely Co modify the amount of injury development. This paper investigates these interactions in an ozone‐sensitive cultivar of clover (Trifolium subterraneum cv. Geraldton). Experiments were conducted using a glasshouse‐based closed‐chamber exposure system in which the plants were exposed for 7 h to either charcoal‐filtered air (CF) or CF plus ozone at concentrations ranging from 40 to 160 ppb. The microclimatic conditions inside the chambers ranged from 16 to 36 C, 0‐9‐3‐6 kPa vapour pressure deficit (VPD), and 80–460 μmol m−2s−1Photosynthetically Active Radiation (PAR). Seven days after ozone exposure, the extent of foliar ozone injury was scored visually. The assessment scoring system was validated by pigment analysis. The data from these exposures were analysed using artificial neural networks (ANNs), the principles of which are described in the paper. Two ANNs were used, one to investigate the effects of microclimate on the threshold AOT40 (dose accumulated above a threshold of 40 ppb) above which injury developed, the other to determine the extent of visible injury development. Both networks used temperature. VPD, PAR and AOT40 as inputs. Testing with previously unseen data showed that the networks produced accurate predictions of the threshold and extent of injury for a range of ozone doses and microclimatic conditions. For example, the injury score network predicted that at 100 μmol m2s1PAR and 1 kPa VPD an AOT40 of 150 ppb h was required to produce an injury score of 1, whereas in conditions of 400 μmol m−2s−1s′ PAR and 3.5 kPa VPD, an AOT40 of 460 ppb h was required. Analysis of the weightings of components of the trained networks indicated that VPD and PAR had a stronger influence on the response to ozone than did temperature. Furthermore, this approach revealed that microclimate had a greater influence on the extent of ozone injury than on the threshold for injury.

The effect of the exclusion of dry and wet deposition on visible symptoms and accumulation of sulphur and fluoride by Picea abies needles near point‐sources

The effect of air pollutants on conifers was studied throughout the year near industrial point‐sources using two types of half‐open chambers for excluding wet or dry deposition around selected trees. Results indicate that pollutant uptake from dry deposition and wash‐off effect by rain have overriding influence in the internal accumulation of pollutants by needles. The exclusion of wet deposition substantially enhanced pollutant accumulation in the needles and suggests that wet deposition itself has a minor direct effect on accumulation near point‐sources. Near the fertilizer plant the trees growing in filtered air exhibited fewer visible symptoms and had lower accumulations of fluoride. This suggests that decreasing the gaseous air pollutants would improve the condition of conifers at this site. Results suggest also that besides high needle pollutant content, winter conditions are needed to facilitate visible injury development.

Effects of simulated acid fog on leaf acidification and injury development of pinto beans

Pinto beans (Phaseolus vulgaris L. cv. UI 111) were exposed for 8 h to simulated fog solutions made up of 2:1 nitric acid: sulfuric acid plus background ions, acidified to pH 3.2, 2.8, 2.4, and 2.0. Rate of fog deposition was ca. 1 mm h−1. Examination of visible foliar injury development, scanning electron microscopy (SEM) examination, and measurement of leaf extract pH were performed every 2 h. Both visual and SEM observations during exposure showed no change in leaf surface characteristics for plants exposed to pH 3.2 and 2.8 fog solutions but 1 week after pH 2.8 exposures, injury was seen on primary leaves and young trifoliate leaves. The first indications of injury at pH 2.4 were seen under SEM after 8 h of exposure. Foliar injury was apparent after only 2 h of exposure at pH 2.0 and severe acid necrosis developed after 24 h. Changes in acidity of leaf extracts were closely correlated with subsequent injury development. No changes were observed in extracts of plants exposed to pH 3.2 simulated fog compared with controls. After 8 h of exposure, leaf extracts of plants exposed to pH 2.8 fog had dropped 0.05 pH units. Plants exposed to pH 2.4 and pH 2.0 for 8 h had leaf extracts that were 0.12 and 0.18 pH units lower, respectively. Comparison of the three measured parameters of acid fog effects (visible injury development, SEM examination of leaf surfaces, and determination of leaf extract pH) showed extract pH to be a simple, quantifiable, and sensitive indicator of the negative effects of acid precipitation on plants.

Ozone Suppression of White Pine Net Photosynthesis

Reduction in rates of net photosynthesis following exposure to ozone was observed in eastern white pine saplings prior to the development of visible injury. Branches exposed to consecutive doses of 50-80 pphM ozone for 4 hr and 80-90 pphM ozone for 3 hr appeared to have suppressed net photosynthetic rates but results were confounded by diurnal rate variation. Photosynthetic rates of treated branches returned to normal levels following this initial ozone exposure. A second ozonation involving dosages of 90-100 pphM for 5 and 3 hr was sufficient to reduce rates of net photosynthesis by approximately 80%. 13 references, 1 figure.

Effect of Ozone and Ozonated 1-hexene on Respiration and Photosynthesis of Leaves.

The treatment of Pinto bean leaves with either ozone or ozonated hexene gas in air caused a rise in the respiration rate up to more than four times that of untreated control leaves. Plant responses to the two gases were similar. The rate of photosynthesis of treated bean leaves was less than that of controls. Both the amounts of stimulation of respiration and the inhibition of photosynthesis were directly related to the development of visible injury symptoms in certain tissues of the bean leaves. No stimulation of bean leaf respiration or inhibition of photosynthesis occurred unless visible injury developed. However, ozone caused a rise in the respiration rate of Valencia orange leaves with no concomitant development of visible injury. Citrus leaves gave no response until ozone concentrations approached those required to produce visible injury symptoms. Treatment with ozonated hexene at concentrations eliciting changes in respiration and photosynthesis in bean leaves caused no change in these processes in citrus leaves. A comparison of ozone- and ozonated hexene-treated bean leaves showed that the respiratory quotients were not different from that of the control leaves. 9 references, 3 figures, 2 tables.