Foliar Injury Research Articles

Responses of Growth, Oxidative Injury and Chloroplast Ultrastructure in Leaves of Lolium perenne and Festuca arundinacea to Elevated O3 Concentrations.

The effects of increasing atmospheric ozone (O3) concentrations on cool-season plant species have been well studied, but little is known about the physiological responses of cool-season turfgrass species such as Lolium perenne and Festuca arundinacea exposed to short-term acute pollution with elevated O3 concentrations (80 ppb and 160 ppb, 9 h d−1) for 14 days, which are widely planted in urban areas of Northern China. The current study aimed to investigate and compare O3 sensitivity and differential changes in growth, oxidative injury, antioxidative enzyme activities, and chloroplast ultrastructure between the two turf-type plant species. The results showed that O3 decreased significantly biomass regardless of plant species. Under 160 ppb O3, total biomass of L. perenne and F. arundinacea significantly decreased by 55.3% and 47.8% (p < 0.05), respectively. No significant changes were found in visible injury and photosynthetic pigment contents in leaves of the two grass species exposed to 80 ppb O3, except for 160 ppb O3. However, both 80 ppb and 160 ppb O3 exposure induced heavily oxidative stress by high accumulation of malondialdehyde and reactive oxygen species in leaves and damage in chloroplast ultrastructure regardless of plant species. Elevated O3 concentration (80 ppb) increased significantly the activities of superoxide dismutase, catalase and peroxidaseby 77.8%, 1.14-foil and 34.3% in L. perenne leaves, and 19.2%, 78.4% and 1.72-fold in F. arundinacea leaves, respectively. These results showed that F. arundinacea showed higher O3 tolerance than L. perenne. The damage extent by elevated O3 concentrations could be underestimated only by evaluating foliar injury or chlorophyll content without considering the internal physiological changes, especially in chloroplast ultrastructure and ROS accumulation.

Sweetpotato tolerance and Palmer amaranth control with indaziflam

AbstractField studies were conducted in North Carolina in 2018 and 2019 to determine sweetpotato tolerance to indaziflam and its effectiveness in controlling Palmer amaranth in sweetpotato. Treatments included indaziflam pre-transplant; 7 d after transplanting (DATr) or 14 DATr at 29, 44, 58, or 73 g ai ha−1; and checks (weedy and weed-free). Indaziflam applied postemergence caused transient foliar injury to sweetpotato. Indaziflam pretransplant caused less injury to sweetpotato than other application timings regardless of rate. Palmer amaranth control was greatest when indaziflam was applied pretransplant or 7 DATr. In a weed-free environment, sweetpotato marketable yield decreased as indaziflam application was delayed. No differences in storage root length to width ratio were observed.

Black Pecan Aphid (Hemiptera: Aphididae) Management on Pecan When Gibberellic Acid Is Applied Concurrently With Broad-Spectrum Insecticides.

Aphids (Hemiptera: Aphididae) are serious pests of pecan foliage (Carya illinoinensis [Wangenh.] K. Koch). The black pecan aphid, Melanocallis caryaefoliae (Davis) (Hemiptera: Aphididae), feeds on pecan foliage and elicits leaf chlorosis that can cause defoliation. In contrast, the blackmargined aphid, Monellia caryella (Fitch) (Hemiptera: Aphididae), and yellow pecan aphid, Monelliopsis pecanis Bissell (Hemiptera: Aphididae), feed on pecan foliage but do not elicit chlorotic feeding injury. Application of gibberellic acid (GA3) to pecan foliage reduces chlorotic foliar injury and nymphal populations of the black pecan aphid. GA3 has potential to manage black pecan aphid later in the season when broad-spectrum insecticides are used to control direct pests of pecan nuts but also inadvertently induce aphid outbreaks. Here, broad-spectrum insecticides were used with GA3 or aphicides in orchard trials for 2 yr. Populations of aphids and natural enemies along with chlorotic feeding injury on foliage were assessed. When used concurrently with GA3 or aphicides, broad-spectrum insecticides did not flare black pecan aphid populations. However, combined populations blackmargined aphids and yellow pecan aphids were higher in treatments with GA3 than with an aphicide or in the control treatment during one of two years. Application of GA3 or the aphicide often led to significantly less chlorotic injury than observed in the control. Surprisingly, natural enemies were not significantly affected by broad-spectrum insecticides when applied concurrently with GA3. These results show that GA3 can be used as part of a late-season IPM strategy to protect foliage from localized chlorotic leaf injury elicited by the black pecan aphid.

Spraying high concentrations of chelated zinc enhances zinc biofortification in wheat grain.

Foliar application of highly concentrated ZnSO4 fertilizer improves Zn biofortification in wheat grains. However, excess ZnSO4 ·7H2 O concentration (≥5g kg-1 , w v-1 ) has been associated with leaf burn and yield loss, necessitating Zn sources with a high threshold concentration. The aim of this study, based on a 2 year field experiment conducted on wheat cultivated in acidic and alkaline soil, was to identify a suitable Zn formulation with a high Zn concentration or efficient adjuvant to achieve optimal Zn biofortification levels without compromising agronomic performance. There was a continued increase in the Zn concentration in wheat grains and a decrease in grain yield with an increase in the concentration of the Zn foliar sprays in both soil types examined. Wheats treated with chelated Zn foliar sprays - Zn glycine chelate (ZnGly) and Zn-ethylenediaminetetraacetic acid (ZnEDTA) - had less foliar injury than those treated with unchelated Zn fertilizers. Furthermore, irrespective of wheat cultivars and soil types, ZnEDTA applied to wheat at a concentration of 10g kg-1 achieved the highest grain Zn concentration without negatively affecting the wheat performance. Adjuvant type and concentration caused no significant variation in grain Zn concentration. Overall, without foliar burn, wheat treated with 10g kg-1 ZnEDTA foliar spray had the best performance with regard to grain Zn concentration and grain yield, which could have considerable implications for Zn biofortification of wheat grain. © 2021 Society of Chemical Industry.

A growth and biochemistry of ten high yielding genotypes of Pakistani rice (Oryza sativa L.) at maturity under elevated tropospheric ozone

Experimental studies were conducted to estimate the possible damage caused to ten rice (Oryza sativa L.) genotypes of Pakistan by tropospheric ozone. The experimental site is located at 31.4504° N and 73.1350° E, at an altitude of 184 m.a.s level with an average annual rainfall of 784 mm. A suitable and agile method was adopted to assess tolerance and susceptibility in rice genotypes at an early growth stage. Genotype Injury response, growth and biochemical parameters were measured to estimate possible effects of ozone, which was subsequently proclaimed as a criterion for ozone tolerance. Rice genotypes were subjected to ozone concentrations of 70 pbb (Current ambient) and 120 pbb (expected in near future) under a polytunnel. The findings indicated that ozone, an atmospheric pollutant, substantially harmed crop growth and metabolism, as well as inflicted a specific type of foliar injury that caused early leaf senescence. Rice genotype IR-9 followed by Punjab-Basmati and Ksk-434 appeared to be the most susceptible, whereas Basmati-515 followed by Basmati 2000 and super-Basmati were found to be Ozone-tolerant. Plant genotypes grown under elevated ozone showed 13.45% and 11.35% reduction in total root and shoot dry weight, and 25.54% and 6.6% decrease in plant leaf area and plant total length respectively compared to the control group. A significant interaction between treatment × chemical components and growth parameters was also found. The Present study confirms a direct relationship between visual response and growth as well as biochemical parameters. Declared results were statistically analyzed by using analysis of variance at confidence level of p < 0.05.

Tree crown injury from wildland fires: causes, measurement and ecological and physiological consequences.

SummaryThe dead foliage of scorched crowns is one of the most conspicuous signatures of wildland fires. Globally, crown scorch from fires in savannas, woodlands and forests causes tree stress and death across diverse taxa. The term crown scorch, however, is inconsistently and ambiguously defined in the literature, causing confusion and conflicting interpretation of results. Furthermore, the underlying mechanisms causing foliage death from fire are poorly understood. The consequences of crown scorch – alterations in physiological, biogeochemical and ecological processes and ecosystem recovery pathways – remain largely unexamined. Most research on the topic assumes the mechanism of leaf and bud death is exposure to lethal air temperatures, with few direct measurements of lethal heating thresholds. Notable information gaps include how energy transfer injures and kills leaves and buds, how nutrients, carbohydrates, and hormones respond, and what physiological consequences lead to mortality. We clarify definitions to encourage use of unified terminology for foliage and bud necrosis resulting from fire. We review the current understanding of the physical mechanisms driving foliar injury, discuss the physiological responses, and explore novel ecological consequences of crown injury from fire. From these elements, we propose research needs for the increasingly interdisciplinary study of fire effects.

Stress markers and physiochemical responses of the Mediterranean shrub Phillyrea angustifolia under current and future drought and ozone scenarios

Mediterranean plants are particularly threatened by the exacerbation of prolonged periods of summer drought and increasing concentrations of ground-level ozone (O3). The aims of the present study were to (i) test if selected markers (i.e., reactive oxygen species, ROS; malondialdehyde, MDA; photosynthetic pigments) are able to discriminate the oxidative pressure due to single and combined stress conditions, and (ii) elucidate the physiochemical adjustments adopted by Phillyrea angustifolia (evergreen woody species representative of the maquis, also known as narrow-leaved mock privet) to perceive and counter to drought and/or O3. Plants were grown from May to October under the combination of two levels of water irrigation [i.e., well-watered (WW) and water-stressed (WS)] and three levels of O3 [i.e., 1.0, 1.5 and 2.0 times the ambient air concentrations, i.e. AA (current O3 scenario), 1.5 × AA and 2.0 × AA (future O3 scenarios), respectively], using a new-generation O3 Free Air Controlled Exposure (FACE) system. Overall, this species appeared relatively sensitive to drought (e.g., net CO2 assimilation rate and stomatal conductance significantly decreased, as well as total chlorophyll and carotenoid contents), and tolerant to O3 (e.g., as confirmed by the absence of visible foliar injury, the unchanged values of total carotenoids, and the detrimental effects on stomatal conductance, total chlorophylls and terpene emission only under elevated O3 concentrations). The combination of both stressors led to harsher oxidative stress. Only when evaluated together (i.e., combining the information provided by the analysis of each stress marker), ROS, MDA and photosynthetic pigments, were suitable stress markers to discriminate the differential oxidative stress induced by drought and increasing O3 concentrations applied singly or in combination: (i) all these stress markers were affected under drought per se; (ii) hydrogen peroxide (H2O2) and MDA increased under O3per se, following the gradient of O3 concentrations (H2O2: about 2- and 4-fold higher; MDA: +22 and + 91%; in 1.5 × AA_WW and 2.0 × AA_WW, respectively); (iii) joining together the ROS it was possible to report harsher effects under 2.0 × AA_WS and 1.5 × AA_WS (both anion superoxide and H2O2 increased) than under 2.0 × AA_WW (only H2O2 increased); and (iv) MDA showed harsher effects under 2.0 × AA_WS than under 1.5 × AA_WS (increased by 49 and 18%, respectively). Plants activated physiological and biochemical adjustments in order to partially avoid (e.g., stomatal closure) and tolerate (e.g., increased terpene emission) the effects of drought when combined with increasing O3 concentrations, suggesting that the water use strategy (isohydric) and the sclerophyllous habit can further increase the plant tolerance to environmental constraints in the Mediterranean area.

Ethylenediurea (EDU) effects on hybrid larch saplings exposed to ambient or elevated ozone over three growing seasons

Ground-level ozone (O3) pollution is a persistent environmental issue that can lead to adverse effects on trees and wood production, thus indicating a need for forestry interventions to mediate O3 effects. We treated hybrid larch (Larix gmelinii var. japonica × L. kaempferi) saplings grown in nutrient-poor soils with 0 or 400 mg L−1 water solutions of the antiozonant ethylenediurea (EDU0, EDU400) and exposed them to ambient O3 (AOZ; 08:00 − 18:00 ≈ 30 nmol mol−1) or elevated O3 (EOZ; 08:00 − 18:00 ≈ 60 nmol mol−1) over three growing seasons. We found that EDU400 protected saplings against most effects of EOZ, which included extensive visible foliar injury, premature senescence, decreased photosynthetic pigment contents and altered balance between pigments, suppressed gas exchange and biomass production, and impaired leaf litter decay. While EOZ had limited effects on plant growth (suppressed stem diameter), it decreased the total number of buds per plant, an effect that was not observed in the first growing season. These results indicate that responses to EOZ might have implications to plant competitiveness, in the long term, as a result of decreased potential for vegetative growth. However, when buds were standardized per unit of branches biomass, EOZ significantly increased the number of buds per unit of biomass, suggesting a potentially increased investment to bud development, in an effort to enhance growth potential and competitiveness in the next growing season. EDU400 minimized most of these effects of EOZ, significantly enhancing plant health under O3-induced stress. The effect of EDU was attributed mainly to a biochemical mode of action. Therefore, hybrid larch, which is superior to its parents, can be significantly improved by EDU under long-term elevated O3 exposure, providing a perspective for enhancing afforestation practices.

Safety and efficacy of linuron with or without an adjuvant or S-metolachlor for POST control of Palmer amaranth (Amaranthus palmeri) in sweetpotato

AbstractField studies were conducted to evaluate linuron for POST control of Palmer amaranth in sweetpotato to minimize reliance on protoporphyrinogen oxidase (PPO)-inhibiting herbicides. Treatments were arranged in a two by four factorial in which the first factor consisted of two rates of linuron (420 and 700 g ai ha−1), and the second factor consisted of linuron applied alone or in combinations of linuron plus a nonionic surfactant (NIS; 0.5% vol/vol), linuron plus S-metolachlor (800 g ai ha−1), or linuron plus NIS plus S-metolachlor. In addition, S-metolachlor alone and nontreated weedy and weed-free checks were included for comparison. Treatments were applied to ‘Covington’ sweetpotato 8 d after transplanting (DAP). S-metolachlor alone provided poor Palmer amaranth control because emergence had occurred at applications. All treatments that included linuron resulted in at least 98% and 91% Palmer amaranth control 1 and 2 wk after treatment (WAT), respectively. Including NIS with linuron did not increase Palmer amaranth control compared to linuron alone, but it resulted in greater sweetpotato injury and subsequently decreased total sweetpotato yield by 25%. Including S-metolachlor with linuron resulted in the greatest Palmer amaranth control 4 WAT, but increased crop foliar injury to 36% 1 WAT compared to 17% foliar injury from linuron alone. Marketable and total sweetpotato yields were similar between linuron alone and linuron plus S-metolachlor or S-metolachlor plus NIS treatments, though all treatments resulted in at least 39% less total yield than the weed-free check resulting from herbicide injury and/or Palmer amaranth competition. Because of the excellent POST Palmer amaranth control from linuron 1 WAT, a system that includes linuron applied 7 DAP followed by S-metolachlor applied 14 DAP could help to extend residual Palmer amaranth control further into the critical period of weed control while minimizing sweetpotato injury.

Rice response to sublethal rates of paraquat, metribuzin, fomesafen, and cloransulam-methyl at different application timings

AbstractThe application of paraquat mixtures with residual herbicides before planting rice is a common treatment in Mississippi, and rice in proximity is susceptible to off-target movement of these applications. Four concurrent studies were conducted in Stoneville, MS, to characterize rice performance following exposure to a sublethal rate of paraquat, metribuzin, fomesafen, and cloransulam-methyl at different application timings. Herbicides were applied to rice at the growth stages of spiking to one-leaf (VEPOST), two- to three-leaf (EPOST), three- to four-leaf (MPOST), 7 d postflood (PFLD), and panicle differentiation (PD). Regardless of application timing, rice injury following exposure to paraquat was ≥45%. Delays in maturity were increased by 0.3 d d−1 following paraquat from emergence through PD. Dry weight, rough rice yield, panicle density, and germination were reduced by 18.7 g, 131.5 kg ha−1, 5.6 m−2, and 0.3%, respectively, per day from application of paraquat at emergence through PD. By 28 d after treatment (DAT), metribuzin injured rice 3% to 6%, and that injury did not translate into a yield reduction. Regardless of application timing, rice injury following fomesafen application ranged from 2% to 5% 28 DAT. Rice exposed to cloransulam-methyl EPOST exhibited the greatest root and foliar injury 21 DAT and 28 DAT, respectively. Additionally, when rice was exposed to cloransulam-methyl EPOST, yield was reduced to 6,540 kg ha−1 compared with a yield of 7,850 kg ha−1 from nontreated rice. Rice yield was negatively affected after paraquat was applied any time after rice emergence. However, applications of paraquat to rice at early reproductive growth stages reduced rough rice yield and seed germination the greatest. Application timing is crucial in determining severity of rice injury. Early-season injury to rice following paraquat application had less effect on yield compared with injury at later stages. Additionally, fields devoted to seed rice production are at risk for reduced seed germination if they are exposed to paraquat during early reproductive growth stages.

IMPLEMENTATION OF MODERN TECHNOLOGIES TO ALLEVIATE

Introduction. Urban perennial plantations are exposed to numerous anthropogenic pollutants, recreational load, etc. As a result, the physical and chemical properties of the soil deteriorate, the development of useful soil microflora is inhibited, the phytosanitary properties of soil ecosystems worsen, the intensity of mineralization processes and availability of macro- and micronutrients for plants drops down, and the concentration of toxic substances increases, which leads to soil sickness. Problem Statement. Today, in Ukraine, the causes and features of soil sickness manifestation in urban ecosystems have been virtually unexplored, and there has been no environmentally sound approach to overcoming negative consequences of this phenomenon. Purpose. To implement environmentally sound technology for overcoming soil sickness in urban green areas through the integrated use of the natural silicon containing mineral analcite and a synthetic analog of allelochemical (salicylic acid). Materials and Methods. The experimental sites have been established in the most polluted and anthropogenically disturbed green areas of the Obolon District in Kyiv. The content of micro- and macro-elements, the main ecological-trophic groups of microorganisms have been evaluated, the directions of microbiological processes have been assessed with the use of mineralization and immobilization coefficients. Plant vitality has been determined by the degree of foliar injury, crown defoliation, photosynthetic pigment content, and activity of enzymatic antioxidants in leaves. Soil allelopathic activity has been determined by the bioassay technique. Results. Physical, chemical, and biological processes related to soil-sickness in urban areas have been studied and approaches to control these processes have been determined. The innovative technology to alleviate soil sickness in urban green areas has been tested. Conclusions. The advantage of the proposed technology is a complex synecological approach that which provides optimization of agrophysical, agrochemical, and biological characteristics of soil (optimal pH level, balanced content of mineral nutrients, elimination of toxicity), enhances the adaptive potential of cultivated plants to negative biotic and abiotic factors including phytopathogens.

No evidence for flooding stress memory in saplings of eight hardwood floodplain forest species

Alluvial floodplain forests became rare in many parts of Europe, due to anthropogenic changes. Therefore, restoration of floodplain forests is important, but a difficult task because of the complex environmental conditions. The zonation of woody species in floodplains is mainly determined by hydrological conditions, not only within one year but also during the previous years. Tolerance to flooding can be regarded as a key factor for the successful establishment. We examined whether a previous flooding showed an increased flooding tolerance of saplings from eight woody floodplain forest species after a recurrent flooding under controlled common garden conditions at the research station Gießen-Leihgestern (Germany). This would indicate a stress memory towards flooding stress. The individuals of the experiment already experienced a partial flooding of three different durations (three, six or nine weeks) or no flooding in the previous year. After nine months of recovery, these fourteen-month-old saplings were again either exposed to a partial flooding of nine weeks or no flooding. We assessed foliar injury and growth in terms of plant height, number of leaves and stem diameter three weeks (short-term recovery) and nine months (medium-term recovery) after flooding. The saplings showed no increased tolerance to a recurrent flooding irrespective of the previous experienced flooding duration. Therefore, no immediate stress memory towards flooding stress could be observed. To recover after flooding seems to be the better option compared to forming a stress memory, which explained that most species showed a decreased foliar injury after medium-term compared to short-term recovery period.

The impact of elevated ozone on growth, secondary metabolites, production of reactive oxygen species and antioxidant response in an anti-diabetic plant Costus pictus

Tropospheric ozone (O3) is a global air pollutant that causes deleterious effect to the plants. The present objective was to investigate the growth response, foliar injury, reactive oxygen species (ROS) accumulation and metabolites production in Costus pictus D. Don (insulin plant) at two developmental stages under ambient O3 (AO) and ambient + 20 ppb O3 (EO) using the open-top chambers (OTCs). A significant reduction in leaf area and total biomass was observed under EO as compared with AO. EO induced ROS (.O2- and H2O2) and lipid peroxidation led to more significant foliar injury and solute leakage. Image obtained from the fluorescence microscope and biochemical estimations reflected high levels of ROS under EO. A differential response in flavonoids and anthocyanin content, ascorbic acid, and antioxidative enzymes such as catalase (CAT), superoxide dismutase (SOD) and peroxidase (POX) has been observed with the growth stages of C. pictus plant. EO exposure negatively affected thiols and protein contents at all the growth stages. Secondary metabolites (tannins, lignin, saponins and alkaloids) were increased in both leaves and rhizomes due to EO, whereas phytosterols were induced only in rhizomes. Apart from other metabolites, the key bioactive compound (corosolic acid) showed its synthesis to be stimulated under EO at later growth stage. The study concludes that O3 is a potent stimulating factor for changing the levels of secondary metabolites and antioxidants in an antidiabetic C. pictus plants as it can alter its medicinal properties.

Visible symptoms and changes in physiological parameters of &lt;i&gt;Cinnamomum camphora&lt;/i&gt; and &lt;i&gt;Michelia chapensis&lt;/i&gt; under ozone stress

The responses of Cinnamomum camphora and Michelia chapensis to ozone (O3) exposure in terms of the O3 injury and changes in the physiological parameters of their leaves were examined in charcoal-filtered (CF) air and O3 at 1×, 2×, and 4×O3 ambient concentrations in open-top chambers in an eight-month experimental period. High levels of O3 exposure led to visible injuries in both species. The increased chlorophyll content in the second month and increased carotenoid content of the 1×O3 treatment group at the end of experiment were identified as hormetic-compensatory strategies that enhance tolerance and acclimation to O3 stress. Significant interaction effect between O3and tree species with respect to the superoxide dismutase (SOD) activity and proline content suggests that the effects induced by O3 were highly dependent on the tree species. C. camphora showed more foliar injury symptoms and greater O3-induced decreases in the chlorophyll, carotenoid, and protein contents than M. chapensis, which suggests that C. camphora is more sensitive to O3 than M. chapensis.

Assessing the effects of elevated ozone on physiology, growth, yield and quality of soybean in the past 40 years: A meta-analysis

Soybean (Glycine max) production is seriously threatened by ground-level ozone (O3) pollution. The goal of our study is to summarize the impacts of O3 on physiology, growth, yield, and quality of soybean, as well as root parameters. We performed meta-analysis on the collated 48 peer-reviewed papers published between 1980 and 2019 to quantitatively summarize the response of soybean to elevated O3 concentrations ([O3]). Relative to charcoal-filtered air (CF), elevated [O3] significantly accelerated chlorophyll degradation, enhanced foliar injury, and inhibited growth of soybean, evidenced by great reductions in leaf area (−20.8%), biomass of leaves (−13.8%), shoot (−22.8%), and root (−16.9%). Shoot of soybean was more sensitive to O3 than root in case of biomass. Chronic ozone exposure of about 75.5 ppb posed pronounced decrease in seed yield of soybean (−28.3%). In addition, root environment in pot contributes to higher reduction in shoot biomass and yield of soybean. Negative linear relationships were observed between yield loss and intensity of O3 treatment, AOT40. The larger loss in seed yield was significantly associated with higher reduction in shoot biomass and other yield component. This meta-analysis demonstrates the effects of elevated O3 on soybean were pronounced, suggesting that O3 pollution is still a soaring threat to the productivity of soybean in regions with high ozone levels.

Response of Sensitive and Resistant Snap Bean Genotypes to Nighttime Ozone Concentration

Effects of nighttime (2000 to 0700 hr) O3 on the pod mass of sensitive (S156) and resistant (R123) snap bean (Phaseolus vulgaris) genotypes were assessed using continuous stirred tank reactors located within a greenhouse. Two concentration-response relationship trials were designed to evaluate yield response to nighttime O3 exposure (10 to 265 ppb) in combination with daytime exposure at background levels (44 and 62 ppb). Three replicated trials tested the impact of nighttime O3 treatment at means of 145, 144, and 145 ppb on yields. In addition, stomatal conductance (gS) measurements documented diurnal variations and assessed the effects of genotype and leaf age. During the concentration-response experiments, pod mass had a significant linear relationship with the nighttime O3 concentration across genotypes. Yield losses of 15% and 50% occurred at nighttime exposure levels of ≈45 and 145 ppb, respectively, for S156, whereas R123 yields decreased by 15% at ≈150 ppb. At low nighttime O3 levels of ≈100 ppb, R123 yields initially increased up to 116% of the treatment that received no added nighttime O3, suggesting a potential hormesis effect for R123, but not for S156. Results from replicated trials revealed significant yield losses in both genotypes following combined day and night exposure, whereas night-only exposure caused significant decreases only for S156. The gS rates ranged from less than 100 mmol·m−2·s−1 in the evening to midday levels more than 1000 mmol·m−2·s−1. At sunrise and sunset, S156 had significantly higher gS rates than R123, suggesting a greater potential O3 flux into leaves. Across genotypes, younger rapidly growing leaves had higher gS rates than mature fully expanded leaves when evaluated at four different times during the day. Although these were long-term trials, gS measurements and observations of foliar injury development suggest that acute injury, occurring at approximately the time of sunrise, also may have contributed to yield losses. To our knowledge, these are the first results to confirm that the relative O3 sensitivity of the S156/R123 genotypes is valid for nighttime exposure.

Hyperspectral Reflectance of Light-Adapted Leaves Can Predict Both Dark- and Light-Adapted Chl Fluorescence Parameters, and the Effects of Chronic Ozone Exposure on Date Palm (Phoenix dactylifera).

High-throughput and large-scale measurements of chlorophyll a fluorescence (ChlF) are of great interest to investigate the photosynthetic performance of plants in the field. Here, we tested the capability to rapidly, precisely, and simultaneously estimate the number of pulse-amplitude-modulation ChlF parameters commonly calculated from both dark- and light-adapted leaves (an operation which usually takes tens of minutes) from the reflectance of hyperspectral data collected on light-adapted leaves of date palm seedlings chronically exposed in a FACE facility to three ozone (O3) concentrations (ambient air, AA; target 1.5 × AA O3, named as moderate O3, MO; target 2 × AA O3, named as elevated O3, EO) for 75 consecutive days. Leaf spectral measurements were paired with reference measurements of ChlF, and predictive spectral models were constructed using partial least squares regression. Most of the ChlF parameters were well predicted by spectroscopic models (average model goodness-of-fit for validation, R2: 0.53–0.82). Furthermore, comparing the full-range spectral profiles (i.e., 400–2400 nm), it was possible to distinguish with high accuracy (81% of success) plants exposed to the different O3 concentrations, especially those exposed to EO from those exposed to MO and AA. This was possible even in the absence of visible foliar injury and using a moderately O3-susceptible species like the date palm. The latter view is confirmed by the few variations of the ChlF parameters, that occurred only under EO. The results of the current study could be applied in several scientific fields, such as precision agriculture and plant phenotyping.

Screening of forty Indian Amaranthus hypochondriacus cultivars for tolerance and susceptibility to tropospheric ozone stress

Tropospheric ozone stress adversely affects crop cultivars growth and productivity variably. The variable response of crop cultivars raised the need for identification of ozone (O3) stress-tolerant cultivars as an adaptive option. In the present study, forty cultivars of Amaranthus hypochondriacus were screened for susceptibility and tolerance to ozone stress. The cultivars were exposed to ambient (AO3) and elevated (EO3) ozone levels in free air ozone enrichment (FAOE) facility and monitored for foliar ozone injury symptoms appearance and yield attributes response. Foliar ozone injury symptoms on Amaranthus cultivars were interveinal yellow or black spots. Foliar ozone injury was observed in almost half of the cultivars and the maximum foliar injury (> 75%) was observed in cultivar IC-5527. The maximum yield reduction (> 90%) was observed in cultivars IC-4200 (94.9%) and IC-5569 (91.4%) compared to other cultivars. The results showed that Amaranthus cultivars exhibited variable response towards ozone stress where foliar ozone injury does not always correspond with grain yield reductions. Among the indices, Relative Yield Index (RYI), Stress tolerance (TOL), Abiotic Tolerance Index (ATI), Susceptibility Index (S) and Stress Susceptibility Index (SSSI) were positively correlated with relative yield loss in all the cultivars under ozone stress. With the help of cluster analysis and principal component analysis (PCA), the cultivars were categorized into ozone tolerant, moderately ozone tolerant and ozone susceptible category. The most tolerant cultivars were IC-5527 and IC-1733 which exhibited lower yield losses whereas the most susceptible cultivars were IC-3599 and IC-7924 having high foliar injury and maximum yield losses as compared to other cultivars. The most ozone tolerant cultivars of Amaranthus identified in this study may be recommended for cultivation to farmers in the areas experiencing EO3 during the Amaranthus crop growth period.

An assessment of growth, floral morphology, and metabolites of a medicinal plant Sida cordifolia L. under the influence of elevated ozone.

Tropospheric ozone (O3) is a major secondary air pollutant and greenhouse gas, and its impact on growth, yield, and its quality is well established in the case of crop plants. However, the effects of tropospheric O3 have not been comprehensively studied on medicinal plants. Therefore, a field study was planned on a medicinally important Sida cordifolia L. plant (commonly known as country mallow or Bala) to assess the expected changes on the morphology, growth, and leaf injury under elevated O3 (ambient + 20ppb) by using open-top chambers (OTCs) at 30, 60, and 90days after treatment (DAT), while leaf and root metabolites were observed at 60 DAT. At all the growth stages, significant leaf damage was recorded as foliar injury symptoms. Most of the growth parameters also showed significant reductions at all the growth stages. Plants under elevated O3 showed a significant negative impact on most of the reproductive parts of the plant. Leaf weight ratio (LWR) showed significant increment at early stages while reduced at 90 DAT; however, root shoot ratio (RSR) showed a significant reduction at 60 DAT. The majority of the steroid metabolites showed an increase in root and leaves under elevated O3, while terpenes showed variable response. Due to O3 stress, most of the major metabolites showed an increase possibly due to their role in defense and other metabolic activities. Based on the outcomes, it is concluded that the future increase in the levels of tropospheric O3 will impact a significant effect on important metabolites of medicinal plants growing in tropical countries like India.

Influence of flooding duration and aeration on saplings of ten hardwood floodplain forest species.

Alluvial floodplain forests have been reduced drastically in many parts of Europe, due to deforestation, the transformation to settlement and expansion of agricultural areas. Although they have been heavily modified for centuries, generalized frameworks for their management are scarce and the complex interactions between the physical environment and biological processes are often not fully understood. As the zonation of woody species in floodplains is mainly determined by hydrological conditions, flooding tolerance can be regarded as a key factor for the successful establishment of woody species. Furthermore, the oxygen level of the flooding water might affect the responses to flooding. We examined the influence of flooding duration in combination with oxygen supply by aeration on the foliar injury and growth of six-week-old saplings of ten woody species, under controlled common garden conditions. Six of them are considered to be flooding tolerant whereas four are intolerant. In addition, seven are native whereas three are non-native species. During the experiment, the saplings were exposed to partial flooding of different durations (k = 3; three, six and nine weeks) and oxygen levels (k = 2; aerated and not aerated). For comparison, we included an unflooded control. We recorded foliar injury, plant height, number of leaves and stem diameter. We also included a long-term recovery period. Whereas foliar injury decreased for most species with increasing flooding duration, the typical floodplain forest species, classified as flooding tolerant developed better. The differences in species response to flooding could be most likely explained by their ability to react to the resulting stress in morphological, physiological and metabolic terms irrespective whether they are native or not. In addition, the inclusion of a recovery period seems to be important for the assessment of flooding tolerance.