O3-sensitive Cultivar Research Articles

Investigating the potency of ethylenediurea (EDU) in alleviating the affliction of ambient ozone in heat labile tomato cultivars (Solanum lycopersicum L.).

Tomato is the second most valuable vegetable crop, and its susceptibility to tropospheric ozone (O3) varies on the cultivar. Eight tomato cultivars with documented O3 sensitivity were reevaluated using ethylenediurea (400ppm EDU) to determine the effectiveness of EDU in assessing O3 sensitivity under heavily O3-polluted tropical conditions. EDU helped in amending the growth, photosynthetic pigments, photosynthetic rate, stomatal conductance, and yield characteristics in the tomato cultivars. EDU reduced the lipid peroxidation and reactive oxygen species content, while enzymatic and non-enzymatic antioxidant responses differed across cultivars. The cultivar Superbug and Sel-7 (O3 susceptible) performed better by employing more biomass and yield and exhibiting more potent antioxidative defense machinery mainly non-enzymatic antioxidants after EDU treatment. The higher value of total antioxidative potential (TAP) in O3 susceptible cultivars suggested the adaptive resilience through EDU application against O3 stress. EDU application greatly enhanced the photosynthetic rate in O3 susceptible cultivars by increasing the stomatal conductance. Hence, both biophysical and biochemical responses were involved in protection against O3 provided by EDU. Kashi chayan and VRT02 (O3 tolerant) cultivars showed least response to EDU, due to their efficient inherent mechanisms in alleviating O3 stress. Thus, EDU may be used as an efficient biomonitoring tool against O3-sensitive cultivars.

Divergent responses of ascorbate and glutathione pools in ozone-sensitive and ozone-tolerant wheat cultivars under elevated ozone and carbon dioxide interaction

Crop plants face complex tropospheric ozone (O3) stress, emphasizing the need for a food security-focused management strategy. While research extensively explores O3's harmful effects, this study delves into the combined impacts of O3 and CO2. This study investigates the contrasting responses of O3-sensitive (PBW-550) and O3-resistant (HUW-55) wheat cultivars, towards elevated ozone (eO3) and elevated carbon dioxide (eCO2), both individually and in combination. The output of the present study confirms the positive effect of eCO2 on wheat cultivars exposed to eO3 stress, with more prominent effects on O3-sensitive cultivar PBW-550, as compared to the O3-resistant HUW-55. The differential response of the two wheat cultivars can be attributed to the mechanistic variations in the enzyme activities of the Halliwell-Asada pathway (AsA-GSH cycle) and the ascorbate and glutathione pool. The results indicate that eCO2 was unable to uplift the regeneration of the glutathione pool in HUW-55, however, PBW-550 responded well, under similar eO3 conditions. The study's findings, highlighting mechanistic variations in antioxidants, show a more positive yield response in PBW-550 compared to HUW-55 under ECO treatment. This insight can inform agricultural strategies, emphasizing the use of O3-sensitive cultivars for sustained productivity in future conditions with high O3 and CO2 concentrations.

Efficiency of protectants in alleviating ozone stress on rice cultivars (Oryza sativa L.)

Tropical countries like India, as a result of increased greenhouse gases like tropospheric ozone (O3), are concerned about a loss of agricultural output and food security. As a result, adopting a new method to protect crops against ozone is a must. The most efficient protectant is ethylene diurea (EDU), which is often used by researchers, however, the effectiveness of other protectants remains still unexplored. Hence, this study aims in screening the potential protectants in alleviating the ozone stress (100 ppb) in O3 sensitive rice cultivar in open top chambers. The protectants used includes neem coated urea (NCU), ascorbic acid (AsA), calcium acetate (CaAc), panchagavya, neem oil, pink pigmented facultative methylotrophs (PPFM) and ethylene diurea (EDU). Results indicate that besides EDU, NCU and AsA were highly effective in mitigating O3 stress and were on par with each other. The application of protectants significantly improved the physiological, growth, and yield attributes; while, the malondialdehyde and proline content declined. The effect of protectants was relatively higher in O3 – sensitive cultivar. . The growth and yield traits were observed to be higher in EDU > NCU, AsA > CaAc > Panchagavya > Neem oil > PPFM. In O3 – sensitive cultivar, application of 300 ppm EDU, 1% NCU, and 1% AsA decreased the malondialdehyde content by 26.82, 26.92 and 27.47%, and proline by 18.64, 17.88 and 14.33%, respectively. Similarly, the application of 300 ppm EDU, 1% NCU and 1% AsA improved the number of spikelets per panicle by 69.09, 63.64 and 58.15% and the number of filled spikelets per panicle by 95.97, 95.35 and 93.02%, respectively. The present study concludes that NCU and AsA are the best alternatives to EDU for protecting plants against ozone stress.

Cascading effects of elevated ozone on wheat rhizosphere microbial communities depend on temperature and cultivar sensitivity

Tropospheric ozone (O3) concentrations have now reached levels that can potentially affect crop production in several regions of the world. The interacting effects of the elevated O3 and temperature on plants are still unclear and their consequences on the rhizosphere microbial communities never studied yet. Here, we conducted a 3-week fumigation experiment on two cultivars of wheat with different tolerance to O3 (Premio and Soissons) at two temperatures (20 °C and 30 °C). The impacts of O3 were measured on plants physiology, rhizosphere chemical environment and microbial communities. Globally, most of the results showed that elevated O3 effects were more pronounced at 20 °C than 30 °C, especially on the most O3-sensitive cultivar (Soissons). Elevated O3 reduced significantly plant root biomass (up to −37% for Soissons) compared to non-fumigated plants. A decrease in the dissolved organic matter with a relative increase of aromatic compounds concentration was also observed under elevated O3, suggesting quantitative and qualitative impacts on roots exudation. While bacterial abundance was negatively affected by O3 plant stress, fungal abundance was found to be stimulated (up to 12 fold compared to non-fumigated plants for Soissons at 20 °C). These changes were accompanied by modifications of the genetic structures and metabolic profiles, with a relative increase of amino acids catabolism. This fully controlled laboratory experiment showed that the effects of elevated O3 on soil microbial communities i) are plant-mediated and depend on the cultivar sensitivity, ii) decrease in warming condition, iii) increase the fungi to bacteria ratio and iv) alter both the genetic structure and the metabolic activities. This study highlights the importance of considering interactive effects between pollutants and climate changes on plant-microbe relationship to better inform models and improve predictions of future states of agroecosystems.

Elevated ozone effects on soil nitrogen cycling differ among wheat cultivars

Elevated O3 (eO3) has strong effects on natural and managed ecosystems, including decreased plant growth, plant tissue quality, species richness, plant litter inputs, decomposition, and root turnover. However, the effects of eO3 on soil nitrogen (N) cycling are poorly understood. Here, a free -air O3 enrichment experiment was conducted from 2007 to 2012, in which two O3-tolerant wheat cultivars and two O3-sensitive cultivars were grown under ambient O3 (aO3, 40 ppb) and eO3 (60 ppb). We used a 15N pool dilution technique to investigate N transformation rates and N availability in the soils in 2012. Both gross and net N transformation rates were significantly decreased (P<0.05) by eO3 in soils growing sensitive wheat cultivars, but were unchanged in soils growing tolerant cultivars. Compared with aO3, NH4+ and NO3− concentrations were significantly increased (P<0.05) by eO3 in soils growing sensitive cultivars but not in soils growing tolerant cultivars. Ammonia monooxygenase activity was significantly increased by eO3 while nitrate reductase activity was significantly decreased. Additionally, redundancy analysis (RDA) suggested that microbial community structure was largely shaped by soil and plant characteristics such as DOC, root C/N ratio, MBC/MBN, shoot/root ratio, root N, soil N and pH. In conclusion, wheat cultivars play an important role in determining the effects of elevated O3 on N transformations. This study provides new insights into our understanding of how changes in microbial diversity and metabolism as mediated by plants will alter N cycling and ecosystem N availability in response to eO3 and suggests that these effects will differ among different plants.

Elevated ozone increases nitrifying and denitrifying enzyme activities in the rhizosphere of wheat after 5 years of fumigation

Backgrounds and aims Nitrogen (N) cycling in agroecosystems is likely to change under elevated O3 (eO3) as a result of changes in plant material inputs to soils. The objective of this study was to understand how eO3 could change key N cycling processes in soils. Methods Rhizosphere soils were collected from sensitive and tolerant wheat cultivars following a 5-year fumigation of O3at 60 ppb (eO3) and at ambient 40 ppb (aO3 )i n a free-air ozone enrichment platform. Soil nitrifying and denitrifying enzymeactivity(NEA andDEA), abundance of ammonia monooxygenase(amoA) and denitrifying bacteriagenes(nirSandnirK), and other related properties were quantified. Results Soil NEA, DEA, NH4 + and NO3 � were higher under eO3 than under aO3, whereas microbial biomass N (MBN) decreased under eO3 ,e specially with the O3sensitive cultivar. No clear eO3 effect was observed on the abundance of amoA and nirS and nirK. Grain yield and shoot to root ratios decreased as a result of eO3 in the O3-sensitive cultivar. Conclusions eO3 stimulates soil N availability, but suppresses grain yields after 5 years, especially for the O3sensitive cultivar. Adaptivestrategiesshould focus more on cultivar selection to retain N in soil and to assure the resilience of crop production in the future.

Growth and yield responses of potato to mixtures of carbon dioxide and ozone.

Elevated carbon dioxide (CO2) concentrations in the atmosphere can stimulate plant growth and yield, whereas ground-level ozone (O3) concentrations cause the opposite effect in many areas of the world. Recent experiments show that elevated CO2 can protect some plants from O3 stress, but this has not been tested for most crop species. Our objective was to determine if elevated CO2 protects Irish potato (Solanum tuberosum L.) from foliar injury and suppression of growth and yield caused by O3. An O3-resistant cultivar (Superior) and an O3-sensitive cultivar (Dark Red Norland) were exposed from within 10 d after emergence to maturity to mixtures of three CO2 and three O3 treatments in open-top field chambers. The three CO2 treatments were ambient (370 microL L(-1)) and two treatments with CO2 added to ambient CO2 for 24 h d(-1) (540 and 715 microL L(-1)). The O3 treatments were charcoal-filtered air (15 nL L(-1)), nonfiltered air (45 nL L(-1)), and nonfiltered air with O3 added for 12 h d(-1) (80 nL L(-1)). Elevated O3 and CO2 caused extensive foliar injury of Dark Red Norland, but caused only slight injury of Superior. Elevated CO2 increased growth and tuber yield of both cultivars, whereas elevated O3 generally suppressed growth and yield, mainly of Dark Red Norland. Elevated CO2 appeared to protect Dark Red Norland from O3-induced suppression of shoot, root, and tuber weight as measured at midseason but did not protect either cultivar from O3 stress at the final harvest. The results further illustrate the difficulty in predicting effects of O3 + CO2 mixtures based on the effects of the individual gases.

Effect of Host Plant Ozone Stress on Colorado Potato Beetles

Effects of ozone (O3) stress of potato, Solanum tuberosum L., on fecundity, larval growth and survival of Colorado potato beetles, Leptinotarsa decemlineata (Say), were measured in greenhouse and field experiments. Chronic O3 exposure caused moderate to severe foliar injury on an O3-sensitive cultivar (‘Red Norland’) but caused only minor injury an O3-resistant cultivar (‘Superior’). Foliar injury caused by O3 was greater on old than on young leaves but feeding by adult beetles was greater on young leaves in all experiments. Foliar analyses of the five uppermost leaves (nodes 1–5) showed higher carbon (C) and higher nitrogen (N) concentration in Superior than in Norland. There were no significant O3 effects on C or N and no cultivar × O3 interactions. Egg production by newly emerged adult beetles feeding on plants exposed to high O3 levels was not significantly different from egg production on plants exposed to low O3 levels, regardless of cultivar O3 sensitivity. Feeding and energy conversion efficiency of neonates and survival of larvae to the adult stage were not significantly affected by the O3 treatment. Although present levels of tropospheric O3 are high enough to significantly affect yield of sensitive potato cultivars, our results indicate no significant effect of ambient O3 concentrations on Colorado potato beetle populations.

Photoassimilate allocation and photosynthetic and biochemical characteristics of two alfalfa (Medicago sativa) cultivars of different ozone sensitivities

Ozone (O3) is a major air pollutant that has been reported to affect growth of alfalfa (Medicago sativa L.). In the present study, an O3-sensitive cultivar, 'Apica', and an O3-tolerant cultivar, 'Team', of alfalfa were exposed to multiple levels of ambient O3 concentrations (i.e., 0x, 1x, 1.5x, and 3x) using open-top chambers. The objectives were to characterize O3 sensitivities at the leaf level and to determine whether stomatal or mesophyll conductance could account for the differences in O3 sensitivity. Differences in photoassimilate allocation were also determined using 14CO2. Effects of O3 exposures on leaf characteristics such as leaf area and dry matter; leaf concentrations of chlorophyll, starch, proteins, amino acids, and nutrients; and stomatal density were evaluated. Gas exchange measurements were also performed. Results showed that O3 exposures produced a greater decline in leaf biomass, chlorophyll concentration, and net assimilation rate for 'Apica' compared with 'Team'. For O3 concentrations of 20-40 nL ·L-1, a 7-15% reduction in net assimilation rate was observed for 'Apica' only. With an increase in O3 concentrations, stomatal limitation did not increase correspondingly, and a strong correlation between net assimilation rate, stomatal conductance, and carboxylation efficiency was observed, suggesting a physiological coordination of the O3 stress response at the leaf level. Possibly the decrease in assimilation rate induced by O3 could be associated with the O3 effects at the mesophyll level. For both cultivars, O3 increased the CO2 compensation point of the leaves, and some effects were also noted in terms of leaf mineral concentrations. O3 did not alter photoassimilate allocation between shoots and roots but stimulated their retention in leaves compared with stems. These results suggest that O3 has a major impact on the carbon metabolism of leaves, which could explain differences in O3 sensitivities.Key words: gas exchange, ozone tolerance, alfalfa cultivars, stomata, photoassimilate allocation.

Sulfur dioxide-enhanced Phytotoxicity of Ozone to Watermelon

Three watermelon [Citrullus lanatus (Thunb.) Matsum &amp; Nakai] cultivars with different ozone (O3) sensitivities were grown in a charcoal-filtered greenhouse and exposed in continuous-stirred tank reactor chambers to five levels (0, 100, 200, 300, or 400 nL·L-1) of sulfur dioxide (SO2) in the presence (80 nL·L-1) or absence (0 nL·L-1) of ozone (O3) for 4 hours/day, 5 days/week for 22 days. In the presence of O3, SO2 increased foliar injury in all three cultivars, but the impact was greatest for the most O3-sensitive cultivar, `Sugar Baby,' moderate for `Crimson Sweet,' and least for the least O3-sensitive cultivar, `Charleston Gray.' For all cultivars, SO2 intensified O3 suppression of leaf area for the first seven mainstem leaves and of dry weights for aboveground and total plant tissues. Root dry weight was independently suppressed by both pollutants, and the root: top ratio was linearly suppressed by SO2 alone. Sulfur dioxide combined with O3 can be detrimental to crop species such as watermelon. Thus, the potential for SO2 phytotoxicity should not be summarily dismissed, especially in the vicinity of SO2 point sources where O3 co-occurs.

Activity of ribulose bisphosphate carboxylase/oxygenase from potato cultivars with differential response to ozone stress.

The effect of ozone (O3 ) on the carboxylation activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) from the fifth youngest leaf of four cultivars of Solarium tuberosum L. (potato) was investigated. Ozone-tolerant cultivars 'Superior' (SP) and 'Norgold Russet' (NR), and O3 -sensitive cultivars 'Cherokee' (CK) and 'Norland' (NL) were exposed to O3 for five consecutive days in controlled-environment chambers. Leaf samples were obtained during the O3 -exposure period and at 1, 5, and 10 d post-exposure. For both charcoal-filtered air (control) and O3 -treated foliage, total activity of Rubisco declined with increasing leaf age. Ozone induced an accelerated decline in the carboxylation activity of Rubisco in leaves obtained from CK and NL by the third day of O3 exposure. In contrast, O3 had no impact on the Rubisco activity from leaves of SP and NR as compared to non-treated foliage. Differential foliar conductance could not account for the response of the sensitive and tolerant cultivars. Rubisco was purified from cultivars SP and CK to determine whether protein sulphydryl content correlated with foliar O3 sensitivity. The number of SH groups did not differ between the two cultivars, either in chemically denatured or non-denatured Rubisco. Consequently, neither number nor availability of SH groups appear to be factors controlling sensitivity of Rubisco to oxidative damage by O3 .