scholarly journals Dynamics of Foliar Responses to O3 Stress as a Function of Phytotoxic O3 Dose in Hybrid Poplar

2021 ◽  
Vol 12 ◽  
Author(s):  
Benjamin Turc ◽  
Pierre Vollenweider ◽  
Didier Le Thiec ◽  
Anthony Gandin ◽  
Marcus Schaub ◽  
...  
Keyword(s):  
Leaf Age ◽  
Hybrid Poplar ◽  
Latency Period ◽  
Background Concentrations ◽  
Wood Production ◽  
Response Dynamics ◽  
Visible Injury ◽  
Gas Exchanges ◽  
Economic Significance ◽  
Biomass Reduction

With background concentrations having reached phytotoxic levels during the last century, tropospheric ozone (O3) has become a key climate change agent, counteracting carbon sequestration by forest ecosystems. One of the main knowledge gaps for implementing the recent O3 flux-based critical levels (CLs) concerns the assessment of effective O3 dose leading to adverse effects in plants. In this study, we investigate the dynamics of physiological, structural, and morphological responses induced by two levels of O3 exposure (80 and 100 ppb) in the foliage of hybrid poplar, as a function of phytotoxic O3 dose (POD0) and foliar developmental stage. After a latency period driven by foliar ontological development, the gas exchanges and chlorophyll content decreased with higher POD0 monotonically. Hypersensitive response-like lesions appeared early during exposure and showed sigmoidal-like dynamics, varying according to leaf age. At current POD1_SPEC CL, notwithstanding the aforementioned reactions and initial visible injury to foliage, the treated poplars had still not shown any growth or biomass reduction. Hence, this study demonstrates the development of a complex syndrome of early reactions below the flux-based CL, with response dynamics closely determined by the foliar ontological stage and environmental conditions. General agreement with patterns observed in the field appears indicative of early O3 impacts on processes relevant, e.g., biodiversity ecosystem services before those of economic significance – i.e., wood production, as targeted by flux-based CL.

scholarly journals Meteorological conditions, ozone concentration and leaf age affect gas exchange in Psidium guajava ‛Palumaʼ

Hoehnea ◽  
2017 ◽  
Vol 44 (2) ◽  
pp. 236-245 ◽  
Author(s):  
Juliana Moreno Pina ◽  
Sérgio Tadeu Meirelles ◽  
Regina Maria de Moraes
Keyword(s):  
Gas Exchange ◽  
Ozone Concentration ◽  
Leaf Age ◽  
Psidium Guajava ◽  
Meteorological Conditions ◽  
Gas Exchanges ◽  
Mature Leaves ◽  
Young Leaves ◽  
Entire Experiment ◽  
The City

ABSTRACT This study aimed to investigate the importance of leaf age, meteorological conditions and ozone concentration (O3) on gas exchange of Psidium guajava ‛Paluma'. Saplings were grown and exposed in standard conditions in the city of São Paulo, in six periods of three months with weekly measurements in young and mature leaves. Gas exchanges were higher in young leaves for almost the entire experiment. Mature leaves showed greater reduction in gas exchange. The multivariate analysis of biotic and abiotic variables indicated that vapor pressure deficit (VPD), O3 concentration and radiation were the main variables associated with gas exchange decrease in young leaves. In mature leaves the influence of VPD is lower, but the temperature importance is higher. Moreover, the opposition between assimilation and O3 is more evident in mature leaves, indicating their greater sensitivity to O3.

Improved herbicide selectivity in tomato by safening action of benoxacor and fenclorim

2020 ◽  
Vol 34 (5) ◽  
pp. 647-651
Author(s):  
Edicarlos Castro ◽  
Carolina Pucci ◽  
Stefano Duarte ◽  
Nilda Roma Burgos ◽  
Te Ming Tseng
Keyword(s):  
Seed Treatment ◽  
Mechanisms Of Action ◽  
Shoot Biomass ◽  
Glutathione S Transferase ◽  
Visible Injury ◽  
Factor B ◽  
Tomato Plants ◽  
Alternative Weed Control ◽  
Biomass Reduction ◽  
Gst Activity

AbstractSafeners have been widely used to reduce phytotoxicity to crops, thus serving as an alternative weed control strategy. Benoxacor and fenclorim safeners have the potential to protect plants from herbicide phytotoxicity by increasing glutathione S-transferase (GST) activity within the plant. The study aimed to evaluate the safening effect of benoxacor and fenclorim on tomato against selected herbicides applied POST. The experiment was conducted in a greenhouse in a completely randomized designed with four replications in a 9 × 3 factorial scheme, where Factor A consisted of eight herbicides including a nontreated control, and Factor B consisted of two safeners including a nontreated control. The herbicide treatments were sulfentrazone (0.220 kg ai ha−1), fomesafen (0.280 kg ai ha−1), flumioxazin (0.070 kg ai ha−1), linuron (1.200 kg ai ha−1), metribuzin (0.840 kg ai ha−1), pyroxasulfone (0.220 kg ai ha−1), and bicyclopyrone (0.040 kg ai ha−1). Safener treatments consisted of benoxacor (0.67 g L−1) and fenclorim (10 µM). Tomato seeds were immersed in safener solution before sowing and herbicides were applied when tomato plants were at the 3-leaf stage, or 25 days after sowing. Visible injury was scored at 3, 7, 14, and 21 d after application (DAA), and shoot biomass was recorded 21 DAA. Seed treatment with fenclorim reduced injury caused by imazamox and bicyclopyrone by 5.5 and 1.3 times, respectively, whereas benoxacor reduced the injury from bicyclopyrone 1.3 times. In addition, tomato plants pretreated with fenclorim showed a lesser reduction in biomass after application of imazamox, fomesafen, and metribuzin, whereas plants pretreated with benoxacor showed lesser biomass reduction after metribuzin application. Thus, the use of safeners promotes greater crop selectivity, allowing the application of herbicides with different mechanisms of action on the crop.

scholarly journals The Impact of Phloem Feeding Insects on Leaf Ecophysiology Varies With Leaf Age

2021 ◽  
Vol 12 ◽  
Author(s):  
Sylvain Pincebourde ◽  
Jérôme Ngao
Keyword(s):  
Growth Rate ◽  
Stomatal Conductance ◽  
Gas Exchange ◽  
Carbon Content ◽  
Nitrogen Content ◽  
Leaf Gas Exchange ◽  
Leaf Age ◽  
Leaf Nitrogen Content ◽  
Gas Exchanges ◽  
Young Leaves

Herbivore insects have strong impacts on leaf gas exchange when feeding on the plant. Leaf age also drives leaf gas exchanges but the interaction of leaf age and phloem herbivory has been largely underexplored. We investigated the amplitude and direction of herbivore impact on leaf gas exchange across a wide range of leaf age in the apple tree–apple green aphid (Aphis pomi) system. We measured the gas exchange (assimilation and transpiration rates, stomatal conductance and internal CO2 concentration) of leaves infested versus non-infested by the aphid across leaf age. For very young leaves up to 15 days-old, the gas exchange rates of infested leaves were similar to those of non-infested leaves. After few days, photosynthesis, stomatal conductance and transpiration rate increased in infested leaves up to about the age of 30 days, and gradually decreased after that age. By contrast, gas exchanges in non-infested leaves gradually decreased across leaf age such that they were always lower than in infested leaves. Aphids were observed on relatively young leaves up to 25 days and despite the positive effect on leaf photosynthesis and leaf performance, their presence negatively affected the growth rate of apple seedlings. Indeed, aphids decreased leaf dry mass, leaf surface, and leaf carbon content except in old leaves. By contrast, aphids induced an increase in leaf nitrogen content and the deviation relative to non-infested leaves increased with leaf age. Overall, the impacts of aphids at multiple levels of plant performance depend on leaf age. While aphids cause an increase in some leaf traits (gas exchanges and nitrogen content), they also depress others (plant growth rate and carbon content). The balance between those effects, as modulated by leaf age, may be the key for herbivory mitigation in plants.

The effect of a continuous springtime fumigation with SO2 on CO2 uptake and structure of the annual ring in spruce

1980 ◽  
Vol 10 (1) ◽  
pp. 1-6 ◽  
Author(s):  
T. Keller
Keyword(s):  
Annual Ring ◽  
Ring Width ◽  
Co2 Uptake ◽  
Gas Analyzer ◽  
Wood Production ◽  
Visible Injury ◽  
X Ray ◽  
Late Wood ◽  
Infrared Gas Analyzer ◽  
Stem Slices

Potted grafts of old spruces (Piceaabies (L.) Karst.) were continuously fumigated with SO2 (contro1, 0.05, 0.1, and 0.2 ppm) in outdoor fumigation chambers. SO2 concentrations were maintained for 10 weeks from late in April till early in July 1976. CO2 uptake was measured periodically under standardized laboratory conditions with an infrared gas analyzer. After fumigation, the plants remained in the nursery till November 1977. Afterwards, stem slices were taken for X-ray measurements of both ring width and wood density. An arbitrary density of 0.5 g cm−3 was chosen to distinguish early wood from late wood. CO2 uptake was depressed significantly before visible symptoms of injury appeared. The relative CO2 uptake in the 7th to 10th week of fumigation and the number of cells in a radial file of the annual ring were well correlated. With increasing SO2 concentration, the width of the annual ring decreased. The amount and density of late wood was reduced by a springtime fumigation. A distinct decline of wood production with increasing SO2 concentration was also found in cases where no visible injury occurred.

Impact of ozone and sulfur dioxide on net photosynthesis of hybrid poplar cuttings

1984 ◽  
Vol 14 (3) ◽  
pp. 385-388 ◽  
Author(s):  
K. F. Jensen ◽  
R. D. Noble
Keyword(s):  
Respiration Rate ◽  
Hybrid Poplar ◽  
Net Photosynthesis ◽  
Compensation Point ◽  
Visible Injury ◽  
Photosynthetic Rates ◽  
Treatment Groups ◽  
Point Data ◽  
Poplar Cuttings ◽  
Air Control

Softwood cuttings of hybrid poplar clone No. 207 (Populusdeltoides Bartr. × Populustrichocarpa Torry and Gray) were fumigated with either charcoal-filtered air (control), 0.5 ppm SO2, or 0.5 ppm SO2 + 0.25 ppm O3 for 12 h each day for 3 weeks. The net photosynthetic rate and CO2 compensation point were then measured in a closed-loop gas assimilation system with an infrared gas analyzer. Net photosynthesis was measured at light intensities of 430 and 730 μE•m−2•s−1 (photosynthetically active radiation) and in CO2 concentrations of 300, 500, and 1000 ppm. Net photosynthesis increased with an increase in light intensity and CO2 concentration but was significantly reduced by the SO2 + O3 treatment. The leaves were classified into five groups on the basis of visible injury. There were no significant differences in the net photosynthetic rates among uninjured leaves in the three fumigation treatments. However, analysis of the data from the SO2 + O3 treatment, which separated the leaves into injury classes, showed that the CO2 – injury class interaction was significant. At 300 ppm CO2, there were no significant differences in the net photosynthetic rates among the five injury classes. At 500 and 1000 ppm CO2, there were significant differences in the photosynthetic rates between leaves without visible injury and those with injury. Photosynthesis in the injured leaves may have been suppressed by an increase in the respiration rate and a decrease in the photosynthetic area. The increased respiration rate is suggested by the CO2 compensation point data that was significantly higher in all of the fumigated leaves. There were no significant differences in the chlorophyll content of the leaves from the three treatment groups.

scholarly journals Herbicide strategies for managing glyphosate-resistant and susceptible kochia (Bassia scoparia) in spring wheat

2021 ◽  
Author(s):  
Alysha T Torbiak ◽  
Robert Blackshaw ◽  
Randall N Brandt ◽  
Bill Hamman ◽  
Charles M. Geddes
Keyword(s):  
Spring Wheat ◽  
Acetolactate Synthase ◽  
Management Program ◽  
Integrated Weed Management ◽  
Western Canada ◽  
Management Options ◽  
Visible Injury ◽  
Herbicide Resistant ◽  
Als Inhibitor ◽  
Biomass Reduction

Kochia [<i>Bassia scoparia</i> (L.) A.J. Scott] is a summer-annual tumbleweed that is tolerant of heat, drought and salinity, and capable of causing large yield losses in spring wheat (<i>Triticum aestivum</i> L). Increased incidence of glyphosate and acetolactate synthase (ALS) inhibitor-resistant kochia in Western Canada warrants investigation of alternative herbicides to manage these biotypes. Herbicides applied pre- or post-emergence in spring wheat were evaluated based on crop tolerance and control of ALS inhibitor-resistant kochia accessions with and without the glyphosate resistance trait in five environments near Lethbridge and Coalhurst, Alberta, from 2013-2015. The most effective and consistent treatments for kochia management included sulfentrazone applied pre-emergence, and fluroxypyr/bromoxynil/2,4-D or pyrasulfotole/bromoxynil applied post-emergence. All of these treatments resulted in ≥ 90% visible control in all environments and ≥ 90% kochia biomass reduction compared with the untreated control in Lethbridge 2014 and 2015. MCPA/dichlorprop-p/mecoprop-p, dicamba/2,4-D/mecoprop-p, and dicamba/fluroxypyr resulted in acceptable control among environments (≥ 80% visible control in all environments and ≥ 80% kochia biomass reduction in Lethbridge 2014 and 2015); however the latter two options caused unacceptable (> 10%) wheat visible injury in Coalhurst 2014. Recent confirmations of auxinic herbicide-resistant kochia in Western Canada – due, in part, to use of synthetic auxins to manage glyphosate-resistant kochia in small-grain cereals – will limit kochia management options. When implemented with non-chemical tools as part of an integrated weed management program, alternative herbicide modes of action like protoporphyrinogen oxidase inhibitors before and photosystem II or 4-hydroxyphenylpyruvate dioxygenase inhibitor(s) within spring wheat could mitigate selection for multiple herbicide-resistant kochia.

Volunteer Barley (Hordeum vulgare) Control in Winter Wheat (Triticum aestivum) with MON 37500

1999 ◽  
Vol 13 (1) ◽  
pp. 88-93 ◽  
Author(s):  
Sandra L. Shinn ◽  
Donald C. Thill ◽  
William J. Price
Keyword(s):  
Winter Wheat ◽  
Spring Barley ◽  
Wheat Crop ◽  
Growth Stages ◽  
Visible Injury ◽  
Yield And Quality ◽  
Control Volunteer ◽  
Winter Wheat Crop ◽  
Grain Yield And Quality ◽  
Biomass Reduction

Spring barley often is grown in rotation with winter wheat, and sometimes barley can overwinter in the subsequent winter wheat crop reducing grain yield and quality. Studies were established during 1996 and 1997 in winter wheat fields in southeastern Washington and near Moscow, ID, respectively, to evaluate control of ‘Steptoe’ volunteer barley with MON 37500, diclofop, and fenoxaprop/2,4-D/MCPA. Herbicides were applied to volunteer barley at two growth stages: two leaves to four tillers and more than four tillers with stems beginning to elongate. MON 37500 at 0.018, 0.026, and 0.035 kg ai/ha visibly controlled volunteer barley 83% or more at both application times. Diclofop at 1.12 kg ai/ha did not control volunteer barley, whereas fenoxaprop/2,4-D/MCPA at 0.66 kg ai/ha controlled volunteer barley 64 to 97% in 1996, but only 0 to 23% in 1997. In 1996 and 1997, volunteer barley density was reduced 80 to 99% in MON 37500-treated plots compared to the untreated control plots. Wheat grain grade was #1 for all MON 37500 treatments compared to grade #4 in 1996 and #3 in 1997 in the untreated plots. Grain price was reduced by dockage (barley kernels) for MON 37500-treated wheat $0 to $3.12/metric ton (MT), whereas price was reduced $23 to $26/MT for grain from untreated plots. In greenhouse studies, visible injury and height and biomass reduction varied among the 36 barley varieties treated with MON 37500.

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