Surface ozone risk to human health and vegetation in tropical region: The case of Thailand.

Tropospheric ozone (O3) is a threat to vegetation and human health over the world, in particular in Asia. Knowledge on O3 impacts on tropical ecosystems is still very limited. An O3 risk assessment to crops, forests, and people from 25 monitoring stations across the tropical and subtropical Thailand during 2005-2018 showed that 44% of sites exceeded the critical levels (CLs) of SOMO35 (i.e., the annual Sum Of daily maximum 8-h Means Over 35 ppb) for human health protection. The concentration-based AOT40 CL (i.e., sum of the hourly exceedances above 40 ppb for daylight hours during the assumed growing season) was exceeded at 52% and 48% of the sites where the main crops rice and maize are present, respectively, and at 88% and 12% of the sites where evergreen or deciduous forests are present, respectively. The flux-based metric PODY (i.e., Phytotoxic Ozone Dose above a threshold Y of uptake) was calculated and was found to exceed the CLs at 1.0%, 1.5%, 20.0%, 1.5%, 0% and 68.0% of the sites where early rice, late rice, early maize, late maize, evergreen forests, and deciduous forests can grow, respectively. Trend analysis indicated that AOT40 increased over the study period (+5.9% year-1), while POD1 decreased (- 5.3% year-1), suggesting that the role of climate change in affecting the environmental factors that control stomatal uptake cannot be neglected. These results contribute novel knowledge on O3 threat to human health, forest productivity, and food security in tropical and subtropical areas.

The potential of proline as a key metabolite to design real-time plant water deficit and low-light stress detector in ornamental plants.

Nowadays, people are interested to use plants, especially air-purifying plants, in residential and other indoor settings to purify indoor air and increase the green area in the building. In this study, we investigated the effect of water deficit and low light intensity on the physiology and biochemistry of popular ornamental plants, including Sansevieria trifasciata, Episcia cupreata and Epipremnum aureum. Plants were grown under low light intensity in the range of 10-15 µmol quantum m-2 s-1 and 3 days of water deficit. The results showed that these three ornamental plants responded to water deficit with different pathways. Metabolomic analysis indicated that water deficit affected Episcia cupreata and Epipremnum aureum by inducing a 1.5- to 3-fold increase of proline and a 1.1- to 1.6-fold increase in abscisic acid compared to well-watered conditions, which led to hydrogen peroxide accumulation. This resulted in a reduction of stomatal conductance, photosynthesis rate and transpiration. Sansevieria trifasciata responded to water deficit by significantly increasing gibberellin by around 2.8-fold compared to well-watered plants and proline contents by around 4-fold, while stomatal conductance, photosynthesis rate and transpiration were maintained. Notably, proline accumulation under water deficit stress could be attributed to both gibberellic acid and abscisic acid, depending on plant species. Therefore, the enhancement of proline accumulation in ornamental plants under water deficit could be detected early from day 3 after water deficit conditions, and this compound can be used as a key compound for real-time biosensor development in detecting plant stress under water deficit in a future study.

Possibility to Apply Strontium Aluminate to Produce Light-Emitting Plants: Efficiency and Safety.

Light-emitting plants (LEPs) provides light in areas without electricity. The phosphorescent compound was used as a lighting material for LEP development. However, using the phosphorescent compound for LEPs development required optimization and phytotoxicity evaluation. Strontium aluminate (SrAl2 O4 ) is a phosphorescent compound that can glow for a long time and is easily recharged by visible light. In this study, using SrAl2 O4 to develop LEPs was evaluated. Additionally, plant stress under SrAl2 O4 was investigated. Metabolomic analysis can explain the possible mechanism of plants' stress under SrAl2 O4 . After, injecting 3 mL of 5 % (w/v) SrAl2 O4 products 1, 2, and 3 into the stem of Ipomoea aquatica, the result showed that SrAl2 O4 products 2 and 3 caused oxidative stress. The metabolomic analysis also indicated that I. aquatica responded to SrAl2 O4 product 1 by increasing pipecolic acid and salicylic acid, while I. aquatica injected with SrAl2 O4 products 2 and 3 showed a decrease in salicylic acid around 0.005 and 0.061-fold, respectively, compared to control plants. and an excess accumulation of MDA around 10.00-12.00 µmol g-1 FW. A 15 % concentration of SrAl2 O4 can be used for LEPs development, enabling photoemission 18-fold for 50 min. SrAl2 O4 product 1 has the potential to be a material for LEPs.

Mechanisms of ozone responses in sensitive and tolerant mungbean cultivars.

Ozone (O 3) is one of the major air pollutants, with negative impacts on human health, vegetation and agricultural production. It affects plants by reducing green leaf area and leading to necrosis, lesions and chlorosis, resulting in yield loss. Four mungbean cultivars were used to study O 3 sensitivity under elevated O 3 concentrations in the range of 70-100 ppb in an O 3 open-top chamber during the growing season. Based on O 3 response mechanisms, we classified mungbean cultivars into two groups: (1) O 3 -sensitive cultivars (Chainat 3 and 4) and (2) O 3 -tolerant cultivars (Chainat 84-1-1 and Kampangsan 2). The most O 3 -sensitive cultivars (Chainat 4) had the highest visible injury symptoms and the lowest in plant biomass. This evidence was due to Chainat 4 had lower ascorbic acid, indole acetic biosynthesis protein, defence related protein related to antioxidant systems, attribute to higher H 2 O 2 accumulation and an increase in salicylic acid contents. In contrast to the most O 3 -tolerant cultivars (Chainat 84-1-1) which had higher ascorbic acid levels, an upregulation of defence related protein, especially ascorbic acid biosynthesis and regenerate, indole acetic acid and jasmonic acid biosynthesis protein resulting in balanced H 2 O 2 levels, lower salicylic acid accumulation and little visible injury under elevated O 3 concentrations. Therefore, we conclude that the increased abundance of indole acetic acid, antioxidant related proteins facilitating stomata physiology in O 3 -tolerant under O 3 stress. This is the first report of the responses of mungbean cultivars in Thailand to elevated O 3 concentrations, facilitating the selection of suitable cultivars and the biomonitoring of O 3 levels.

Effect of exogenous catechin and salicylic acid on rice productivity under ozone stress: the role of chlorophyll contents, lipid peroxidation, and antioxidant enzymes.

Increasing ozone concentration is one of the oxidative stresses that affects rice yield loss in many countries. Catechin and salicylic acid were proposed as tools for alleviating oxidative stress in plants, but their roles in protecting rice productivity under ozone stress still remained unknown. We investigated the mechanism of catechin and salicylic acid on rice under ozone stress at the vegetative stage and at the reproductive stage. Rice was sprayed with catechin and salicylic acid before exposure to ozone in the range of 100-150 ppb (8 h day-1). Ozone and salicylic acid led to a decrease in chlorophyll contents, magnesium contents, and stomatal conductance. This evidence led to a decrease in rice productivity and quality. In contrast, under rice + catechin, both ambient air and elevated ozone conditions had to higher rice productivity and quality than under rice alone and rice + salicylic acid conditions. Catechin could mitigate ozone stress in rice plants through maintaining chlorophyll contents, magnesium contents, and stomatal conductance. Moreover, catechin could induce an unregulation of ascorbate peroxidase, and catalase genes led to increasing their antioxidant enzyme activity. Increasing of antioxidant enzyme activity under rice + ozone + catechin conditions attributed to lower lipid peroxidation than under rice + ozone especially at vegetative stage. This study confirmed that catechin, which is naturally found in tea leaves, could be used as an ozone protectant. The protective role of catechin on chlorophyll contents and antioxidant systems at the vegetative stage attributed to maintaining rice yield under ozone stress. Graphical abstract.