2. Planting O 3 -resistant plants
Different plants have different sensitivity under high O 3 levels. Thus, O 3 -resistant
genotypes can be selected, reproduced, and/or genetically modified by adding
O 3 -resistant genes. Such genes were already discovered for rice and soybean (Frei
et al. 2010; Gillespie et al. 2011). Additionally, there are a large number of studies on
the sensitivity of plants to O 3 . For example, Feng et al. (2018) demonstrated that a lot
of O 3 sensitivity variation for different woody plants can be explained by interspecific variation in LMA. Thus, ozone-tolerant plants can be chosen based on these
rules and planted in certain O 3 -rich areas to maintain their vegetation and to reduce
the damage under high O 3 levels.
3. Ozone uptake through plants
Typically, ozone enters a plant through its leaf stomata, after which plants absorb
O 3 and reduced O 3 content in the ambient air. This ability of plants to purify air is an
important property that can be used at urban, ecological, and environmental planning
and landscaping. However, plant-derived BVOCs can also participate in O 3 formation. Thus, high O 3 uptake and low-BVOC emission plants should be considered to
efficiently control O 3 levels.
4. Application of chemical protective agents at specific phenological stages
Ozone-caused damage to plants could be decreased or prevented by application of
antioxidants (e.g., glutathione, ascorbic acid, antiozonant ethylenediurea (EDU),
etc.) (Feng et al. 2010; Manning et al. 2011). Such chemical agents are indeed
widely used in the USA and many European countries to protect crops against high
ambient O 3 . However, the toxicity of EDU in the food chain is yet to be extensively
tested, and the phytotoxicity can happen at high doses of EDU (Manning et al.
2011). Thus, most effective approach is to apply such agents at specific phenological
stages, such as grain filling in both soybeans and wheat, during rice tillering, etc. It is
necessary to apply these chemical protective agents to protect crops from production
in high O 3 concentration areas. However, further testing of EDU toxicity and
its impact on different crops are required through the field experiment.
⁄
ä
Fig. 7.11 (continued) 95% bootstrapped confidence intervals. Number of measurements and papers
are shown in parentheses, whereas mean elevated O 3 concentration and control O 3 concentration in
square brackets are given along the y-axis. The following abbreviations were used to represent
parameters studied: φPSII effective quantum yield of photosystem II, APX ascorbate peroxidase,
AsA ascorbic acid, Car carotenoid, CAT catalase, DHAR dehydroascorbate reductase, GR glutathione reductase, LMA leaf mass per area, MDA malondialdehyde, MDAR monoascorbate reductase,
SOD superoxide dismutase activity, TAC total antioxidant capacity, WUE water-use efficiency.
(This figure was adapted from Li et al. (2017b) with permission by John Wiley and Sons)
7 Contribution of Atmospheric Reactive Nitrogen to Ozone Pollution in China
151
Different plants have different sensitivity under high O 3 levels. Thus, O 3 -resistant
genotypes can be selected, reproduced, and/or genetically modified by adding
O 3 -resistant genes. Such genes were already discovered for rice and soybean (Frei
et al. 2010; Gillespie et al. 2011). Additionally, there are a large number of studies on
the sensitivity of plants to O 3 . For example, Feng et al. (2018) demonstrated that a lot
of O 3 sensitivity variation for different woody plants can be explained by interspecific variation in LMA. Thus, ozone-tolerant plants can be chosen based on these
rules and planted in certain O 3 -rich areas to maintain their vegetation and to reduce
the damage under high O 3 levels.
3. Ozone uptake through plants
Typically, ozone enters a plant through its leaf stomata, after which plants absorb
O 3 and reduced O 3 content in the ambient air. This ability of plants to purify air is an
important property that can be used at urban, ecological, and environmental planning
and landscaping. However, plant-derived BVOCs can also participate in O 3 formation. Thus, high O 3 uptake and low-BVOC emission plants should be considered to
efficiently control O 3 levels.
4. Application of chemical protective agents at specific phenological stages
Ozone-caused damage to plants could be decreased or prevented by application of
antioxidants (e.g., glutathione, ascorbic acid, antiozonant ethylenediurea (EDU),
etc.) (Feng et al. 2010; Manning et al. 2011). Such chemical agents are indeed
widely used in the USA and many European countries to protect crops against high
ambient O 3 . However, the toxicity of EDU in the food chain is yet to be extensively
tested, and the phytotoxicity can happen at high doses of EDU (Manning et al.
2011). Thus, most effective approach is to apply such agents at specific phenological
stages, such as grain filling in both soybeans and wheat, during rice tillering, etc. It is
necessary to apply these chemical protective agents to protect crops from production
in high O 3 concentration areas. However, further testing of EDU toxicity and
its impact on different crops are required through the field experiment.
⁄
ä
Fig. 7.11 (continued) 95% bootstrapped confidence intervals. Number of measurements and papers
are shown in parentheses, whereas mean elevated O 3 concentration and control O 3 concentration in
square brackets are given along the y-axis. The following abbreviations were used to represent
parameters studied: φPSII effective quantum yield of photosystem II, APX ascorbate peroxidase,
AsA ascorbic acid, Car carotenoid, CAT catalase, DHAR dehydroascorbate reductase, GR glutathione reductase, LMA leaf mass per area, MDA malondialdehyde, MDAR monoascorbate reductase,
SOD superoxide dismutase activity, TAC total antioxidant capacity, WUE water-use efficiency.
(This figure was adapted from Li et al. (2017b) with permission by John Wiley and Sons)
7 Contribution of Atmospheric Reactive Nitrogen to Ozone Pollution in China
151