Abstract
Three wheat (Triticum aestivum L.) cultivars [HD 2987 (ozone (O3) sensitive), PBW 502 (intermediately sensitive) and Kharchiya 65 (O3 tolerant)] with known sensitivity to O3 were re-evaluated using ethylenediurea (EDU; 400 ppm) to ascertain the use of EDU in determiningO3 sensitivity under highly O3-polluted tropical environments. EDU treatment helped in improving the growth, biomass, photosynthetic pigments and the antioxidative defense system of all the wheat cultivars. Under EDU treatment, PBW 502 retained more biomass, while HD 2987 showed better performance and ultimately the greatest increment in yield. Cultivar Kharchiya 65 also showed a positive response to EDU as manifested with an increase in pigment contents, total biomass and enzymatic antioxidants; however, this increment was comparatively lower compared to the other two cultivars. The results indicated that EDU did not have many physiological effects on cultivars but helped in counteracting O3 primarily by scavenging reactive oxygen species and enhancing the antioxidative defense system where superoxide dismutase emerged as the major responsive biochemical parameter against ambient O3. The observed results clearly indicated that differential O3 sensitivity in three wheat cultivars established by the previous study is in accordance with the present study using EDU as a sensitivity tool, which is an easy and efficient technology in comparison to chamber and Free-Air Carbon dioxide Enrichment (FACE) experiments although its mechanistic understanding needs to be further validated.
Highlights
Tropospheric ozone (O3 ) is a spatially and temporally dynamic air pollutant as well as a powerful greenhouse gas [1]
The maximum a threshold of 40 ppb (AOT 40) value of 2939.4 ppb h was observed in the month of March and the cumulative AOT 40 value observed for the ambient O3 environment was 9168.21 ppb h during the experimental period
At 60 days after germination (DAG), the plant height increased maximally by 14.4% in HD 2987, while it increased least in Kharchiya 65, by 6.2%.The number of tillers was maximally increased in PBW 502 by 57.1% and it increased least in Kharchiya 65, by 31.8%, while the total biomass increased by 34.3% in PBW 502 followed by 22.3%
Summary
Tropospheric ozone (O3 ) is a spatially and temporally dynamic air pollutant as well as a powerful greenhouse gas [1]. This increasing air pollutant of the lower atmosphere has negatively influenced food security, thereby causing tremendous loss to the growth and productivity of various crops. A distinct correlation exists between the peak O3 concentration and major crop growing season, resulting in high yield losses [4]. Global yield losses due to O3 in major crops such as wheat, rice, maize and soybean were 4–15%, 3–4 %, 2–5% and 5–15%, respectively [4,5]; for the year 2000, it was found that 40% of these losses were from India and China [4]. As per the projection of a new study, a 40% increase in O3 concentration is expected in Plants 2019, 8, 80; doi:10.3390/plants8040080 www.mdpi.com/journal/plants
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