Abstract
ABSTRACT Maize is an important C4 crop and how it will respond to elevated atmospheric carbon dioxide and ozone levels is not well documented. To understand how the growth and nutritional quality of maize will be affected under elevated carbon dioxide (CO2) and tropospheric ozone (O3) interaction, a field experiment was conducted under free air O3 and CO2 enrichment rings (FAOCE) growing HQPM-1 and PMH-1 maize cultivars at New Delhi, India. Each cultivar was exposed to ambient and elevated CO2 (559 ppm) alone and along with ambient and elevated O3 (71.8 ppb) throughout the growing period. Elevated CO2 (EC) significantly increased the leaf area index (10.8–22.5%), chlorophyll (11.2–17.3%) and photosynthetic rate (12.1–16.5%) in the two cultivars over the ambient. O3 exposure of 27 ppm hr (AOT4O) under elevated O3 (EO) treatment led to a significant decline in yield (p < 0.01) by 9.2% in HQPM-1 and 9.8% in PMH-1. Under elevated CO2 the increase in grain yield was higher under HQPM-1 (25.4%) as compared to PMH-1 (9.04%). The protein content increased under EO (8.1–12.5%) and decreased under EC (13.4–13.6%) in the two maize cultivars due to yield dilution effect. Lysine, phosphorus and potassium content of the grain significantly decreased in both the cultivars under elevated CO2. Carbohydrate and amylose concentrations in grains increased (9.9–15.5%) under EC and decreased (10.8–16.7%) under EO, however, no significant change in yield, protein, amylase, carbohydrate, lysine, potassium and phosphorus was observed under the interaction treatment ECO as compared to the ambient. After two years of study we could conclude that elevated CO2 (559 ppm) was able to offset the negative effect of elevated O3 (71 ppb) on grain yield by 11.2% in PMH-1 and by 18.8% in HQPM-1 without significantly affecting the grain quality in both the maize cultivars.
Highlights
Climate change and air pollution are increasing threats to agriculture production and food security (Porter et al, 2014; Tai et al, 2014)
The photosynthetic rates (Pn) in the interactive treatment elevated CO2 and O3 (ECO) increased by 11.9-12.4% for HQPM-1 and by 10.9–18.5% for PMH-1 over elevated O3 alone and was found to be at par with the ambient
In our study the presence of elevated CO2 increased the carbon uptake and yield of maize, but the increased carbohydrates in the grain led to a decline in the nutrient content (P, K & crude protein) due to the dilution effect and lowered the grain quality
Summary
Climate change and air pollution are increasing threats to agriculture production and food security (Porter et al, 2014; Tai et al, 2014). Increasing concentration of tropospheric O3 in India, especially in the Indo-Gangetic Plains (IGP) is of major concern as it poses a threat to the quality and productivity of crops (Singh and Agrawal, 2017) and may reach 70 ppb by 2050 in South Asia (IPCC, 2014) Apart from this most of the studies on the impact of tropospheric O3 on crops have been conducted in Europe and America (temperate regions). Keeping in view the contrasting response obtained in C4 crops under elevated CO2, the present study was carried out with the aim to assess the impact of elevated CO2 and tropospheric O3 separately as well as in combination on the growth, yield and nutritional quality of maize under free air O3 and CO2 enrichment
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