Heliyon (Aug 2019)
The effects of elevated CO2 and elevated O3 exposure on plant growth, yield and quality of grains of two wheat cultivars grown in north India
Abstract
Global food security is challenged by increasing levels of CO2, O3 and temperature trough their impacts on production and grain quality of wheat, one of the major C3 crops and staple food across the world. The present study was conducted to assess the effects of elevated levels of CO2 (EC; 550 ppm) and tropospheric O3 (EO; 70 ppb) as well as of combined interactive treatment [EC X EO; ECO] on plant growth, yield and grain quality of two wheat cultivars (HD-2967 and C-306) grown during 2016–17 and 2017–18 using free air ozone and carbon dioxide enrichment (FAOCE) facility under field conditions. Individually, EC, increased leaf area index (LAI; 15.9–28.2%), photosynthetic rate (Pn; 11.4–20.3%) and yield (8.2–20.9%) whereas EO declined LAI (5.1–12.5%), Pn (2.8–11.8%) and yield (2.2–14.2%) over ambient conditions (Amb: 405.2 ppm CO2 and 30.7 ppb O3). Under ECO condition, EC increased LAI (2.2–17.1%), Pn (2.8–17.6%) and grain yield parameters (4.4–24.3%) across the cultivars in both years, but reduced the positive effects of EO on quality as compared to Amb. Dilution effect of increased yield under EC condition have reduced total protein, micro- and macro-nutrient concentrations whereas EO increased them notably compared to Amb. Starch in grains increased under EC but reduced under EO as compared to Amb. AOT40, the sum of averaged difference of O3 h−1 concentration beyond 40 ppb for 7 hours (31233 ppb h−1) in FAOCEs rings during the crop growth period led to reduction in average grain yield of HD-2967 and C-306 by 11.6 and 8.5% or by 1.6 and 1.3% yield loss per ppb increase of O3, respectively. The growth, yield and quality parameters of both wheat cultivars responded similarly but to different extent to all treatments. EC was able to offset the negative effects of EO on yield and yield components only, but not those concerning the quality of grains. To stabilize global food security, precursor gases forming tropospheric ozone must be constrained.
