Effects of night warming and soil copper contamination on copper retention in wheat

Grain production in China is subject to the stresses of copper (Cu) contamination in agricultural soils and asymmetric climate warming; it is vital to understand the effects of these dual pressures on crop growth and production. Since asymmetric climate warming and soil Cu accumulation potentially affect wheat production in China, it is important to analyze the effects of night warming on the uptake and distribution of Cu in wheat under Cu pollution stress. A pot experiment was conducted during the 2018-2019 wheat growth season on the Experimental Farm of the Henan University of Science and Technology (34°35N, 112°24E), an agricultural area with an annual average temperature of 14.86℃ and annual average precipitation of 600 mm. The experiment had two temperature treatments (a control group and night warming under a passive night warming system) and two levels of Cu pollution (6 mg·kg^-1control and 155 mg·kg^-1Cu pollution). The Cu-polluted soils in the pots were collected from a Cu single factor contaminated site at the Kaiyuan Campus Farm of Henan University of Science and Technology. The crop responses (vs. Luohan 11) to night warming and Cu contamination with respect to yield, biomass of different aboveground tissues, and content, accumulation, and translocation coefficients of Cu in the aboveground tissues were investigated. The results showed that night warming significantly increased the crop straw, spike, aboveground, and total biomasses by 25.1%, 21.3%, 22.7%, and 22.3%, respectively, and could alleviate the inhibition of Cu pollution on wheat growth. Night warming significantly increased the straw Cu content by 26.3% in the control group, but significantly decreased the straw Cu content by 13.9% in the Cu pollution groups. In the control group, night warming significantly increased Cu accumulation by 14.7%-56.5% in the straw, spike, aboveground, and whole plant. In the Cu pollution groups, night warming increased Cu accumulation by 12.1%-22.8% in the roots, spikes, and whole plant. Night warming and Cu pollution affected the migration and utilization of Cu in different tissues. Night warming significantly increased the Cu translocation coefficient from root to stem and decreased the stem to leaf and stem to spike Cu translocation coefficients in the control. Night warming significantly decreased Cu transport from root to stem, did not affect Cu transport from stem to leaf, and increased Cu transport from stem to spike in the Cu pollution groups. Cu pollution changed the response law of wheat Cu absorption and utilization as it related to night warming. This study illustrated that night warming improved wheat production and alleviated the harmful growth-related effects of Cu stress, however, if increased potential risk of Cu pollution on grain crop quality.