Canola responds differently to nitrogen forms under temperature and carbon dioxide conditions
摘要
Climate change components, such as temperature and carbon dioxide (CO2), can affect plant growth; however, few studies have considered the combined effects of these factors and nitrogen on plant growth and development. In this study, the effects of two temperature regimes (LT, lower temperatures; 22/18 °C, on average 20.7 °C; HT, higher temperatures; 28/24 °C, on average 26.7; 16 h light/8 h dark), two CO2 concentrations (ACO2, ambient CO2; 400 ± 10 μmol mol−1; ECO2, elevated CO2; 700 ± 10 μmol mol−1), and three nitrogen supplements (no extra nitrogen as control (only 70 mg); 130 mg of nitrate; 130 mg ammonium) were studied on canola (Brassica napus L.) — an important oilseed crop in Canada and worldwide. Plants were grown under twelve experimental conditions for three weeks, following an initial week of growth under LT and ACO2. Plant growth and physiological traits were measured. HT decreased plant biomass but increased glycine. ECO2 increased water-use efficiency. Nitrate increased leaf area and number, nonphotochemical and photochemical quenching and aspartic acid, whereas ammonium increased specific leaf mass and threonine. In combination, LT at ECO2 increased root mass in plants without supplemental nitrogen whereas ACO2 increased total mass in the nitrate-treated plants, and ECO2 decreased it in the ammonium-treated plants; HT at ECO2 increased shoot:root mass ratio of plants without supplemental nitrogen; LT at ACO2 increased maximum quantum yield of PSII and chlorophyll a:b ratio, and HT at ACO2 increased alanine in the ammonium-treated plants. In conclusion, nitrate played a more significant role than ammonium in shaping plant responses to climate change factors.