The effect of heat wave, elevated CO2 and N deprivation on growth of Brassica napus

Abstract

Heat waves, broadly defined as a period of consecutive days where conditions are hotter than normal, including seasonally extreme events, are predicted to increase in frequency and severity with global climate change. The interactive effect of simulated summertime heat wave, elevated atmospheric CO2 and nitrogen deprivation as well as the recovery following treatments were investigated in this study with agronomically important crop Brassica napus (summer rapes). The experiment was conducted in closed-top growth chambers under controlled environment. The heat wave (HW) treatment (+12 °C of ambient air temperature) either at ambient or elevated CO2 (400 and 800 μmol mol-1) and under adequate or deprived soil N (160 and 60 kg ha-1) was applied at 13 BBCH growth stage for 7 days. A 7-day long recovery period under ambient climate (i.e. temperature and CO2, AC) conditions, upon relief of the heat wave, was also applied. Both the above and the below-ground growth responses of Brassica napus to HW treatment were dependent on CO2 and N availability, though in somewhat different manner. Surprisingly, under adequate N conditions, the HW treatment had a positive effect on leaf area (LA) and shoot dry weight (DW) and this positive effect was additionally reinforced by elevated CO2 (HWC treatment). Under N deprivation, however, the above, especially, and the below-ground growth responses were to a large extent lower and did not differ between climate conditions (AC, HW and HWC) nor after the treatments neither after the recovery. After the 7-day recovery period, additional stimulating effect of elevated CO2 on the above-ground growth response to HW treatment, under adequate N conditions, disappeared, although both LA and shoot DW, under HW and HWC treatments, were significantly higher, compared to those grown under AC conditions. [...]