The improvement of nitrogen use efficiency of cucumber plant by increasing atmospheric carbon dioxide and root temperature in a greenhouse
Low atmospheric CO2 concentration ([CO2]) and root temperature are two critical adverse factors that depress the growth and nutrient absorption of greenhouse vegetables in cold winters. Two independent pot experiments were designed to investigate the effects of increasing [CO2] and root temperature on the nitrogen (N) absorption and N use efficiency (NUE) of cucumber, respectively. The elevated [CO2] experiments were carried out in three open-top chambers (OTCs). The [CO2] in each OTC was set at 400 (C1), 625 (C2), and 1200 (C3) μmol mol‑1, respectively. When the [CO2] was increased from C1 to C3, the increase in dry weight (D.W.) was 109.5 and 117.0% in N2 (14 mM) and N3 (21 mM) treatment, respectively. Although there was a trend of decrease in the N concentration ([N]) when [CO2] was increased, the N accumulation by the above-ground plant was still increased. The NUE was increased by 8.3~10.9 percentage points when [CO2] was increased from C1 to C3. In the improved root temperature experiments, the average root temperature in the whole growth period of cucumber was 19.7°C in the warmed treatment (T2). In contrast, it was only 11.6°C in the un-warmed treatment (T1). Improving the root temperature increased the D.W. of the above-ground plant by 70.9 and 91.7%, respectively. The [N] of the above-ground plant was increased by 15.3 and 28.2% in N2 and N3 treatment, respectively. The improvement of the NUE was 11.7~18.0 percentage points by elevating the root temperature. These results indicate that both increasing [CO2] and root temperature could promote the N uptake and NUE of cucumber, but the mechanisms are different. The increases in NUE mainly relied on the increase of the D.W. by elevated [CO2], whereas both the accumulation of biomass and increased [N] contributed to the higher NUE by increasing root temperature.
Li, X., Gruda, N., Dong, J. and Duan, Z. (2021). The improvement of nitrogen use efficiency of cucumber plant by increasing atmospheric carbon dioxide and root temperature in a greenhouse. Acta Hortic. 1320, 139-148
Cucumis sativus, dry weight, nitrogen uptake, nitrogen concentration, open-top chamber, pot experiment