ABSTRACT
The frequency of drought will increase under further warming. The increase in atmospheric CO2 concentration, along with more frequent drought, will affect crop growth. We examined the changes of cell structure, photosynthetic physiology, antioxidant enzymes, osmotic regulatory substances, and yield of foxtail millet (Setaria ita-lica) leaves under different CO2 concentrations (ambient air CO2 concentration and ambient atmospheric CO2 concentration + 200 µmol·mol-1) and water treatment (soil moisture content maintained at 45%-55%, and 70%-80% of field capacity, representing mild drought and normal water condition, respectively). The results showed that elevated CO2 concentration increased the number of starch grains, the area of single starch grains, and the total area of starch grains in the chloroplast of millet mesophyll cells. Under mild drought condition, elevated CO2 concentration increased net photosynthetic rate of millet leaves at the booting stage by 37.9%, but did not affect water use efficiency at this stage. Elevated CO2 concentration increased net photosynthetic rate and water use efficiency of millet leaves under mild drought condition at the filling stage by 15.0% and 44.2%, respectively. Under mild drought condition, elevated CO2 concentration increased the content of peroxidase (POD) and soluble sugar in millet leaves at the booting stage by 39.3% and 8.0%, respectively, but decreased proline content by 31.5%. It increased the content of POD in millet leaves at the filling stage by 26.5% but decreased the content of MDA and proline by 37.2% and 39.3%, respectively. Under mild drought condition, elevated CO2 concentration significantly increased the number of grain spikes by 44.7% and yield by 52.3% in both years compared with normal water condition. The effect of elevated CO2 concentration on grain yield under mild drought conditions was higher than that under normal water condition. Under mild drought conditions, elevated CO2 concentration increased leaf thickness, vascular bundle sheath cross-sectional area, net photosynthetic rate, and water use efficiency of millet, improved the antioxidant oxidase activity, and changed the concentration of osmotic regulatory substances, alleviated the nega-tive effect of drought on foxtail millet, and finally increased the number of grains per ear and yield of foxtail millet. This study would provide a theoretical basis for millet production and sustainable agricultural development in arid areas under future climate change.
Subject(s)
Setaria Plant , Setaria Plant/physiology , Carbon Dioxide , Antioxidants , Droughts , Proline , Starch/pharmacologyABSTRACT
Rational application of organic fertilizers is an effective approach to improve soil fertility, crop yield, and zero growth of chemical fertilizer in agricultural production. The rice variety 'Shennong9816' was planted in Shenyang, Liaoning Province, under seven different treatments: zero nitrogen fertilizer (CK), low nitrogen, 150 kg·hm-2(LN), medium nitrogen, 240 kg·hm-2 (MN), high nitrogen, 330 kg·hm-2(HN), medium nitrogen with replacement of chemical N by 10% organic manure (OMN10), medium nitrogen with replacement of chemical N by 20% organic manure (OMN20), and medium nitrogen with replacement of chemical N by 30% organic manure (OMN30). The effects of different treatments on photosynthetic rate, nitrogen absorption, nitrogen use efficiency, and yield were examined and the optimal fertilization scheme was determined. The results showed that the photosynthetic rate, biomass and yield were increased with the increases of nitrogen application rate, while the nitrogen use efficiency was decreased significantly. Compared with the MN treatment, the photosynthetic rate of OMN10 and OMN20 in filling stage was increased by 22.9% and 9.9%, respectively. The yield of OMN20 was increased by 3.8% compared to that of MN. The nitrogen agronomic efficiency and physiological efficiency of OMN20 were significantly improved by 8.1% and 13.3%, respectively. Moreover, the nitrogen agronomic efficiency and physiological efficiency of OMN20 were improved by 27.2% and 37.2% compared with the HN treatment. Thus, we concluded that the organic fertilizer replacement treatment could conserve soil fertility, achieve high yield and high nitrogen use efficiency, while reduce chemical nitrogen fertilizer application. The OMN20 treatment was recommended as a fertilizer application model due to its superior performance among the seven treatments.