Effects Of Nitrogen Application On Foliar Photosynthesis And Plant Yield Of Spring Wheat Under Elevated Atmospheric Co 2 Concentration

Using the open-top chamber controller, spring wheat (Triticum aestivum L.) were grown in either elevated CO₂(760μmol·mol-1) or ambient CO₂(400μmol·mol-1) concentration, and at 3 nitrogen nutrition levels (0, 100, 200 mg·kg-1 soil means N0,N1,N2), there were 9 treatments in this potted experiment, repeated ten times. The plant height, net photosynthetic rate, transpiration rate, water use efficiency, stomata conductance, yield and yield components factors, chlorophyll content were measured. The main conclusions of the study are summarized as follows:(1)The foliar chlorophyll content decreased under elevated atmospheric CO₂ concentration, but sufficient nitrogen application could relieve this adverse effect. The foliar chlorophyll content increased, and the ratio between chlorophyll a and b was optimized in high nitrogen wheat leaves, to increase the light energy use efficiency of chloroplast. The photosynthesis down-regulation appeared in middle and low nitrogen wheat leaves, but disappeared in high nitrogen leaves under elevated atmospheric concentration. The net photosynthesis(Pn), stomatal conductance(Gs), transpiration(Tr) were increased with the increase of nitrogen application rate, it increased for 57.1%,94.1% and 70.4% in high nitrogen spring wheat under elevated atmospheric CO₂ concentration. However, the intercellular CO₂ concentration(Ci) and water use efficiency(WUE) were decreased and then increased with the increase of nitrogen application rate. The Pn, Ci and WUE of spring wheat leaves under elevated atmospheric CO₂ concentration were higher than the ambiment atmospheric CO₂ concentration significantly, the average increased ranges were 36.8%,74.0% and 102.7% in three nitrogen application rates reapectively. In Jointing stage, the photosynthetic acclimation was not happened in high-N wheat leaves which grown under elevated atmospheric CO₂ concentration were lower than the ambiment treatments significantly.(2)The height of N0, N1 and N2 wheat increased by 1.6cm, 1.9cm and 2.0cm in the jointing stage, 2.7cm, 3.1cm and 2.6cm in the heading stage, 4.0cm, 4.8cm and -0.6cm in the harvest stage respectively.The increment extent of dry weight was highest in the middle nitrogen wheat leaves, but lowest in high nitrogen level. Compared to ambient CO₂ concentration, the ear length of low and high nitrogen wheat were increased for 10.0% and 8.5% in heading stage under elevated atmospheric CO₂ concentration. In harvest stage, the ear length of middle nitrogen wheat under elevated atmospheric CO₂ concentration was higher than ambient CO₂ treatment, its increased by 13.3%. Both 1000-grain weight and grain weight per spike was increased in low and middle nitrogen level and elevated atmospheric CO₂ concentration, 1000-grain weight increased by 7.8% and 2.1%, grain weight per spike increased by 17.0% and 33.4%.