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Effects of Atmospheric NH3 on Root Canopy Characteristics and Nitrogen Use Efficiency of Wheat and Maize

Author: LiJing
Tutor: LiShiQing
School: Northwest University of Science and Technology
Course: Ecology
Keywords: Maize Winter Wheat NH3 Concentrations N Using Efficiency Physiology Indexes Open Top Chambers
CLC: S513
Type: Master's thesis
Year: 2009
Downloads: 27
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Abstract


Effects of elevated atmospheric NH3 on plants receive much attention at home and abroad.Foreign scientists have done lots of work on this domain.However much of our current knowledge of the effects of NH3 on higher plants were predominantly derived from studies conducted in Europe,and the study subjects mainly focus on forest and grassland vegetation.As a result,few studies on atmospheric NH3 were done in agro-ecosystem.In recent years,more and more scientists have paid much attention on studies of atmospheric NH3 in China,but there is seldom information to consult.Pot experiments（using corn and winter wheat as indicators）were carried out in Open Top Chambers（OTCs）to study the effects of atmospheric NH3 concentrations on growth and development,photosynthesis characteristics,nutrient distribution and grain yield of crops with different N efficiency genotypes under different N level.In this study,there were involved in three factors:two NH3 concentrations（elevated NH3 1000nL/L and 10nL/L NH3）,two crops（corn and winter wheat）, and two N levels.The experiment adopted complete design scheme and there were total eight treatments.The experiment was divided into two sub-experiments,e xperiment I-winter wheat planted in soil and experimentⅡ-maize planted in soil.The main results showed as follows:1.Elevated NH3 had a significant influence（p＜0.05）on Pn and Gs of the two winter wheat cultivars（XY6 and CH58）and the influence was related to cultivars and N levels.The effect law of elevated NH3 on Chlorophyll content for two wheat varieties was similar with Pn. However,the influence degree was smaller than that on Pn and Gs.In Maize experiment, under high N medium,Pn of SY21 and HD4 decreased as atmospheric NH3 concentration increased.However,the value of Pn increased as NH3 concentration increased under low N medium.Compared with 10nL/L atmospheric NH3,the Gs value of SY21 and HD4 increased, and the influence on HD4 was higher compared with SY21.2.The value of Fv/Fm and Fv/F0 of the two winter wheat cultivars was not significantly affected by elevated atmospheric NH3 concentration in the high N treatment.Under low N treatment,Chlorophyll fluorescence parameters increased as atmospheric NH3 increased.The leaves Fv/Fm and Fv/F0 significantly increased in the high N treatment under both NH3 concentrations.But the effect of atmospheric NH3 density on leaf Fv/Fm and Fv/F0 of maize was lack of regularity.3.The effect of elevated atmospheric NH3 on C and N metabolites was significant （p＜0.05）.However,it depended on medium N level.Both of SY21 and HD4,the free amino acid amounts increased as atmospheric NH3 concentration increased.The increasing extent reached 33.9%and 21.7%in the high N treatment and 34.0%,23.9%for low N medium, respectively.Under high N medium,compared with 10nL/L atmospheric NH3 concentrations, soluble sugar content of SY21 and HD4 increased,and the increasing extent of HD4 was wider compared with SY21.Under low N medium,the effect of elevated atmospheric NH3 on soluble sugar was not significant.The correlation analysis between free amino acids and soluble sugar showed that leaf free amino acids and soluble sugar content of SY21 and HD4 were a positive correlation,and the SY21 correlation coefficient was higher.These results showed that after plant N nutrition improvement,while increases the N assimilation,also obviously increased the C assimilation.4.Under low N treatment,elevated atmospheric NH3 significantly improved the shoot biomass and grain yield of the two wheat cultivars.The plant height and root/shoot radio decreased as atmospheric NH3 increased under high N medium.The plant height and root/shoot radio were significantly increased（p＜0.05）compared to 10nL/L NH3 under low N medium.The effect of elevated NH3 on grain yield of XY6 was not significant.However,it significantly improved grain yield of CH58（p＜0.05）.In Maize treatment,under high N medium,the effect of inhibition of elevated NH3 on root was smaller than that on shoot,so leading to the value of R/S increasing,especially to SY21.5.Under low N medium,elevated NH3 improved N absorption of wheat shoot,and the effect on XY6 was more than CH58.N uptake of plant different organs was increased as NH3 increased and high Nmedium,but the increasing extent depended on wheat cultivars.N Use Efficiency of XY6 and CH58 decreased as atmospheric NH3 increased.Elevated NH3 decreased the NHI of XY6 and CH58,and the decreasing extent were 7.27%and 6.25%, respectively.However the effect was not significant.6.These results showed that increased atmospheric NH3 inhibited crop growth and metabolism in high N medium,especially to high N efficiency genotype.However,under low N medium,elevated NH3 concentration significantly improved the crop growth and metabolism.All these results fully proved the basic assumptions that the absorbed atmospheric NH3 by plants can improve crop N nutrition growing in low N medium,but the result of being more significantly positive effect on low N efficiency genotypes still needs further study.

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