| Water resource is limited in the desert oasis area of northwest China. In order to improvethe water use efficiency in this area, water-saving methods have been widely used. Alternatepartial rootzone irrigation was developed recently and was confirmed to be a successfulwater-saving irrigation regime. In this thesis, maize for seed under APRI was studied by potexperiment in green house, pot experiment in the semi–field and field experiment to get thesoil water content,weather parameters,morphology parameters and physiology parameters ofmaize for seed plants using advanced equipment such as TDR,ANCA-SL Elemental Analyserand20-20Tracer Mass Spectrometer et al. According to the findings in experiments, a revisedJarvis model was successfully set to simulate the stomatal conductance under APRI. In thisthesis, we got several results as shown in following:(1) The physiological basis for the advantage of alternate partial root-zone irrigation(APRI) over common deficit irrigation (DI) in improving crop water use efficiency (WUE)was studied in this thesis. Leaf gas exchange characteristics and photosynthetic CO2–responseand light–response curves for maize (Zea mays L.) leaves exposed to PRI and DI wereanalysed under three N-fertilization rates, namely75,150, and300mg N kg-1soil.Measurements of net photosynthetic rate (An) and stomatal conductance (gs) showed that,across the three N-fertilization rates, the intrinsic WUE was significantly higher in APRI thanin DI leaves. Analysis of the CO2–response curve revealed that both carboxylation efficiency(CE) and the CO2-saturated photosynthetic rate (Asat) were significantly higher in PRI than inDI leaves across the three N-fertilization rates; whereas the N-fertilization rates did notinfluence the shape of the curves. The enhanced CE and Asat in the PRI leaves wasaccompanied by significant decreases in carbon isotope discrimination (Δ13C) andbundle-sheath cell leakiness to CO2(Φ). Analysis of the light–response curve indicated that,across the three N-fertilization rates, the quantum yield (α) and light-saturated grossphotosynthetic rate (Amax) were identical for the two irrigation treatments; whilst theconvexity (κ) of the curve was significantly greater in APRI than in DI leaves, which coincided with the greater CE and Asat derived from the CO2–response curve at aphotosynthetic photon flux density of1500μmol m-2s-1. Collectively, the results suggest that,in comparison with the DI treatment, APRI improves photosynthetic capacity parameters CE,Asat, andκof maize leaves and that contributes to the greater intrinsic WUE in those plants.(2) The effects of alternate partial root-zone drying (APRI) irrigation as compared withconventional deficit irrigation (DI) and full irrigation (FI) on leaf nitrogen (N) accumulationwere investigated in maize (Zea mays L.) grown under three N-fertilization rates. The resultsshowed that neither irrigation nor N-fertilization treatments influenced shoot biomass andplant leaf area; while APRI plants had the highest root biomass and root to shoot ratiocompared to DI and FI plants. Increase of N rate significantly increased leaf N accumulation;across the N-fertilization rates, APRI and FI plants accumulated significantly greater amountof N in leaves than did DI plants. Leaf15N decreased significantly with increasingN-fertilization rate, and was significantly higher in PRD and FI than in DI plants. Water useefficiency (WUE) was the highest in APRI, followed by DI and the lowest in FI; whileN-fertilization rate had no effect on WUE. It was concluded that an enlarged root system andan enhanced soil N availability under APRI might have contributed to the greater Naccumulation in maize leaves.(3) The effects of Alternate partial root zone Irrigation (APRI) as compared with deficitirrigation (DI) and full irrigation (FI) on pH, ABA, nitrate and other ion concentrations inxylem sap using 'root pressure' method51days after treatment (DAT) and their relationshipswith stomatal conductances (gs) were investigated in maize plants (Zea mays L.) grown underthree N-fertilization rates. The results showed that response of pH in xylem sap to increasingN concentration from deficient to sufficient to supra-optimal is biphasic, which decreasesfrom deficit to optimal N, and then increase again as N increase further. The ABAconcentration in the xylem sap showed the same trend with pH with the increase of Nconcentration in xylem sap. Increasing the nitrate (N) concentration above optimal (N3level)decreased stomatal conductance compared with treatments in N2and N1level in maizeseedlings (Zea mays L.) growing in DI and APRI, but not for the treatment of FI, whichindicate that the pH,ABA and N signals might interact together to affect the gs. Across Nlevels, the value of gs for FI is the highest, followed by DI and APRI. Through analyzing therelationship between comprehensive component in xylem sap and gs, we found that exceptABA, calcium might be also a root-to-shoot signaling in controlling stomatal conductance.(4) There were significant linear relationships between CCI and N concentration inmaize leaves, as well as photosynthesis capacity. With the increase of CCI and Nconcentration in leaves, the relative maximum stomatal conductance for leaves (gmax Rel) was significantly increased. gmax Reldecreased gradually with the increase of differences betweenleaf and air temperature (Tl-Ta),. When the value of (Tl-Ta) was-2℃, the gmax Relcould get tomaximum stomatal conductances during the growing seasons. From the regression analysis,we could find there were positive relationships between (Tl-Ta) and Q, but (Tl-Ta) werenegatively related to VPD and Ψs(5) With adding the CCI parameter related to physiology situation of leaves and Ψsparameter relating to hydraulic and chemical signaling in Jarvis model, the stomatalconductances of maize plants under APRI were successfully simulated. The E1and d1formodified Jarvis model was improved30%and6%, respectively, compared with the originalJarvis model.In conclusion, APRI has the potential to be applied in the arid area of northwest Chinafor saving water and increasing WUE. With adding the average soil water potential for wetand dry compartment of APRI representing the combined function of hydraulic andnon-hydraulic signaling and CCI which represent the physiology situation of leaves, themodified Jarvis model improved the accuracy of simulated stomatal conductances underAPRI.
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