Differences Of Nitrogen Utilization Efficiency And Its Physiological Mechanism In Different Wheat Related Species

The nitrogen utilization efficiency of wheat is regulated by genetics, ecologicalenvironment and cultural measure. Selected efficient genotype was one of most effectivemeasures to increase nitrogen uptake and utilization efficiency in wheat. So it is importantto study the difference of NUE and its physiological mechanism in different wheat relatedspecies for selecting genotype. Ten wheat materials including four diploid speciesT.boeoticum, T.monococcum, Ae.squarrosa and S.cereale, three tetraploid speciesT.dicoccoides, T.dicoccum and T.durum, two hexaploid cultivars Yangmai 158 and Ningmai9, and one octoploid specie Triticale were used. The pot experiment was carded out tostudy the difference of NUE and its physiological mechanism in different wheat relatedspecies. The main results were summarized as follows:1. There were significant differences in grain yield and NUE parameters among tenrelated species. The results showed that there were significant differences in grain yield andNUE parameters among ten related species. The spikes per plant of diploid and tetraploidspecies were higher, but the kernels per spike, 1000 kernels weight and grain yield werelower than those of hexaploid and octoploid species. The NYE, NHI and NPE of diploidand tetraploid were lower; NDE was higher than these of Hexaploid. Variation of NPE andNYE was higher than other NUE indexes, which indicated that NPE and NYE could beused as indexes for NUE differences in different wheat related species. The correlationanalysis showed that nitrogen accumulation was base of grain yield, nitrogen transfer andnitrogen accumulation when under control. But the more N accumulation limited grainyield, NTE, NHI and NPE to increase as it need more energy and organically matter whenunder nitrogen treatment. NHI, NYE and NPE were significantly positively correlated.2. The differences of nitrogen metabolism and its relationships with nitrogenutilization efficiency were investigated. The results showed that N uptake of diploid andtetraptoid were lower than those of Hexaptoid and octoploid at over wintering and afteranthesis, but the capability was higher from jointing to anthesis. Diploid and tetraploid hadlower N distribution in leaf, and had higher N distribution in else vegetative parts at anthesis. And had lower N distribution in grain, higher N distribution in else vegetativeparts at mature. The N transfer amounts and its contribution to grain N accumulation ofDiploid and tetraploid were higher than Hexaploid, but the NTE and contribution of Naccumulation to grain N were lower. The correlation analysis showed that the NDEincreased with the increasing of N metabolism Enzymes at booting and anthesis. The NYE,NHI and NPE increased with the increasing of N metabolism Enzymes during late fillingperiod.3. The differences of carbon metabolism characteristics and its relationships withnitrogen utilization efficiency were investigated. The results showed that the diploid andtetraploid had higher capability of dry matter accumulation from jointing to anthesis, andhad less dry matter accumulation at over wintering and after anthesis compared withHexaploid. Contribution of dry matter transfer to grain yield was higher, contribution of drymatter accumulation was lower than that of Hexaploid after anthesis. Thephotosynthetic rate (P_n) of diploid and tetraploid are higher than that of Hexaploid beforeanthesis. The reason for this phenomenon was that diploid and tetraploid had higherstomatal conductance (g_s), maximum photochemical efficiency (F_v/F_m) and actual lighttransformation efficiency (φ_PSâ…¡. However, the Pn of diploid and tetraploid declined morequickly and became much lower than those of hexaploid species from 5 days after anthesisexcept S.cereale. Moreover, Fv/Fm,φ_PSâ…¡ and chlorophyll content of diploid and tetraploiddeclined more quickly, while intercellular CO₂ concentration(C_i) increased, which resultedin non-stomatal inhibition to P_n. Furthermore, the leaf area per plant of hexaploid andoctoploid species declined more slowly after anthesis as compared with diploid andtetraploid species though diploid and tetraploid had higher leaf area before anthesis. Soimproved photosynthetic capacity and duration after anthesis were important physiologicalbasis for grain yield, NYE, NHI and NPE enhancement.4. The differences of root activity, flag leaf soluble protein content, MDA content,SOD and CAT activity and its relationships with carbon and nitrogen metabolism wereinvestigated. The results showed that diploid and tetraploid had higher root activity, flagleaf soluble protein content, SOD and CAT activity before anthesis. However, the rootactivity, flag leaf soluble protein content, SOD and CAT activity of diploid and tetraploiddeclined more quickly and became lower than those of hexaploid species from 15 days afteranthesis. While MDA content increased more quickly and became higher than those ofhexaploid species from 5 days after anthesis. Correlation analysis showed that delaying the flag leaf senescence can promoted transfer of nitrogen and dry matter, increasedaccumulation of nitrogen and dry matter after anthesis, enhanced grain and protein yield. Sodelayed root and flag leaf senescence after anthesis was important physiological basis forenhancement of grain yield, carbon and nitrogen metabolism.5. The differences of root morphology, root activity and N metabolism enzymes and itsrelationship with N uptake at seeding stage. The results showed that the Triticale andS.cereale and tetraploid species had longer length, bigger surface area and volume, higherfresh weight and total root activity and NR activity of root and leaf, higher N uptake.Correlation analysis showed that the N accumulation was significantly positively correlatedwith root length, surface area, volume and physiological activity. So it is very important forN uptake and accumulation to increase wheat root length, surface area, volume andphysiological activity.