| The population physiological characteristics of both small spike-type cultivar (yumai 49) and large spike-type cultivar (yumai 66) were studied under field conditions, and the regulating effects of nitrogen and irrigation management were investigated as well. The main results are as follows:1. Irrigation frequency and nitrogen rate had a direct effect on the development of assimilating organ area and the same trend in the changes of population was observed in both cultivars. With the increasing of irrigation frequency and nitrogen rate , the LAI increased during wheat development because of slower senescence. Meanwhile, ears per unit area increased. There were differences between two cultivars in population development. Although yumai 66 had fewer culms per unit area after booting stage, it could maintain higher LAI during grain filling because of better light condition in canopy and slower senescing of leaves.2. Irrigation frequency and nitrogen rate regulated N, P and K content in two winter wheat cultivars. N, P and K content in leaves increased when nitrogen rate raised. Water and nitrogen had different regulating effects. Water stimulated transportation of N and P. N content in leaves enhanced with increasing of irrigation frequency from anthesis to mature, but P content in leaves of W2 was lowest at filling stage and declined with increasing of irrigation frequency at maturity. Effect of water on K content in leaves was not stable, as for yumai 66, K content of W2 was highest from filling to harvest, as to yumai 49 , that of Ws was highest from anthesis to harvest.3. There was distinct difference between two cultivars in C-N metabolic characteristics and grain development during grain filling stage and both cultivars were affected by water and nitrogen. Nitrate reductase (NR) activity and soluble protein content in flag leaf increased when irrigation frequency and nitrogen rateenhanced, which showed that N metabolic activity was strengthened. Changes of the WSC content of limited water supply (W2) was stable in flag leaf, which suggested that W2 had stronger source supplying ablility persistently. The WSC content of limited nitrogen supply (N2) was lower in flag leaf. It revealed that N2 maintained stronger flow activity and rapid translocation of assimilating matter, which stimulated grain to fill. The WSC content in grain declined when irrigation frequency increased in the late grain-filling stages, which promoted WSC to become starch. During the initial and mid grain-filling stage, the treatment of suitably higher nitrogen raised the WSC content in grain, which indicated that supplying ability of assimilate was enhanced , and therefore kernel-weight could increase rapidly. There was significant positive correlation between grain filling rate and starch accumulating, both were lower in the initial grain-filling stage and higher in the late grain-filling stage when irrigation frequency and nitrogen rate increased. NR activity and soluble protein content in flag leaf of yumai 66 were higher than that of yumai 49, which showed that its leaves senesced slowely. During the grain-filling peak, the WSC content in leaves and grain was higher, which showed that the massive -spike cultivar had stronger source supplying ability.4. Irrigation and nitrogen management affected ch1, Fv/Fo, Fv/Fm, qP, qN, psIIand Pn of flag leaf in two wheat varieties with different spike types to some content. Chlorophyll contents increased when more nitrogen was applied. Chi contents of N3 treatment was little higher than that of N2 treatment, but Ch1 contents might be decreased by too much nitrogen. Irrigation can let leaf senesce slowely and enhanced Chi contents especially in the late growth period. ChK car, chla/chlb, chl/car of flag leaf in Yumai 66 were higher than in Yumai 49 in the late filling stage, which could alleviate the degradation of chl, stimulate increasing of photosynthesis. PSII activity (Fv/Fo) and the maximal quantum efficiency o... |
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