Effects Of Nitrogen Application On Source-Sink Trait Of High Starch Maize (Zea Mays L.)

The high starch maize is referred to the seed starch content to reach over 74ï¼…for special purpose, but the ordinary maize only about 65ï¼…. The maize starch production industry holds the important proportion in the entire maize processing industry. Yield and the quality formation of the high starch maize is closely related to dry matter accumulation, the nutrient uptake, carbon and nitrogen metabolism, and the grain sugar and starch formation. Nowadays, researches are mainly focused on the source and sink dynamics influenced by nutrients in ordinary maize, while regarding recent developed high starch maize, the research is obviously insufficient and not systematic. In this paper, field experiment, plant analysis and scanning electron microscope observation were used to investigate the effects of nitrogen application on dry matter accumulation, nutrient uptake, carbon and nitrogen translocation, and sugar and starch formation in high starch maize of Jidan 535, as compared with the ordinary maize of Jundan 8, so as to provide theory basis for rational fertilization of high starch maize. The main findings are summarized as follows:1. The dynamic changes of total biomass and grain weight in maize could be described by Logistic equation, and that of vegetative mass by exponential equation as Y=axe^bx; Biomass yield (Y) was a function of grain yield (x₁) and vegetative mass (x₂), as described by regression equation of Y=exp(a+b₁x₁+b₂x₂). As compared with Jundan 8, the ordinary maize, dry weight of vegetative in high starch maize of Jidan 535 increased with a longer duration, and then decreased with a lower rate, thus the translocation amount of dry matter from vegetative mass to grain is found to be lower. The appropriate N application rate and the ratio of basal to dressing is beneficial to biomass accumulation in vegetative growth stage and dry matter translocation from the vegetative to the grain, therefore higher grain yield was obtained in high starch maize. The proper application rate of nitrogen fertilizer is 200 kg N/ha for high starch maize of Jidan 535, and the ratio of basal to dressing is 1:2.2. The accumulation process of nitrogen (N), phosphorous (P) and potassium (K) in maize could be described by Logistic equation. The highest nutrients absorption rate (HAR) was obviously influenced by N application rate. The appropriate N application rate and the ratio of basal to dressing resulted in high HAR, and the occurring date of HAR came earlier for K absorption. Higher starch maize received lower HAR for N and P under the appropriate N application rate than ordinary maize. The HAR of N and P occurred in mid-later growth stage, later than K, suggesting that a spit application is needed to improved N utilization efficiency. In regarding to the characteristics that P is immovable and K is soluble in the soil, therefore suggesting P and K should be applied as basal fertilizer. At appropriate N application rate, the amount of N, P and K required for the production of 100 kg grain for high starch maize, was 2.059 kg N, 0.544 kg P₂O₅, and 1.345 kg K₂O, with the corresponding ratio of 1:0.26:0.65.3. As compared with Jundan 8, the dry matter transloation from vegetative during grain filling and maturity was lower in Jidan 535, and the carbon in grain mainly relied on the current photosynthate. 82.4ï¼…of carbon in grain in Jidan 535 comes from current photosynthate, and 17.6ï¼…from translocation from vegetative part, while that was 74.8ï¼…from photosynthate, and 25.2ï¼…from translocation from vegetative part for Jundan 8 under the appropriate N application rate. For indan 535, N in grain from root N uptake and from vegetative N translocation was 31.1ï¼…and 68.9ï¼…respectively, and that for Jundan 8 was 36.3ï¼…and 63.7ï¼…respectively under appropriate N application rate.4. For two maize cultivars, starch concentration in grain increased with the N applied when N application rate was from 0 to 200 kg N/hm², and the value reduced when N was over 200 kg N/hm². The concentration of sucrose, fructose and glucose in Jidan 535 was higher than Jundan 8 at grain filling, higher concentration of sucrose, fructose and glucose acquired under appropriate N application. Starch granule in the grain of Jidan 535 was full of cell uniformly, and starch granules in the grain of Jundan 8 were arranged in a confusion form. Appropriate N application led starch granule arranged uniformly, but those were squeezed to the status of polyhedron with excessive N application.