| Cottonseed and fiber are important raw materials in industry or in agriculture, the quality of the both determines the quality of their cotton bolls. Nitrogen is one of the regulating factors to the quality of cotton boll. Nowadays, improper applying nitrogen fertilization significantly depressed the quality of cotton bolls. For improving the quality of cotton boll by regulating nitrogen fertilizer application, the effection of characteristic of nitrogen accumulation and distribution in cotton bolls bloomed at different date on the quality formation of cotton bolls was studied in this research to provide theoretical basis. One cotton cultivar (NuCOTN 33B) was used, with three nitrogen application rates (NO:0 kg N ha-1, N240:240 kg N ha-1, N480:480 kg N ha-1) in field experiments in Xuzhou (117°11'E, 34°15'N, Yellow River Valley), Jiangsu province, and Anyang (114°13'E,36°04'N, Yellow River Valley), Henan province, to investigate the characteristic of nitrogen accumulation and distribution in cotton bolls bloomed at different dates (July15, August10, August25, and September10, expressed as PSB, SB, EAB and LAB, respectively) and its response to nitrogen concentration in the subtending leaf of cotton boll, and relationship between characteristic of nitrogen accumulation and distribution in cotton bolls bloomed at different dates and cotton boll quality formation.1. Characteristic of nitrogen accumulation and distribution in cotton bolls bloomed at different dates and its response to nitrogen concentration in the subtending leaf of cotton bollThe results showed that the accumulation of nitrogen in cotton bolls under different blooming stage could be simulated with Logistic equation. The ratio of nitrogen distribution of cotton boll could be simulated with quadratic:Y=at2+bt+c (Y stands for the ratio of nitrogen distribution of cotton boll(%), t stands for boll age (d)). Correlation analysis indicated:(1) The nitrogen accumulation in cotton boll-shell, cottonseed, cotton fiber and single boll were significantly affected by the nitrogen rates of supply at the two experimental sites. Firstly, discussing on the same seasonal cotton boll with different nitrogen rates, the theoretic maximum of nitrogen accumulation in cotton boll of N240 treatment was the highest, and was lower in cotton boll of N480 treatment and was the lowest in cotton boll of NO treatment. Secondly, discussing on the cotton bolls in different blooming stages with the same nitrogen rate, the theoretic maximum nitrogen accumulation in cotton boll of SB and PSB was the highest, and was lower in cotton boll of EAB and was the lowest in cotton boll of LAB. (2) The nitrogen distribution in cotton boll-shell, cottonseed and cotton fiber was significantly affected by the nitrogen rates of supplication and blooming stage at the two experimental sites. Firstly, discussing on the same seasonal cotton boll with different nitrogen rates, the theoretic maximum of nitrogen distribution in boll shell of N240 treatment was the lowest, and was higher in cotton boll of N480 treatment and was the highest in cotton boll of NO treatment, however the theoretic maximum of nitrogen distribution in cottonseed and cotton fiber was otherwise. Secondly, discussing on the cotton bolls in different blooming stages with the same nitrogen rate, the theoretic maximum nitrogen distribution in cotton boll shell of SB and PSB was the lowest, and was higher in cotton boll of EAB and was the highest in cotton boll of LAB, however the theoretic maximum of nitrogen distribution in cottonseed and cotton fiber of SB and PSB was the highest, and was lower in cotton boll of EAB and was lowest the in cotton boll of LAB. (3) The response of characteristic of nitrogen accumulation and distribution in cotton bolls bloomed at different dates to nitrogen concentration in the subtending leaf of cotton boll proved that the nitrogen accumulation and distribution in cotton bolls bloomed at different dates was correlative with nitrogen concentration in the subtending leaf of cotton boll. The nitrogen accumulation in cotton bolls bloomed at different dates was higher when the nitrogen concentration in the subtending leaf of cotton boll was moderate, but it would be decreased when the nitrogen concentration in the subtending leaf of cotton boll was too lower or too higher. When the nitrogen concentration in the subtending leaf of cotton boll was higher at the flowering day, and the nitrogen concentration in the subtending leaf of cotton boll decreased slower as boll age was bigger, the theoretic maximum of nitrogen distribution in cotton fiber would be increased, and nitrogen was inclined to transport to cotton fiber.2. Effects of characteristic of nitrogen Accumulation and Distribution of Cotton Boll under Different Blooming Stage on Characteristic of Cottonseed Protein and Fat AccumulationThe accumulation of protein and fat in cottonseed under different blooming stage could be simulated with Logistic equation. The dynamic eigenvalues of cottonseed protein and fat accumulation was significantly affected by nitrogen rates, also was different under different blooming stage at the two experimental sites. The dynamic eigenvalues of cottonseed protein and fat accumulation with the nitrogen rates of N240 treatment were more harmonious than that with other treatments. The theoretic maximum protein and fat accumulation in cottonseed of SB and PSB was the highest, and was lower in cottonseed of EAB and was the lowest in cottonseed of LAB. The effect of characteristic of nitrogen accumulation and distribution in cotton bolls bloomed at different dates under different nitrogen rates on cottonseed protein and fat accumulation proved that the average rate of protein accumulation during the speedy accumulation period was faster, and the date of reaching the minimum of the boll-shell nitrogen distribution ratio was later and the minimum of the boll-shell nitrogen distribution ratio was lower, and the date of reaching the maximum of the cottonseed or cotton fiber nitrogen distribution ratio was earlier, and the maximum of the cottonseed nitrogen distribution ratio was higher, then nitrogen would be clinced to be transported to cottonseed, then the of accumulation cottonseed protein was promoted, but the accumulation of cottonseed fat was retarded.3. Effections of Characteristic of Nitrogen Accumulation and Distribution of Cotton Bolls Bloomed at Different Dates on Cotton Fiber Main Quality Characteristics formationCompared with N240 treatment, the cellulose speedily accumulating duration in cotton fiber and the fiber strength of SB and AB were decreased obviously under NO and N480 treatment. The effect degree under NO treatment increased with blooming date postponing, and the decline of the duration for cellulose speedily accumulating lead to the decrease of fiber strength, however N480 treatment did otherwise, fiber length did similiar trend. Micronaire was improved under NO treatment, but was depressed under N480 treatment. Nitrogen accumulation and distribution in cotton bolls bloomed at different dates was correlative with cotton fiber quality characteristics formation. When the average rate of nitrogen accumulation during the speedy accumulation period was faster, the date of reaching the maximum of the cotton boll shell nitrogen distribution ratio was later, the minimum of the boll shell nitrogen distribution ratio was lower, and the date of reaching the maximum of the cottonseed nitrogen distribution ratio was earlier, and the maximum of the cottonseed nitrogen distribution ratio was higher, then improved the average rate of nitrogen accumulation during the speedy accumulation period, and micronaire was optimized, however the duration for nitrogen speedy accumulation period in cotton bolls was shortened, and fiber strength and length was not improved.In conclusion, the accumulation of nitrogen in cotton bolls under different blooming stage could be simulated with Logistic equation. The ratio of nitrogen distribution of cotton boll could be simulated with quadratic:Y=at2+bt+c (Y stands for the ratio of nitrogen distribution of cotton boll(%), t stands for boll age (d)). The nitrogen accumulation and distribution in cotton bolls bloomed at different dates was correlative with nitrogen concentration in the subtending leaf of cotton boll. The nitrogen accumulation and distribution in cotton bolls bloomed at different dates effected on the protein and fat accumulation in cottonseed and the quality formation of cotton fiber. |
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