Meng Yali

Effect of Nitrogen Rates and Flowering Dates on Fiber Quality of Cotton (Gossypium hirsutum L.)

Nitrogen (N) supply during boll setting and maturation period of cotton can be critical in determining fiber quality. The study aims to investigate the relationship between N rates and formation of fiber length, strength, maturity and micronaire in bolls with different flowering dates. Field experiments were conducted using two cotton cultivars (Kemian 1 and NuCOTN 33B) and three N fertilization rates (0, 240, and 480 kg N ha -1 ) in Nanjing and Xuzhou in 2005 and in Anyang in 2007, China. The fiber length, strength, maturity, micronaire, and N concentration per unit area (N A) of the subtending leaf of cotton boll were analyzed. N fertilization rates, flowering dates, and N fertilization rates × flowering dates significantly (P ≤ 0.05) affected N A and the formation of fiber length, strength, maturity and micronaire. N fertilization rates affected fiber quality by influencing NA which was significantly related to rate and duration of the fiber quality formation process. The optimal N A for fiber quality formation was varied. For bolls flowering before August 25, when mean daily temperature during boll maturation period (MDT BMP ) was higher than 21°C, NA in the 240 kg N ha -1

Effect of Planting Date and Boll Position on Fiber Strength of Cotton (Gossypium hirsutum L.)

The effect of planting date and boll position on cell wall thickening of cotton fiber and development of fiber strength were studied by comparing the time course of the activity of key enzymes β-1,3-glucan synthase (callose) and sucrose synthase (SuSy) involved in cellulose biosynthesis, cellulose content and the indices of fiber structure X-ray diffraction of the fiber that developed at different planting dates or boll positions. The results showed that during the fiber cell wall thickening and fiber strength formation stage (25-50 days post-anthesis, DPA), there was an interactive effect between planting date and boll position. Different planting dates resulted in different mean daily temperatures during 2550 DPA (T DPA 25-50 ), which was always an important factor that influenced fiber strength, while the impact of boll position in different temperature conditions was variable. When TDPA 25-50 was above 22.0°C, boll position might affect the cell wall thickening process and the fiber strength, while when T DPA25-50 was lower than 20.0°c, boll position affect little. The optimum conditions for the development of fiber cell wall thickening and the formation of fiber strength may be the eighth nodal position of the fruiting branch (PFB) and with the TDPA 25 -50 of about 26.0°C. Research Article