Study On Growth, Physiology Characteristics Of Colored Cotton Cultivars And The Regulation

The study was undertaken on nature-colored cotton cultivars, which were Wuan mian No.39 (green cotton cultivar) and Xiang cai No.2 (brown cotton cultivar) during 2006 and 2007 growing seasons at the Jiangsu Provincial Key Laboratory of Crops Genetic and physiology, Yangzhou University, Yangzhou, China. In the study, Wuan mian No.39, Xiang cai No.2 and Su mian No.9 were grown to investigate the characteristics of development, the carbon and nitrogen metabolism, and to research the adjustable approach and physiological mechanism of improving fiber quality and pigment in colored cotton fiber. The main results were as follows:1. The characteristics of development changed. In the aspect of vegetative growth, the colored cotton had bigger growth rate for plant height and LAI than Su mian No.9. For example, the speed of plant height growth for green cotton, brown cotton cultivar and the control were 1.50 cm/d, 1.38 cm/d and 1.06 cm/d respectively. At the peak boll period, LAI were 5.14, 4.3 and 4.12 for Xiang cai No.2, Wuan mian No.39 and Su mian No.9 respectively. In the aspect of reproductive growth, the colored cotton had more fruit-nodes (3.26, 3.31 millions·hm-2 for green and grown cotton) than the control (3.23 millions·hm-2). However, the green and grown cotton had higher shedding rate of buds and bolls, and fewer bolls per plant, and lower intensity of boll setting, and lower vegetative dry matter weight, the ratio of reproductive organs and vegetative organs dry matter weight. The boll development characteristics were different between colored cotton and white cotton. In comparison with the control (Su mina No.9), the boll length, the boll diameter, the boll volume, the boll husk weight and the boll weight were lower for colored cotton. For example, the boll volume of green and brown cotton was only 75.4%, 85.3% of the white cotton's.2. Colored cotton had weak carbon physiological metabolism, but strong nitrogen physiological metabolism at later growing stage. The colored cotton had weaker NR activity, GPT activity, and the content of amino acid, total nitrogen and the soluble protein in functional leaf before peak flower period. However, they had stronger nitrogen physiological metabolism than the white cotton at later growing stage. For example, the content of total nitrogen in functional leaf enhanced by 7.2%, 10.3% for green and brown cotton respectively in comparison with Su mina No.9 at boll open stage. In whole growing stage, the colored cotton had lower content of chlorophyll, soluble sugar, weaker net photosynthetic intensity, and lower activity of invertase in functional leaf. Compared with the control, the C/N (the content of soluble sugar/ the content of total nitrogen) in functional leaf was lower for the colored cotton.3. The speed of fiber quality development and physiological activities of fiber cell for the colored cotton were lower than those of the white cotton. The fiber length, the fiber strength, the fiber micronair, and the fiber maturity of Xiang cai No.2 were 95.5%,88.4%,89.2%,95.9%of Su mian No.9's. Dynamic formation of the fiber quality indicated that the development speed of the fiber length for Xiang cai No.2 and Wuan mian No.39 were 0.89 mm/d and 0.85 mm/d which were lower than 0.98 mm/d of Su mian No.9. The lower fiber micronair and the fiber maturity for the colored cotton were due to the slower accession during 0 to 30 days post anthesis (DPA). The parameters of the Richards equation indicated that the beginning parameter (b) and accumulative rate parameter (K) of the fiber length, the fiber micronair, and the fiber maturity for the colored cotton were lower than those of the white cotton. The results of the physiological activities of fiber cell were as followed: The leaf chlorophyll content, the fiber and boll husk ATPase activities, the fiber Sucroase Synthase (SS) activities, the fiber UDPG-Pyrophosphorylase (UDPP) activities for colored cotton were lower than those of the white cotton. For example, the fiber ATPase activity for Wuan mian No. 39 was 42.2% of that of Su mian No.9.4. In comparison to Xiang cai No.2, equilibrium between vegetative and reproductive growth for Wuan mian No.39 was worse, neither the coordination carbon and nitrogen metabolism. After flower period, the content of total nitrogen, soluble protein and the GPT activity for Wuan mian No.39 were lower than those for Xiang cai No.2. For example, the content of total nitrogen reduced by 4.1 percentage for Wuan mian No.39 in comparison to Xiang cai No.2 at peak flower period. The contents of chlorophyll, soluble sugar, and net photosynthetic intensity for Wuan mian No.39 were lower than those for Xiang cai No.2. Compared with Xiang cai No.2, the content of soluble sugar reduced by 14.1% for Wuan mian No.39. The C/N for Wuan mian No.39 at the early flowering period (8.03), the peak flower period (13.45), the boll opening period (15.30) were lower than those for Xiang cai No.2, which were 12.42, 15.02, 18.21.5. The pigment in the fiber of Xiang cai No.2 was higher than that of Wuan mian No.39. It had great concern with the ABA, GA₃ content and other relevant enzymes activities. The results showed that the pigment content (estimated by absorbance reading at 412 nm for distillation solution in 0.1g fiber) for Xiang cai No.2 was 0.418, for Wuan mian No.39 was 0.385. And the pigment of green cotton was unstable and of photo-degradation. For example, the absorbance reading of pigment in green and grown cotton fiber reduced by 0.221, 0.113 after 5 hours under the sunlight. The brown cotton had more content of fiber ABA and GA₃ at 40 DPA than green cotton. And there were significant positive correlation between the pigment content and the content of ABA, GA₃ (r=0.6668*, r=0.7993**). The content of fiber tannin and the Phenylalanine Ammonia-lyase (PAL) activity for green cotton were lower than those for brown cotton. For example, the PAL activity for green cotton reduced by 30.8 Unit·g^-1·fw^-1·h^-1 in comparison with brown cotton. And the PAL activity was uniformity to the pigment content.6. With the density of 37500 plants/hm² and the fertilizer of N of 225 kg/hm², the brown cotton maintained the population at reasonable range and the yield, the fiber quality enhanced. That density and fertilizer level adjusted the development of plant height and LAI. The final plant height was 100.3 cm. The maximum LAI was 4.17. In the aspect of reproductive growth, dry matter accumulation of individual plants, the number of bolls, the intensity of boll setting, the boll weight and the pint enhanced under that density and the fertilizer. The shedding rate of buds and bolls reduced. For example, the shedding rate of buds and bolls reduced by 29.8%, 23.0% respectively in comparison to the density of 37500 plants/hm², the fertilizer of N of 225 kg/hm² and the density of 37500 plants/hm², the fertilizer of N of 0 kg/hm²; the yield increased by 24.6%, 1.8% respectively.7. Three kinds of growth regulators (DPC, DTA-6, GA₃) could adjust the carbon and nitrogen physiological metabolism, improve the development of bolls, enhance the physiological activities, improve the fiber quality. The DTA-6, GA₃ enhanced the boll volume and weight. For example, the treatment of GA₃ sprayed increased the boll volume by 4.9 cm3 and 3.5 cm3 respectively for green and grown cotton. The treatment of GA₃ sprayed enhanced the boll weight by 0.78g for green cotton. The treatment of DTA-6 sprayed increased the boll weight by 0.58g for brown cotton. DPC, DTA-6, GA₃ enhanced the fiber length, the fiber strength, the fiber micronair, and the fiber maturity of colored cotton and decreased the difference at different positions. The treatment of GA₃ sprayed enhanced the fiber length, the fiber strength, the fiber micronair, and the fiber maturity by 2.2, 26.7, 5.0, 8.1 percentage points respectively for green cotton, and 6.0, 5.5, 13.9, 9.4 percentage points respectively for grown cotton. Treatments of three kinds of growth regulators sprayed enhanced the leaf chlorophyll content, the fiber invertase activities, the fiber ATPase activities, the fiber Sucroase Synthase (SS) activities, the fiber UDPG-Pyrophosphorylase (UDPP) activities and the endogenous hormones content. Take the ATPase activities for example, the treatment of DPC, DTA-6, GA₃ sprayed enhanced by 3.10 umol·gfw^-1·h^-1,3.96 umol·gfw^-1·h^-1,6.34 umol·gfw^-1·h^-1 respectively for green cotton in comparison with the control.DPC, DTA-6, GA₃ could adjust the intensity of the carbon and nitrogen physiological metabolism and the coordination between them. Firstly, DPC, DTA-6, GA₃ enhanced the nitrogen physiological metabolism at early growing stage, but DPC decreased it at late growing stage. Secondly, DPC, DTA-6, GA₃ enhanced the carbon physiological metabolism at peak bolling and the boll opening stage. Treatments of DPC, DTA-6, GA₃ sprayed enhanced the soluble sugar content by 6.0%, 20.5%, 14.0% respectively for green cotton and by 12.5%, 8.0%, 28.5% respectively for brown cotton at peak bolling stage. Thirdly, DPC, DTA-6, GA₃ adjusted the C/N at peak bolling and the boll opening stage, improved the development of reproductive organs at late growing stage. At the boll opening stage, the treatments of DPC, DTA-6, GA₃ sprayed improved the C/N by 53.3, 46.0, 49.5 percentage points respectively for green cotton and by 9.8, 5.3, 7.2 percentage points respectively for brown cotton, especially DPC, GA₃ got the better effect.8. Cutting off appropriate buds treatment improved the boll development, enhanced the fiber quality and the physiological activities for colored cotton. The treatments of cutting of the half and quarter of whole buds in plant enhanced the boll weight by 1.346g and 1.051g respectively for green cotton, by 0.622g, 0.313g respectively for brown cotton. The treatment of cutting off buds improved the fiber length, the fiber strength, the fiber micronair, and the fiber maturity, especially for green cotton. The treatment of cutting off half of whole buds in plant enhance the fiber length, the fiber strength, the fiber micronair, and the fiber maturity by 14.9, 11.0, 18.7, and 16.2 percentage points respectively for green cotton, by 8.6, 6.5, 11.4, 11.8 percentage points respectively for brown cotton. The treatment of cutting off buds increased the leaf chlorophyll content, the fiber invertase activities, the fiber ATPase activities, the fiber Sucroase Synthase (SS) activities, the fiber UDPG-Pyrophosphorylase (UDPP) activities and the endogenous hormones content. For example, the treatments of cutting of half and quarter of whole buds in plant increased the fiber SS activities by 36.6% and 15.1% respectively for green cotton, by 76.1% and 56.7% respectively for brown cotton.9. DPC, DTA-6, GA₃, cutting off buds and the slight shading treatment increased the content of pigment and tannin, the PAL activities in fiber. The treatment of GA₃ sprayed enhance the pigment content in fiber by 23.9 and 6.5 percentage points for green and brown cotton respectively. The cutting off the half of whole buds in plant treatment increased the pigment content by 54.3 and 9.8 percentage points for green and brown cotton respectively. The slight shading treatment enhanced the pigment content by 9.5 and 3.6 percentage points for green and brown cotton respectively.10. The treatment of Fecl3 sprayed improved the stability of the pigment in two colored cotton varieties fiber. Firstly, Fecl3 sprayed treatment enhanced the pigment content in fiber by 4.4% and 3.6% respectively for green and brown cotton. Secondly, the treatment of Fecl3 sprayed reduced the decomposing of the pigment in colored cotton fiber. After 5 hours under the sunlight, the absorbance reading of pigment in fiber decreased only 0.061 and 0.062 respectively for green and brown cotton.