Abstract: 【Objective】 In order to establish and optimize theovule culture system of brown cotton and green cotton, the effects of growth substances (osmotic regulators, plant growth regulators and flavonoids biosynthesis precursors) on the fiber growth and development were studied.【Method】Brown cotton variety Z1-61, green cotton variety CC28 and the white cotton variety RT-White (control sample) were used as plant materials. The conventional ways of cultivation and management were adopted. Flowers were tagged at 0 day post anthesis (DPA), and then the ovules of 3 DPA were used for ovule culture in vitro. Besides the addition of 10.0 μmol·L^-1 IAA and 5.0 μmol·L^-1 GA3, different concentrations of osmotic regulators (mannitol, NaCl, KCl and sucrose), plant growth regulators (MeJA and BR) and flavonoids biosynthesis precursors (phenylalanine and ferelic acid ) were added to the basic BT medium, respectively. Except investigating the interaction effect between brassinolide and methyl jasmonate, the other experiments were chosen variety and treatment for dual factors test. After being cultured in vitro for 30 days, the fiber color, fiber length, ovule fresh weight, ovule dry weight and fiber dry weight of Z1-61, RT-White, and CC28 were determined. The mean value and standard error were calculated and multiple comparisons were carried out using least significant difference(LSD) or shortest significant ranges(SSR).【Result】Color cotton pigmentation was observed until 15 d after ovule culture in vitro. The best treatment for color cotton ovule growth and fiber development was 5 g·L^-1 sucrose, under which the fiber length, ovule fresh weight, fiber dry weight and ovule dry weight of Z1-61 was significantly increased by 28.35%, 20.69%, 103.70% and 75.84% (P＜0.05), while that of CC28 was significantly increased by 8.10%, 16.07%, 63.14% and 82.76% (P＜0.05), respectively, compared with the controls. In 0.05 μmol·L^-1MeJA treatment, the fiber length of Z1-61 was significantly increased by 22.90% (P＜0.05), while that of CC28 was increased by 4.39%. In 0.5 μmol·L^-1 BR treatment, the fiber length of Z1-61 and CC28 was significantly increased by 22.46% and 11.56% (P＜0.05), respectively. In 25 μmol·L^-1 ferelic acid treatment, the fiber length of Z1-61 and CC28 was significantly increased by 8.72% and 8.81%（P＜0.05), respectively. Furthermore, 30 g·L^-1 mannitol, 0.1 mol·L^-1 NaCl, 0.20 mol·L^-1 KCl, 10 g·L^-1 sucrose, 40 μmol·L^-1 methyl jasmonate or 0.10 mmol·L^-1 phenylalanine were conducive to the pigment accumulation of brown cotton fiber. Among them the best treatment was 40 μmol·L^-1 MeJA. However, the growth substances used in this experiment did not cause any significant change in the pigment appearance of green cotton.【Conclusion】Sucrose provided the sugar source and osmotic environment for color cotton ovule growth and fiber development, and the appropriate concentrations of MeJA, BR or ferulic acid benefited the fiber elongation. There was a cross-effect between BR and MeJA. BR was mainly involved in fiber elongation, while MeJA may be involved in the pigment accumulation of brown cotton. Furthermore, certain concentrations of mannitol, NaCl, KCl, sucrose, MeJA or phenylalanine were advantageous to the brown cotton fiber pigment synthesis. However, neither osmotic regulators, plant growth regulators nor flavonoids biosynthesis precursors caused any significant change to the pigment accumulation of green cotton.

Key words: color cotton, fiber growth, pigment synthesis, osmotic regulators, plant growth regulators, precursors