Abstract:

Cotton is a fine natural fiber, an important textile, and a major industrial resource, accounting for nearly half of the world’s natural fiber consumption. Understanding the growth and development of cotton fibers is thus of global importance. Cotton fiber development is divided into four overlapping stages: fiber initiation, fiber elongation, secondary wall thickening, and maturation. The development of fiber initiation might include these aspects such as fiber cells differentiation, fiber protrusion, and initial elongation. At present, many studies on cotton fiber differentiation and development have been documented, but most of them are focused on Gossypium hirsutum, and the reports of comparative studies on fiber development among cotton species are ever less. Here we observed the ovules before and after anthesis of four cultivated cotton species including Gossypium hirsutum cv. Simian 3, Gossypium barbadense cv. Hai 7124, Gossypium arboreum cv. Dingyuan xiaohua, and Gossypium herbaceum cv. A1-50 by utilizing SEM (scanning electron microscope), and explored the influence of delay pollination on fiber initiation development of each cultivar. The results showed that under the climate conditions in the field at Nanjing, fiber cells protruded on the ovular surface in all cultivars except G. arboreum at 1 day before anthesis. At 0 and 1 day post-anthesis (DPA), fiber protrusion (or elongation) density of all materials was the highest at the funicular crest, higher at the chalazal cap and the middle part of ovule, and the least near the micropyle; moreover except upland cotton cultivar Simian 3, fiber density of the other three cultivars was lower at 1 DPA than that at 0 DPA, suggesting that with the expanding of the cotton ovular volume , the fiber "diluting" degree on the ovular surfaces was greater in G. barbadense, G. arboreum and G. herbaceum than in G. hirsutum. During cotton fiber initial stage, fiber density not only was affected by weather factors such as temperature but also related to the viability of stigma. Delay pollination exerted relatively significant influence on fiber initiation development of G. herbaceum, relatively less influence on G. barbadense, and the least influence on G. hirsutum and G. arboreum. Our studies might provide some theoretical references on understanding the mechanism of cotton fiber differentiation and growth, and exploring the phylogenetic relationships of fiber development of four cultivated cottons, as well as utilizing the heterosis of cotton fiber through artificial pollination.

Key words: Cultivated cotton species, Fiber initiation development, Fiber density, SEM (scanning electron microscope), Delay pollination