A novel cottong ovule culture: Induction, growth, and characterization of submerged cotton fibers (Gossypium hirsutum L.)

Abstract

The growth of submerged cotton (Gossypium hirsutum L.) fibers from cultured ovules has been investigated. The results indicate that exogenous plant hormone levels regulate the induction of submerged fiber growth. The age of ovules at induction is also important. Cell diameter, wall thickness, and cell length of submerged fibers were measured and compared with air-grown fibers and fibers grown in vivo (produced by cotton plants grown in the greenhouse). Various cellwall thickening patterns were observed among submerged fibers, while only one predominant cell-wall deposition pattern was produced in air-grown fibers and in fibers produced in vivo. The diameter of submerged fibers was about the same as that of air-grown fibers but about 22% less than that of fibers grown, in vivo. It appears that the secondary cell wall thickenings are initiated earlier in submerged fibers. The cell-wall thickness of submerged fibers, at 41 d post anthesis (DPA), was 51% greater than that of fibers grown in vivo, whereas the cell-wall thickness of air-grown fibers was 42% less than that of fibers produced in vivo. The cell length of submerged fibers was approximately half that of fibers grown in vivo. and the air-grown fiber length was about two-thirds of fibers grown in vivo. The age of ovules at induction affects the outcome of the air-grown fiber-cell length, but does not appear to affect the length of submerged fiber cells. To produce submerged fiber growth, we found that the optimal age of ovules at induction was 0 DPA, and the optimal medium (with a GA3 of 0.5 μM and an IAA range of 5-20 μM) depends on the time of ovule induction (−2 to+2DPA). We conclude that conditions leading to submerged cotton fiber growth have great potential for (a) direct monitoring of growth and making precise, detailed measurements during fiber growth and development; (b) producing cellulose and fibers in vitro more efficiently than earlier ovule-culture methods; and (c) using these unique cultures to obtain a better understanding of signal transduction and gene expression leading to growth, development, and programmed cell death in the life history of the cotton fiber.