Cotton fiber length is affected by far-red light impinging on developing bolls

Cotton (Gossypium hirsutum L.) fiber length Is an important component of qu ality as defined by the textile Industry. The fibers are single elongated c ells that extend from the seed coat during development within bells. It was hypothesized that elongating cotton fibers would be responsive to the far- red (FR) to red light (R) photon ratio (FR/R) reflected to developing bells . To test the hypothesis, plants were grown in trickle irrigated field plot s over different colored soil covers that reflected high FR/R and low photo synthetic photon nux (PPF), or low FR/R and high PPF to developing bells. N ewly opened flowers were tagged over three replicate plots of each of four colors. After the flowers were fertilized, randomly selected young bells we re covered with aluminum foil to shield them from light during development Others served as unshielded controls. The FR/R and PPF impinging on develop ing bells affected biomass per area of carpel walls and the amount of FR tr ansmitted into the bells to the developing fibers. Fiber lengths were deter mined after the bulls matured. Fibers in unshielded bells that developed ov er green and red (higher reflected FR/R) soil covers were significantly lon ger than those that developed over aluminum and white (higher reflected PPF ). The difference in length of fiber developed in unshielded versus shielde d bells was greater over green and red than over aluminum and white indicat ing a greater response to increased FR/R than to increased PPF impinging on the developing bells. These results suggest that reflected FR should be co nsidered along with other environmental factors when developing innovative production systems that involve nontraditional row spacing, plant populatio n densities, or soil surface conditions that can affect the photon ratios t o which the developing plants are exposed.