Effect of continuous and intermittent shade on carbohydrate accumulation and root growth in cotton

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Light restriction is one of the environmental factors that most limits cotton (Gossypium hirsutum L.) growth and production in tropical regions, due to the plant exposure to cloudy days with low radiation availability. This study evaluated the initial development of cotton root growth under intermittent shade intervals of 2 (2-d), 4 (4-d), and 8 (8-d) days, continuous shade and no-shade (control) treatments, using a black screen to reduce light intensity by 50%. Continuous shade reduced the total root length by 30% compared to the control. Decreases in root length were verified on the thinnest roots (0-0.5 mm) and were approximately 47% in the shaded and 2-d shaded treatments, 33.8% with an 8-d shade interval, and 11% with a 4-d shade interval. Plants shaded continuously and under the 2-d-shade interval showed higher height, but fewer leaves. Continuous shading and 4-d shade interval decreased the plant biomass and the carbohydrate accumulation on leaves and squares. It was concluded that continuous or intermittent 4-d shade reduces carbohydrate content on leaves and stems, continuous shading reduces cotton root length, and the root length of thinner roots (0-0.5 mm) is affected by continuous or 2-d intermittent shade.