Abstract
ABSTRACT: Cotton cultivation in Brazil tends to occur mostly in the rainy season, and at the time of developing the crop there are often prolonged periods of low solar radiation. The objective of this work was to evaluate the root development of cotton cultivars subjected to shading in the initial phase. The experiment was carried out in a greenhouse, using rhizotrons. The experimental design was a 2x2 factorial in randomized blocks with five replications. The treatments were composed of cotton cultivars TMG 1WS (early) and TMG 8WS (late) and luminosity conditions: non-shaded and shaded (50% reduction of luminosity). There were no interactions between the factors “shading” and “cultivars” for any parameter evaluated. Shading reduced total and lateral root growth from the 21 days after emergence (DAE) and the main root at 24DAE. Shading caused reductions in length (60%), surface (65%), mean diameter (15%), root volume (69%), root dry matter mass (83%) and shoot (64%), as well as decreasing the content (36%) and the accumulation of carbohydrates in the shoot (73%). Shading at early cotton development reduces the shoot carbohydrates production, affecting dry matter accumulation and root growth, and this response is independent of the cultivar.
Highlights
Cotton (Gossypium hirsutum L.) is produced around the world in a variety of environments, including tropical and subtropical regions
After the end of the rainy season, the moisture stored in the soil subsurface would be the main source of water for the plants, and those with a shorter root system would enter into stress earlier
The experiment was conducted in a greenhouse, located at latitude 22°07’04” S, longitude 51°22’04” W and at 432m altitude, at Universidade do Oeste Paulista (UNOESTE), Presidente Prudente, São Paulo, Brazil
Summary
Cotton (Gossypium hirsutum L.) is produced around the world in a variety of environments, including tropical and subtropical regions. Most of the production areas are under tropical savannah climate (Aw - Köppen), as in central Brazil and south - central India. In India, 43% of the cotton area (5.1 million ha) occurs in states under the influence of this climate, and 2/3 of the area are dependent on monsoon rains. Radiation is reduced in the rainy season because of cloudness. After the end of the rainy season, the moisture stored in the soil subsurface would be the main source of water for the plants, and those with a shorter root system would enter into stress earlier. Light is one of the main factors affecting growth and development of plants, since it provides energy for photosynthesis and for the production of carbohydrates. Previous studies have shown the negative effect of reduced radiation availability on flowering and boll development periods on yield and fiber
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