Does Ceiba pentandra (Malvaceae) a light demanding species succumb under deep shading?

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Sumauma (Ceiba pentandra) is a fast-growing and light-demanding species that occurs across a wide rainfall range in tropical regions, but it is still unclear how it performs under shading. This work aimed to evaluate leaf traits and biomass allocation of sumauma seedlings in response to different levels of artificial shadings. After a strengthening period of 14 months (at moderate light), the seedlings were submitted to three shading levels for 580 days: moderate shading (T1: irradiance of 5.59 mol m⁻² day⁻¹), strong shading (T2: 1.29 mol m⁻² day⁻¹), and deep shading (T3: 0.14 mol m⁻² day⁻¹). The control (T0) was seedlings under direct sunlight (15.65 mol m⁻² day⁻¹). Parameters evaluated were plant growth, biomass allocation to plant organs and leaf traits. Growth and biomass accumulation enhanced with a rise in irradiance, being maximum under direct sunlight and null under deep shading. Sumauma did not succumb under deep shading, as it was able to endure deep shading for 19 months. Under deep shading, the seedlings allocated just a little amount of biomass to leaves and greatly reduced leaf thickness. The whole-plant compensation point was estimated to be 1.0 mol m⁻² day⁻¹. We concluded that pre-strengthened sumauma seedlings may endure deep shading. These traits combined with the high growth rates of this tree under full sunlight make of sumauma a promising candidate to be tested in reforestation projects.