Effect of light intensity on early growth of <i>Cecropia glazioui</i> Snethlage (Cecropiaceae)<p>

Abstract

Previous study working with plants growing under polyethylene screen showed the response of Cecropia glazioui seedlings to light variations from 2% to 50% of full sun. The present study addressed the following questions related to the response of C. glazioui seedlings growing under polyethylene screen receiving 50% to 100% of full sun and under forest shadow. The aim of this work was to verify the following questions: 1) Do the seedlings present morphological and physiological adjustment with light intensities above 50% of the total solar light? 2) Do the light intensities above 50% of the full solar light inhibit the growth of the seedlings? 3) What are the alterations in the growth verified in seedlings to the variation in the amount of light? 4) Do the seedlings respond in the same way to the shadow done by polyethylene screen and forest? To verify these questions the seedlings were put in plastic bags of 18 x 13cm, containing forest soil and organic compound from recycling waste (1:1). The plants were put under 100%, 70% and 50% of solar light, done by polyethylene covering, and in forest border, small gap and closed forest. The results showed that the species studied had the same kind of responses both under artificial ant natural shadow. The species didn't present morphological or physiological adjustments when the intensity of light varied above 50% of solar light. Also the light intensity above 50% of the solar light didn't inhibit the growth of the species. The main significant alterations, verified in the growth, in agreement with the increase in the amount of light were: decrease of root/shoot (R/S), of specific leaf area (SLA) and of leaf area ratio (LAR) and of the height of the stem and increase of the photosynthetic capacity.