Leaf characteristics and chlorophyll concentration of Schyzolobium parahybum and Hymenaea stilbocarpa seedlings grown in different light regimes.

Light in the understory of a forest varies not only with season and solar elevation but also with vegetation dynamics. Seedlings of Schyzolobium parahybum (Vell) Blake, a fast-growing pioneer species, and Hymenaea stilbocarpa L., a slow-growing shade-tolerant species, were grown in pots for 90 days in a forest canopy gap (full sunlight) or in semi-shade (about 44% of full sunlight) beneath the canopy of a secondary forest. Both sites were located in Itaguai, RJ State, Brazil. Subsequently, half the seedlings grown in the canopy gap were moved to semi-shade and half the seedlings grown in semi- shade were moved to the canopy gap. After a further 90 days, seedling dry weight, height, leaf area, specific leaf area, leaf area ratio and concentration of chlorophyll a and b were measured. In response to increased irradiance, Schyzolobium parahybum responded by producing more leaf area, whereas Hymenaea stilbocarpa responded by increasing leaf mass per unit area and chlorophyll a concentration.