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 e levation but also with vegetation dynamics. Seedlings of Schyzolobium parah ybum (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 th e 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 w eight, height, leaf area, specific leaf area, leaf area ratio and concentra tion of chlorophyll a and b were measured. In response to increased irradia nce, Schyzolobium parahybum responded by producing more leaf area, whereas Hymenaea stilbocarpa responded by increasing leaf mass per unit area and ch lorophyll a concentration.