This study aimed to verify how morpho-physiological characteristics differ between species of the Caatinga with different light requirements for initial growth, and had the hypothesis that P. stipulacea is light-demanding and A. colubrina is shade-tolerant in the early stages of life. We conducted a randomized block experiment in which seedlings of both species were subjected to treatments of full sun, 50%, 70% and 90% shade for six months. We evaluated morphological (height, diameter, number of leaves and biomass allocation) and physiological (a, b and total chlorophyll content, and ratio of chlorophyll a/b) features. The results showed that these species have different light requirements during early growth. Seedlings of P. stipulacea showed a higher relative growth rate and larger diameter when growing in full sun, and a lower root/shoot ratio and lower total chlorophyll content when compared to seedlings of A. colubrina. The best results were for P. stipulacea in full sun and A. colubrina at intermediate levels of shade, which corroborate the hypothesis of this work and are consistent with where each species grows.
biomass; chlorophyll; light-demanding; shade-tolerant
