Foi realizado um estudo com o objetivo avaliar as trocas gasosas foliares e o crescimento de plantas jovens de Protium heptaphyllum March submetidas ao alagamento do solo em dois ambientes de luz. Foram realizados dois experimentos independentes e simultâneos, onde as plantas foram cultivadas em dois níveis de sombreamento: sombra moderada (SM: 15,3 a 22,9 mol fótons m-2 d-1) e sombra densa (SD: 3,2 a 5,2 mol fótons m-2 d-1). Metade das plantas em cada ambiente de luz foi alagada e a outra metade mantida como controle. Avaliou-se a taxa fotossintética líquida (A) a condutância estomática ao vapor de água (gs), as razões de massa de folhas (RMF), caules (RMC) e raízes (RMR), a taxa de crescimento relativo (TCR) e a taxa assimilatória líquida (TAL). Os maiores valores de TCR e TAL foram verificados em ambiente de SM. As plantas submetidas ao alagamento do solo apresentaram diminuições significativas de A e gs, as quais foram mais pronunciadas na SM. Além disso, em SM, o alagamento provocou aumentos na RMF e RMC e diminuição significativa da RMR. Em SD, a RMF aumentou, a RMC diminuiu e a RMR não foi afetada. Plantas jovens de P. heptaphyllum apresentaram tolerância ao alagamento temporário, demonstrando que a espécie pode ser utilizada em programas de restauração de matas ciliares degradadas.
Leaf gas exchange and growth of young plants of Protium heptaphyllum March subject to soil flooding in two light environments was studied. Two independent and simultaneous experiments were conducted, in which plants were cultivated into two light environments: moderate shade (SM: 15.3 to 22.9 mol photons m-2 d-1) and dense shade (SD: 3.2 to 5.2 mol photons m-2 d-1). Half of the plants in each light environment were flooded and the other half was kept as control. We evaluated the net photosynthetic rate (A); stomatal conductance to water vapor (gs); the mass ratios of leaves (RMF), stems (RMC) and roots (RMR); relative growth rate (TCR) and the net assimilation rate (TAL). Plants subjected to soil flooding showed significant decreases of A and gs, which were most pronounced in the SM. Flooding induced increases in RMF and RMC and a significant decrease in RMR, in SM. In SD, the RMF improved, RMC decreased and RMR was not affected. The highest mean values of RGR and TAL were observed in SM. P. heptaphyllum seedlings can tolerate soil flooding for a time and can be used in riparian forests restoration programs.
