Alibertia edulis Rich. is a native species of the Brazilian Cerrado and can be used for reforestation of degraded areas. In addition, it produces edible fruits. The objective of this study was to evaluate the effect of substrates and water levels on the emergence, initial growth, and quality of seedling of A. edulis. The substrates tested were: latosol (L), latosol + sand (L + S = 1:1), latosol + sand + chicken manure (L + S1 + CM = 1:1:0,5), latosol + sand + chicken manure (L + S2 + CM = 1:2:0,5), and latosol + commercial substrate (L + C = 1:1); and the water retention capacities (WRC) tested were: 25, 50, 75, and 100%. The experiment was carried through in a completely randomized design and subdivided into a plot scheme, in which the plots represented water availability and the subplots represented the substrates. Latosol + commercial substrate at 100% of WRC provided the best conditions for emergence, initial growth and formation of seedlings of A. edulis. Sowing in the substrate Dystroferric Red Latosol isolated at 25% of WRC should not be used for the formation of seedlings of this species.

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The aim of this research was to evaluate the effect of abscisic acid (ABA) on gas exchange and the activity of antioxidant enzymes of Ormosia arborea (Vell.) Harms seedlings under water deficit and its influence on the recovery potential of the seedlings. The experiment was conducted using four treatments, being daily irrigation or water restriction without and with 10 μM ABA. Seedlings under water deficit + ABA showed greater adjustment to drought, and when re-irrigated, they restored photosynthetic metabolism and water potential. ABA minimizes the reduction in the photosynthetic metabolism and water potential of the leaf, however, it does not increase the antioxidant activity of the O. arborea seedlings under water deficit. These results suggest that this species exhibits plasticity, which enables it to survive also in environments subjected to temporary water deficit regardless of the supplementation of ABA. We suggest that other doses of ABA be researched to expand the beneficial effect of ABA on this species.

The aluminium at toxic levels causes biochemical and physiological damage that inhibits plant growth and limits productivity. Root growth, chlorophyll a fluorescence, and enzyme activity of four accessions of Jatropha curcas were evaluated under cultivation conditions with different levels of aluminium. The experimental design was completely randomized with a split-split-plot design, in which the plots included four levels of aluminium in the soil (0.0, 8.2, 16.5, and 24.0 mmolc dm-3), the split-plot were the four accessions of J. curcas seeds (P1 = Dourados, MS; P2 = Montes Claros, MG; P3 = Alta Floresta, MT; P4 = Petrolina, PE), and split-split-plot in all four times of evaluation (25, 50, 75, and 100 days after emergence - DAE) with four replications. At 100 DAE were evaluated the curve of transient chlorophyll a fluorescence (OJIP) and enzyme activity, the treatments were arranged in split-plot, being four levels of aluminium in the soil and the four accesses of J. curcas. Six readings for the OJIP curve and three repetitions for enzymatic analysis were conducted. The characteristics of gas exchange and chlorophyll a fluorescence indicated that doses above 8.2 accentuated aluminium stress on plants from all accessions. The reduced efficiency of carboxylation of Rubisco and the results of the OJIP test indicated that photochemical efficiency of all varieties was decreased. The activity of the enzymes catalase, peroxidase, and superoxide dismutase was higher in the presence of aluminium for the accessions P3-Alta Floresta and P4-Petrolina. Our results indicate the greater tolerance of these accesses to aluminium stress conditions.

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