Abstract The internal structure of seeds is relevant to germination, seedling establishment, and early plant growth. The objective of this work was to evaluate whether internal seed structure can influence germination and initial growth in four native woody species of the Cerrado. The species chosen for this study were Anadenanthera falcata, Stryphnodendron adstringens, Stryphnodendron polyphyllum, and Tabebuia aurea. Seeds were dissected to evaluate: the lengths of the hypocotyl-radicular axis, the epicotyl and the embryonic axis, mass of the cotyledons and the embryonic axis, and eophyll number (preformed organs). Another group of seeds was germinated in a greenhouse for sixty days to verify the emergence of the epicotyl, eophylls, metaphylls, and to measure seedling biomass. Only A. falcata presented a plumule with differentiated eophylls. Anadenanthera falcata germinated before the other species in the greenhouse and had faster epicotyl and leaf emergence. Possibly, the presence of eophylls inside the seed enabled A. falcata seedlings to carry out photosynthesis, grow faster, and accumulate more aerial biomass than the other species soon after emergence. The presence of eophylls in a differentiated embryo (as in A. falcata) may hasten germination and favour seedling establishment.

ABSTRACT Changes in atmospheric CO2 levels are accompanied by ecological interactions involving other environmental factors, such as drought, which can severely alter the water balance of plants, thereby influencing sap flow, gas exchange, and plant growth. The objective of this study was to evaluate the water use economy, leaf gas exchange, and growth of young plants of the species Lafoensia pacari subjected to high concentrations of atmospheric CO2 ([CO2]) and soil water deficit. Increased vapor pressure deficit was observed from 1200 to 1800 hours. Plants under elevated [CO2] exhibited increased leaf photosynthesis, resulting in improved growth. Specific leaf area was lower in plants under high [CO2], mainly after soil water deficit treatment. Daily irrigated plants growing under ambient [CO2] had higher stem sap flow velocity (cm h-1) and hourly sap flow (kg h-1), mainly during the hottest hours of the day, than plants under high [CO2]. Improved water use by plants growing under high [CO2] may result in increased availability of water in the soil, partially offsetting future drought events and extending the growth period.