Gas exchange and photosynthetic activity in Hancornia speciosa gomes seedlings under water deficit conditions and during rehydration

Resumo

Considering the wide distribution of Hancornia speciosa Gomes in the Brazilian savanna, environment with irregular distribution of rainfall, it is believed that their seedlings can be cultivated for a few days under water restriction, information that can stimulate the use of this species in restoration or planting for sustainable exploration programs. The present study evaluated the gas exchange and photosynthetic activities of H. speciosa seedlings and examined their tolerance to water deficit and their metabolic recovery after rehydration. We evaluated the photosynthetic rate, internal carbon concentration, transpiration rate, stomatal conductance, water-use efficiency, photosystem II quantum efficiency (Fv/Fm), instantaneous carboxylation efficiency, chlorophyll index, and recuperation potential of H. speciosa seedlings after rehydration. Twelve month-old seedlings were used and maintained at 70% of their soil water retention capacity. Data was collected 7, 10, 12, 14, 16, 18, 20, 23, 31, 33, 35, 37, 42, 44, 46, and 48 days after suspending irrigation; irrigation was reinitiated when the photosynthetic rate approached zero. Water deficit conditions reduced all of the parameters evaluated except the chlorophyll index; stressed seedlings required 42 days for the photosynthetic rate to reach zero, but photosynthetic equilibrium was reestablished just five days after rehydration. This temporary water deficiency did not cause any permanent deleterious effects on the photosynthetic apparatus of the seedlings.