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Revta brasil. Bot., São Paulo, V.23, n.3, p.225-230, set. 2000

Efeitos da deficiência de água em plantas de Euterpe oleracea (açaí)
MARIA ELISA RIBEIRO CALBO1,3 e JOSÉ ANTÔNIO P.V. DE MORAES2
(recebido em 1 de setembro de 1999; aceito em 10 de março de 2000)
ABSTRACT - (Effect of water deficit in Euterpe oleracea (açaí)). The water stress resistance of young açai plants Euterpe oleracea
Mart. was determined in four-month-old plants, cultivated in punched black plastic bags filled with 7 kg of soil. The experiment was carried out in a greenhouse and irrigation was suspended until the photosynthesis drops to zero, after this moment daily irrigation was applied. During this dehydration period photosynthesis, stomatal conductance, and transpiration were measured daily. Small reductions in stomatal conductance, transpiration and photosynthesis were observed from the tenth day and became more pronounced with time.
The photosynthetic rate fell to half of its maximum value when the water potential reached -1.9 MPa. After withholding irrigation for
61 days, the water stress was severe enough to reduce photosynthesis to zero; at this time the leaf water potential was -2.5 MPa. Recovery of photosynthesis, stomatal conductance and transpiration started one day after rewatering and reached values similar to the control after two weeks of daily irrigation (rehydration). An osmotic potential reduction was calculated from leaf pressure-volume data, as a result the estimated osmotic adjustment was 0.29 MPa at zero turgor and 0.36 MPa at full turgor. Such osmotic adjustment indicates an açai adaptation mechanism to moderate water stress.
RESUMO - (Efeitos da deficiência de água em plantas de Euterpe oleracea (açaí)). A resistência de plantas jovens de açaí (Euterpe oleracea Mart.) à deficiência de água foi determinada em plantas de quatro meses de idade cultivadas em sacos plásticos perfurados contendo 7 kg de terra. O experimento foi conduzido em casa de