© 1989 Heron Publishing—Victoria, Canada
Water and nutrient supply regimes and the water relations of juvenile leaves of Eucalyptus globulus
M. J. Correia (1), F. Torres (2, 3) and J. S. Pereira (2)
1. Universidade do Algarve, C. Gambelas, P-8004 Faro codex, Portugal / 2. Department of Forestry, Instituto Superior de Agronomia, Tapada da Ajuda, P-1399 Lisboa, Portugal / 3. Universidade de Tras os Montes e Alto Douro, 5000 Vila Real, Portugal / Received February 20, 1989
Summary
Pressure–volume analysis was used to study effects of irrigation and fertilization on the water relations of newly expanded
juvenile leaves of Eucalyptus globulus Labill. seedlings growing in Portugal’s Atlantic region. In May, at the beginning of the dry season, fertilization and irrigation
treatments had no significant effects on the water relations parameters investigated. In September, at the end of the dry
season, leaves from non-irrigated plants had a significantly higher apoplasmic water content and a higher dry weight/turgid
weight ratio than leaves of similar physiological age from irrigated trees. The osmotic potential at full turgor and the water
potential at the wilting point were lower in non-irrigated than in irrigated plants. Changes in osmotic potential at full
turgor were negatively correlated with changes in dry weight/turgid weight ratio, suggesting that reductions in osmotic potential
at full turgor were largely the result of decreases in cell size. Fertilization had no detectable effect on these variables
or on leaf tissue bulk modulus of elasticity. Tissue elasticity was also unaffected by irrigation. Independently of water
and nutrient supplies, leaf elasticity was higher and relative water content at the wilting point lower in leaves sampled
in May than in leaves sampled in September. In non-irrigated plants, leaves sampled in September had a lower tissue elasticity
and a lower osmotic potential at full turgor than leaves sampled in May, indicating that leaves produced at the end of the
dry season generate lower water potentials as turgor is lost than leaves expanded early in the season.
