Leaf water potential and gas exchange of eucalypt clonal seedlings to leaf solar protectant

This experiment was carried out in acclimatized greenhouses with seedlings of two hybrid clones of Eucalyptus urophylla × Eucalyptus grandis. A sunscreen protector consisting of 62.5% calcium carbonate was sprayed on the seedlings at weekly intervals. Water stress was induced by suspending irrigation until the soil reached 30% available water and water was then replaced so that it returned to field capacity. Gas exchange and leaf water status were measured after 50 days. The experiment was set up in a 4 × 2 factorial randomized block design in four distinct environments: (1) temperatures less than 21.2 °C and vapor pressure deficit of 0.15 kPa; (2) intermediate temperatures of 24.2 °C and vapor pressure deficit of 0.69 kPa; (3) high temperatures of 27.0 °C and high vapor pressure deficit of 1.4 kPa; and, (4) high temperature of 27.0 °C and vapor pressure deficit below 1.10 kPa. Two leaf sun protector treatments were used, with five replications each. High atmospheric demand acted as a stress factor for the seedlings during the initial growth phase. Applications of leaf sunscreen protector provided beneficial effects in maintaining optimum water status and gas exchanges of the plants under water stress.