Effect of seed size and growing media water availability on early seedling growth in Eucalyptus globulus

This work shows that it is possible to control seedlings growth in containers in order to study nursery management and for testing of new progenies selected from a breeding program. Seeds of Eucalyptus globulus Labill. were sorted by size, sown in containers and watered either daily by aspersion or by five different automatic watering treatments controlled by microtensiometers that allowed control of water to the seedlings. The larger seed size showed a higher germination capacity, although treatments with excess deficit of water delayed the germination response. Increasing water stress significantly affected plant height, with differences due to seed sizes. When compared with well watered plants (−1.8kPa), dry matter was reduced about 50% in −6.3kPa treated plants. Drought treatment (−6.3kPa) also caused a substantial reduction in leaf area. Moreover, a small seed size resulted in taller plants with higher root and shoot dry masses. Thus, the differences in morphological response according to water availability and the size of seeds may indicate a genetic effect that controls adaptation of the plant to external stress.