OSMOTIC ADJUSTMENT AND ITS USE AS A SELECTION CRITERION IN EUCALYPTUSSEEDLINGS

Osmotic adjustment was studied in 6-month-old seedlings of Eucalyptus camaldulensis Dehnh., Eucalyptus tereticornis Smith, Eucalyptus vimina lis Labill., and Eucalyptus grandis Hill ex Maiden. Because osmotic ad justment is related to water-stress tolerance, it can be used as a sel ection criterion of material adapted to drought. Half of the individua ls of each species were submitted gradually to water stress, while the rest were maintained in soil at field capacity. Twenty-five days late r the effect of stress on the development of osmotic adjustment was an alyzed. All species had adjusted osmotically. The lowest osmotic adjus tment was observed in E. camaldulensis and E. grandis (14.1% and 15.2% , respectively). Eucalyptus viminalis and E. tereticornis had values o f 32.3% and 41.9%, respectively. Our results demonstrate that species differ significantly in their extent of osmotic adjustment under droug ht stress, and that it is possible to use this inductive plant feature as one of the criteria to select, during early developmental stages, Eucalyptus genotypes adapted to drought-prone environments. Some phylo genetic considerations are presented.