MORPHOLOGICAL AND PHYSIOLOGICAL COMPARISONS OF CLONAL LINES OF EUCALYPTUS-CAMALDULENSIS .2. RESPONSES TO WATERLOGGING SALINITY AND ALKALINITY/

Eucalyptus camaldulensis Dehnh. has previously been shown to survive a nd grow in waterlogged, highly saline and highly alkaline soils. The a bility of six clones from five provenances of E. camaldulensis to prod uce biomass and utilise water, and the processes of stomatal conductan ce and gas exchange under stress conditions was examined under control led conditions in a glasshouse. A clone originally from Wooramel, West ern Australia (M80) produced the largest total plant biomass, the grea test total leaf area and greatest total root dry weight under conditio ns of waterlogging and gradually increasing salinity. A second clone f rom Wooramel (M16), however, tended to be among the least productive o f the clones under this stress, indicating the wide potential variatio n in stress tolerance of trees from a single provenance. The response of clones to alkalinity stress was comparable to that measured under w aterlogging/salinity stress. Water use was closely related to biomass production. Leaves produced while under salinity and alkalinity stress were comparable in ion content to those produced prior to the test co nditions. An ability to control uptake by roots or limit ion transport to leaf tissues were hypothesised as controlling physiological functi ons resulting in tolerance to severe soil ion imbalances in this speci es. The impact of solution conductivity on stomatal conductance and wa ter use, secondarily affected photosynthetic rates in these clones of E. camaldulensis. Tolerance of extreme conditions provides the opportu nity to use these genotypes to reclaim damaged agricultural landscapes and mine spoils of high soil solution ion concentrations.