Avoidance and Tolerance Mechanisms for coping with low water environments.
| Strategy | Mechanism(s) | Growth | Examples |
|---|---|---|---|
| Drought avoidance | Grow where and when water is available | Unaffected until water is limiting | Eucalyptus regnans, E. camaldulensis, E. marginata |
| Drought tolerance by improved water status | Increased rooting volume | Improved | Acacia mearnsii, E. camaldulensis, E. clelandii, E. trivalvis |
| Increased root density | Improved | E. camaldulensis, Acacia mearnsii | |
| Good stomatal control | Usually reduced | Casuarina littoralis, E. calophylla, Eremophila macgillivrayi, Pittosporum phylliraeoides, Myoporum floribundum | |
| Capacity for osmotic adjustment | Usually reduced | Atriplex nummularia, E. viminalis | |
| Reduced leaf surface area | Usually reduced | Acacia melanoxylon, Acacia mearnsii, E. clavigera, E. grandiflora, E. brachyandra | |
| Larger root:shoot ratio | Usually reduced | E. camaldulensis, E. marginata, Acacia mearnsii | |
| Drought tolerance by maintaining cell volume | More elastic cell walls | Usually reduced | Acacia aneura |
| Dehydration tolerance | Cells and physiology unaffected by reduced water content | Usually reduced or restricted | E. rossii, E. viminalis, Acacia aneura |
Note: Columns 1–3 of this table are extended and modified from Atwell et al. 1999. Column 4 is based on the author’s experience with these Australian species.