Stress related changes in the architecture of seedlings of three provenances ofEucalyptus camaldulensis Dehnh

Abscisic acid (10^?4M) applied via absorbent discs bound to the stems of 6 wk oldE. camaldulensis seedlings caused changes in leaf shape and orientation similar to those induced by nutritional and water stress. Seedlings from the driest provenance, Tennant Creek, were more responsive to ABA than seedlings from the wettest provenance, Katherine, and the response of Petford seedlings was intermediate. Likewise, Tennant Creek seedlings were most, and Katherine seedlings least, responsive to water and/or nutritional stress. Seedlings that responded to the application of ABA produced prematurely strengthened, linear leaves with the lamina rotated from horizontal to vertical. The ability of Tennant Creek seedlings to readily assume this form may be a specific adaptation for the particularly difficult conditions in their natural environment.