| Popis: |
The annual course of frost resistance and free proline content was studied in leaves at different stages of development of a woody species (Nothofagus dombeyi) from Southern Chile. The freezing resistance reached a minimum in late spring or summer and a maximum in the autumn-winter period. Adult and juvenile trees showed a similar degree of resistance; meanwhile, cold resistance was maximum at the seedling stage. Free proline levels and frost resistance in leaves changed throughout the seasonal cycle, increasing in winter and decreasing in summer. Artificial hardening caused changes in amino acid content of leaves; while valine, proline, lysine, histidine, serine and alanine increased upon hardening, aspartic acid, glutamic acid and arginine decreased. The nature of cold-induced metabolic adjustments is discussed as well as its ecological significance. |
