Protective enzymes against activated oxygen species in wheat (Triticum aestivum L.) seedlings: Responses to cold acclimation

When plants are exposed to low temperatures, they undergo changes in the ac tivities of some of the enzymes that belong to important metabolic pathways . In order to understand if and how the enzymes of the antioxidant systems are involved in the cold acclimation process and during recovery from freez ing, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX) activi ties were analysed. Triticum aestivum L. (c. vs. Brasilia and Eridano) seed lings were grown at 24/22 degrees C (day/night temperatures) for control tr eatment and at 12/5 degrees C to induce cold acclimation, while freezing tr eatment was performed at -4 degrees C. Significant differences in activity between control and acclimated seedling s were observed for all of the enzymes studied except for catalase in leave s. No clear differences were found when comparing the two genotypes. After being exposed to freezing temperatures, the activities of enzymes wer e compared with those before treatment and the results were expressed as pe rcentage of activation. Superoxide dismutase and catalase enzymes were foun d to be activated more in cold acclimated than ill control leaves, while th e opposite was observed for roots. Peroxidases proved to be activated more both in leaves and roots of control seedlings. Interesting differences afte r exposure to freezing temperatures were also found between the two cultiva rs analysed.