Abstract
We studied the relationship between the increase in resistance to Pythium snow rot provided by cold acclimation and changes in phenylalanine ammonia-lyase (PAL) activity, and the contents of total phenol, lignin and sugar. A significant increase in the resistance was observed after one week of cold acclimation treatment. The PAL activity increased one week after inoculation with a Pythium snow rot pathogen, P. paddicum. The increase of PAL activity under the cold acclimation was greater than that under the untreated control. The suppression of PAL activity realized by using α-aminooxy-β-phenylpropionic acid (AOPP) and α-aminooxy acetic acid (AOA) reduced the resistance induced by the cold acclimation. These results suggest that PAL plays an important role in the cold acclimation-induced resistance to spread of symptoms. The total phenol and lignin content increased after the cold acclimation. The methanol soluble sugar and water soluble sugar content of leaf blades increased under the cold acclimation, however, sugar content of cell wall remained unchanged.
