Effects of frost on leaf gas exchange and rubisco activity in the subalpine species Eucalyptus pauciflora ssp pauciflora Sieb. ex Spreng. (Snow gum)

Leaves of the evergreen Eucalyptus pauciflora (as well as of E. delegatensi s) were studied at the plants' natural, subalpine field sites. Frost down t o -10 degrees C only temporarily affected leaf gas exchange which fully rec overed after a few days without frost. Potential rubisco activity was also maintained over the frost period. The response of net photosynthesis to lea f temperature, measured in the field, differed only slightly from that in s ummer and autumn with a temperature optimum ranging from 20 to 25 degrees C contrasting previous observations from laboratory studies and contrasting the situation in the European Alps.