© 1995 Heron Publishing—Victoria, Canada
Frost resistance and susceptibility to ice formation during natural hardening in relation to leaf anatomy in three evergreen
tree species from New Zealand
G. Neuner (1, 3) and P. Bannister (2)
1. Institut für Botanik, Abteilung Allgemeine Botanik, Sternwartestrasse 15, 6020 Innsbruck, Austria / 2. Department of Botany, University of Otago, P.O. Box 56, Dunedin, New Zealand / 3. Author to whom correspondence should be addressed / Received September 13, 1994
Summary
Foliar frost resistance of three endemic New Zealand land trees, Nothofagus menziesii (Hook. f.) Oerst. (Fagaceae), Pittosporum eugenioides A. Cunn. (Pittosporaceae) and Griselinia littoralis Forst. f. (Cornaceae), was examined as the trees hardened from late summer to midwinter in a lowland forest site. The lowest
temperatures causing 50% damage (LT50) occurred in late winter and were similar to those recorded for other forest trees native to New Zealand (–11.7 °C in N. menziesii, –10.7 °C in P. eugenioides, and –10.6 °C in G. littoralis). All three species hardened by 4–7 °C, with G. littoralis showing the least frost resistance in summer and hence the greatest degree of hardening. Thermal analysis during freezing
indicated that all three species became more tolerant of extracellular ice formation in winter. Measurements of chlorophyll
a fluorescence correlated well with visible injury. The differing patterns of frost damage development in the three species
were related to leaf anatomy: visible injury was localized within the small compartments formed by the highly septate leaves
of the most resistant species, N. menziesii, and was somewhat localized in the partially septate leaves of P. eugenioides, whereas damage could be initiated anywhere in the aseptate leaves of G. littoralis,which was the least frost resistant species, particularly in summer.
Keywords:
chlorophyll a fluorescence, differential thermal analysis, Griselinia, leaf anatomy, Nothofagus, Pittosporum.
