New Zealand Journal of Botany abstract

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The winter hardening and foliar frost resistance of some New Zealand species of Pittosporum

PETER BANNISTER
CATHERINE M. COLHOUN
PAULA E. JAMESON*

Department of Botany
University of Otago
P.O. Box 56
Dunedin, New Zealand
* Present address: Department of Plant Biology and Biotechnology, Massey University, Private Bag 11-222, Palmerston North, New Zealand

Abstract  The foliar frost resistance of Pittosporum eugenioides, P. obcordatum, P. tenuifolium, and P. crassifolium increased from -6deg.C to -8deg.C in March and April to between -9deg.C and -10deg.C in July. Leaves of P. obcordatum had the lowest frost resistance (-7deg.C) in April, but showed the highest resistance (<-10deg.C) in July. The foliar frost resistance of P. eugenioides is greater than that previously recorded, similar to that of P. crassifolium and P. tenuifolium, and is consistent with the widespread distribution of this species within New Zealand. The relatively high frost resistance of leaves of P. obcordatum is in accord with its occurrence in frost-prone habitats.

Seedlings of P. eugenioides subjected to short days and night-time temperatures around 0deg.C became about 1deg.C more frost resistant than untreated seedlings in autumn (April and May). The maximum frost resistance (-11deg.C) attained by treated seedlings of this species was no greater than that of untreated seedlings, but was 2deg.C greater than that of adult plants in the field. The youngest and oldest leaves of seedlings were less frost resistant than leaves of intermediate age.

Keywords  frost resistance; hardening; acclimation; Pittosporum; New Zealand

New Zealand Journal of Botany, 1995, Vol. 33: 409-414

0028-825X/95/3303-0409 $2.50/0 (c) The Royal Society of New Zealand 1995

PDF file of entire paper: medium quality (342K); (scanned from paper original: notes about this process)

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