New Zealand Journal of Botany abstracts

---

Are juvenile forms of New Zealand heteroblastic trees more resistant to water loss than their mature counterparts?

Heather E. Darrow
Peter Bannister*
David J. Burritt

Department of Botany
University of Otago
P.O. Box 56
Dunedin, New Zealand

Paula E. Jameson

Institute of Molecular Sciences
Massey University
Private Bag 11 222
Palmerston North, New Zealand
*Author for correspondence. Email: peter@planta.otago.ac.nz

Abstract  One of the theories for the evolution of divaricating shrubs and juvenile forms of heteroblastic woody plants suggests that these forms were selected for resistance to water loss. We examined the water relations and carbon isotope ratios (δ¹³C) of excised shoots from juvenile and mature forms of one homoblastic species, seven heteroblastic species, and the divaricating shrub Coprosma rotundifolia. Shoots from the juvenile divaricate forms and C. rotundifolia showed responses (relatively high rates of water loss, high osmotic water contents, more negative δ¹³C, elastic cell walls and low water contents at turgor loss) characteristic of water spenders. Mature and juvenile forms of Pittosporum eugenioides and Pseudopanax crassifolius and mature Carpodetus serratus showed the opposite characteristics. The ordination of these characteristics suggested that juvenile forms of P. eugenioides, Streblus microphylllus, Sophora microphylla, and Carpodetus serratus were more water-spending than their mature forms, whilst juvenile forms of Pseudopanax crassifolius, Hoheria angustifolia, and Plagianthus regius tended to be somewhat less water-spending than their mature forms. Our results do not support the hypothesis that juvenile forms of heteroblastic trees are more resistant to water loss than their mature counterparts. We suggest that forms with a divaricating habit produce a micro-environment within the shrub that favours small leaves, with relatively high leaf conductance, water loss, and CO₂ assimilation rates, that also may be partially adapted to shade.

Keywords  climate; drought; desiccation; water relations; heteroblasty; xeromorphy; divaricating shrubs; juvenile; mature; Pseudopanax crassifolius; Streblus heterophyllus; Pittosporum eugenioides; Sophora microphylla; Carpodetus serratus; Hoheria angustifolia; Hoheria populnea; Plagianthus regius; New Zealand

B01032 Received 12 July 2001; accepted 25 February 2002
New Zealand Journal of Botany, 2002, Vol. 40: 313–325
0028–825X/02/4002–0313 $7.00 © The Royal Society of New Zealand 2002

PDF file of entire paper: Print-quality (126K)

---

This year's abstracts | Journal home page | All abstracts | Publishing home page