Space and time dependence of temperature and freezing in evergreen leaves

Abstract

Infrared video thermography was used to study space and time dependence of freezing in intact, attached leaves of snow gum (Eucalyptus pauciflora Sieb. ex Spreng.) seedlings. Freezing initiated in the midvein and spread through the apoplast at 10 mm s–1. Freezing of apoplastic water was detected by a local, rapid increase in temperature, and was followed by a slower increase in leaf temperature to the equilibrium freezing temperature as symplastic water moved from cells to extracellular sites of ice formation. The duration of freezing varied with position, leaf thickness and water content. Most of the cellular water in the leaf tip and margins froze quickly, while freezing was slower near the petiole and midvein. Regions that had frozen more rapidly then began to cool more rapidly, producing steep gradients in leaf temperatures and hence also freeze-induced dehydration. Thus, spatial variation in physical properties of leaves could affect the distribution of minimum leaf temperatures, and hence, the distribution and extent of damage due to freeze-induced dehydration. These results are consistent with patterns of freezing damage in autumn when the duration of freezing may be insufficient for the whole leaf to freeze before sunrise, and may explain the general observation of increased leaf water content and thickness with altitude.

A physiologically explicit morphospace for tracheid-based water transport in modern and extinct seed plants

“…During freezing, air is pushed out of solution; larger cells will produce more air when frozen, leading to larger cavitation events. A large literature shows that large conduits are more vulnerable to cavitation than small conduits (Ball et al 2006, Ball et al 2002, Davis et al 1999, Hammel 1967, Sperry and Sullivan 1992, Sucoff 1969. Ice has an extremely low water potential and creates a hydraulic gradient that can dehydrate nearby cells and damage cell membranes (Pearce 2001, Steponkus 1984.…”

Ice Propagation in Dehardened Alpine Plant Species Studied by Infrared Differential Thermal Analysis (IDTA)

“…In earlier studies ice propagation in woody plants (Wisniewski et al, 1997;Workmaster et al, 1999;Carter et al, 2001;Ball et al, 2002;Sekozawa et al, 2004) and graminoids (Pearce and Fuller, 2001;Stier et al, 2003;Wisniewski et al, 2002a) was mainly studied by infrared video thermography (IRVT). IRVT investigations on ice propagation are rather rare for herbaceous plants (Wisniewski et al, 1997(Wisniewski et al, , 2002a, and are lacking totally for alpine plants.…”

Topography influences the distribution of autumn frost damage on trees in a Mediterranean-type Eucalyptus forest

“…The frost-triggered discoloration patterns at the leaf level characterised in this study support patterns of freezing (Ball et al 2002) and pigmentation change (Nicotra et al 2003…”

“…The notably dry leaves of C. calophylla are consistent with frost-induced dehydration following cell rupture (Ball et al 2002). Though these results show that E. marginata and C. calophylla are both highly susceptible to damage from cold temperatures, contrasting leaf-level symptom patterns may be indicative of differing tolerance to the stressor (Boorse et al 1998).…”