Frost resistance of the New Zealand narrow‐leaved snow tussock grass,Chionochloa rigida

Abstract

The frost resistance of tillers of Chionochloa rigida was measured at various dates and locations from late winter (August 2004) to early summer (December 2004). Frost resistance changed in accord with season, geographic location, and position on the tiller and was strongly related to estimated minimum temperatures at the date and site of collection. Foliar frost resistance was -21°C in late winter and -10°C in summer; leaf sheaths and bases were less frost resistance than laminas. The strong dependence on temperature suggests that the frost resistance of C. rigida would adjust to prevailing temperatures during a period of global warming, although it might render C. rigida more susceptible to episodic frosts. On a global scale, C. rigida is less frost resistant than many temperate pasture grasses and cereals and shows some affinity with tropical alpine vegetation.

Foliar freezing resistance of Australian alpine plants over the growing season

“…However, this process was only seen in one species (Craspedia aurantia, early snowmelt area, open heath) and most of the other species showed no significant directional change in resistance throughout the season, although most species were also able to resist temperatures lower than the recorded minima (Table 1). Extending the study through to the first snowfalls of the subsequent season may have shown a different acclimation response, as the seasonal course of freezing resistance may be determined by several interacting environmental factors including photoperiod, high and low temperature extremes and soil moisture (Loik & Redar 2003;Loik et al 2004;Bannister 2005;Bannister et al 2005;Sierra-Almeida et al 2009). In support of this, the most marked increases in freezing resistance measured by Bannister et al (2005) occurred after the March (autumn) equinox.…”

“…Following pre-treatment, three leaves from three replicate plants of each species were subjected to one of four temperature treatments (-4°C, -10°C, -16°C and -23°C) for 8 h using thermostatically controlled freezers. The range of temperatures was selected to be comparable with the methods used in studies of New Zealand alpine plant freezing tolerances (Bannister 2005;Bannister et al 2005). This method of direct rather than gradual cooling thereby measures the current freezing resistance rather than the hardening capacity of plant material (Larcher et al 2010).…”

“…In support of this, the most marked increases in freezing resistance measured by Bannister et al (2005) occurred after the March (autumn) equinox. Extending the study through to the first snowfalls of the subsequent season may have shown a different acclimation response, as the seasonal course of freezing resistance may be determined by several interacting environmental factors including photoperiod, high and low temperature extremes and soil moisture (Loik & Redar 2003;Loik et al 2004;Bannister 2005;Bannister et al 2005;Sierra-Almeida et al 2009).…”

Comparative winter frost resistance of plant species from southern Africa, Australia, New Zealand, and South America grown in a common environment (Dunedin, New Zealand)

“…A teaching-PAM chlorophyll fluorometer (Walz, Effeltrich, Germany) was used to determine Fv/F m (the ratio of variable to maximum fluorescence of the sample) of dark-adapted leaves (Bolhar-Nordenkampf et al 1989). The temperature at 50% of the maximum Fv/F m for each species (LT 50 ) was determined by linear interpolation using the temperature of the highest F v /F m under 50% of F,â nd the lowest Fv/F m over 50% F max (Bannister 2005;Bannister et al 2005). Damage was also estimated visually and the temperature causing 50% damage was determined by linear interpolation .…”

“…The precise provenance of species grown in the Botanic Garden is largely unknown and the capacity of a particular species to harden or deharden is likely to reflect its origins (Sakai & Larcher 1987). Both short days and low temperatures induce greater frost resistance (Bannister 2005;Bannister et al 2005) and the current investigation was conducted during the shortest and coldest days of winter (June, July). Species from different latitudes and altitudes would experience day lengths and temperatures that differed from those in the Botanic Garden.…”