Hence, it appears fairly straightforward that the different nocturnal temperature regimes in the two regions led to evolution of the two different strategies, one taking the risk and obtaining more productivity and the other one avoiding the risk on account of the loss of some productivity. Indeed Table 12.2 suggests that the African Senecio keniodendron has a much lower annual productivity than the Andean Es-peletias (Rada et al. 1985).
Interestingly, Lipp et al. (1994) note that in species growing at high elevations in Hawai'i features of both adaptive strategies are combined and a complete suite of
characteristics with either strict tolerance or avoidance of extracellular ice formation is not expressed. Five species were studied, namely Argyroxiphium sandwicense and Dubautia menziesii (both Asteraceae), Sophora chrysophylla (Fabaceae), Vaccinium reticulatum (Ericaceae) and Styphelia tameiameiae (Epacridaceae) (Fig. 12.16). Typical freezing tolerance is not fully expressed possibly due to a more recent evolutionary status of these taxa. A combination of the two possible adaptive strategies is given in that a period of supercooling occurs prior to ice nucleation. Four of the five species could tolerate extracellular ice formation to a certain degree. For example, in S. tameiameiae in the laboratory there was considerable supercooling prior to ice formation at - 9.4 °C, and the latter did not cause tissue injury.
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