Spring and summer frost events in high-elevation ecosystems can have strong negative consequences for plant fitness. Despite the above, few studies have investigated this situation in natural communities and most have focused on determining the leaf freezing resistance. Remarkable is the case of reproductive tissues, where little is known about the degree of freezing resistance and less about the underlying mechanism. About this, it is intuitive to think that life history strategy could play a role in the energy destined to protection and therefore in the frost resistance of certain structures within a plant. For example, those short-lived plants, which reproduce once during their life cycle (annual plants), should have a higher energy investment in the protection of reproductive structures than long-lived plants, which reproduce several times (perennial).
In this study, we experimentally investigated the vegetative and reproductive freezing resistance of 10 annual and 16 long-lived perennial herbaceous plant species from an alpine ecosystem in Central Chilean Andes. Specifically, we asked whether vegetative and reproductive frost resistance was similar between species within different life strategies.
Results/Conclusions
Our results revealed significant differences in floral freezing resistance, but not in leaf freezing resistances, between annual and perennial plants. Specifically, and contrary to our hypothesis, perennial plants had a higher floral freezing resistance (⁓ 2 degrees Celsius less) than annual plants. At interspecific level, our results showed that there was no differences between floral and leaf freezing resistance in the 62.5% of perennials and 50% of annual plants studied. For the remaining species, floral tissue was significantly more freezing resistant than leaf tissue in 10 of the 16, and 1 of the 10 perennial and annual species respectively. Conversely, 19% of perennial and 40% of annual plant showed the opposite trend, where leaf tissue was more freezing resistance than floral tissue.
These results show that the degree of vegetative and reproductive freezing resistance is very dependent on the species. The most striking result is that it is not a general pattern that reproductive tissues are more freezing sensitive than vegetative ones, as it has been considered up to now. It is very likely that freezing resistance is not just related to life strategy, but it is a more specific response. This response could be related to life history traits as: flowering timing, flower vs. leaves lifespan, biomass allocation, etc. and/or physiological traits as: freezing resistance strategy (tolerance vs. avoidance) or whole-plant freezing resistance mechanisms.