Does the life‑history strategy determine the freezing resistance of flowers and leaves of alpine herbaceous species?

Abstract

In high-mountain habitats, summer frost events can have negative consequences for plant fitness. Despite this, most studies have evaluated the consequences of frosts for vegetative structures of perennial plants, and neither for leaves nor for flowers of annual plants. We hypothesize that the degree of freezing resistance of flowers and leaves of a species depends on its life-history strategy (LHS), and is probably the consequence of a trade-off between growth/reproduction and the cost of the freezing resistance. Specifically, flowers and leaves of short-lived annual species should be less freezing resistant than those of perennial plant species. We compared the freezing resistance of flowers and leaves of 10 annual and 12 perennial plant species from the Andes of central Chile using the electrolyte leakage method. Temperature damage for 50% tissue (LT50) of annual species was - 9.6 degrees C in flowers and - 11.9 degrees C in leaves. In perennial species, LT50 was similar in flowers (- 12.3 degrees C) and leaves (- 12.5 degrees C). Despite that, these differences were not significant (except the flowers of annual species), we found remarkable differences between LHS when freezing resistance was analyzed species by species. Like this, 58% and 83% of perennial species resist temperatures <= - 10 degrees C in their flowers and leaves, respectively, compared with only 30% and 40% of annual species. Additionally, in most of the species, the freezing resistance of leaves was greater than that of flowers, with this proportion being greater in annual (58%) than in perennial species (43%). Thus, we concluded that the degree of freezing resistance depends on the LHS, such that annual species, which are less freezing resistant than perennial species, have an infrequent occurrence and a distribution restricted to low elevation in high-mountain habitats.