Summer freezing resistance of high-elevation plant species changes with ontogeny

In high-elevation habitats, an apparent trade-off between high growth-rates and freezing resistance has led some authors to assume that seedlings are less freezing resistant than adults. However, because seedlings are exposed to lower and longer freezing events near the ground, they could be more freezing-resistant than adults. As freezing resistance is related to plant height, ontogenetic changes in the intensity of freezing resistance and the mechanism involved should differ between seedlings and adults of tall vs. short plants, with those changes being greater for tall plants. We evaluated differences between seedlings and adult plants in the ability to resist freezing temperatures in 13 high-Andean species from central Chile. In a field laboratory, we determined the low temperature damage, ice nucleation temperature and freezing resistance mechanisms in their leaves. Seedlings were on average 3.4 K less freezing resistant than adults with greater differences found for tall plant species. Six species changed their freezing resistance mechanism with ontogeny, including short and tall plants, although changes were greater for tall plant species. Ontogenetic changes in the freezing resistance of high-Andean species seem to be more related to a trade-off between plant-growth and stress resistance than to differences in thermal microhabitats between seedlings and adults.

► We evaluated ontogenetic changes in the freezing resistance of 13 high-Andean species.
► We determined the magnitude and mechanisms of freezing resistance in their leaves.
► Seedlings were 4 K less freezing resistant than adults, particularly for tall plants.
► Six species changed their mechanism with ontogeny, including short and tall plants.
► Ontogenetic changes are related to a trade-off between growth and resistance to stress.