Thermal buffering in Afro-alpine plants due to nucleating agent-induced water freezing

Abstract

Plants in the alpine zone of Mount Kenya are exposed throughout the year to environmental temperatures varying from about −10 to +10°C (ref. 1). In contrast to plants in Arctic and temperate regions, which are in a state of suspended growth during the cold season, these plants have to combine growth with tolerance to low environmental temperatures. It has been suggested that flowers of the Afro-alpine plant Lobelia telekii gain thermal protection from the long, thin bracts which hang down at the outside of the inflorescence, and which seem to lower the radiative heat loss of the plants at night¹. We report here that vital tissues of L. telekii are also protected by the heat of fusion of water, which is present in the central part of the inflorescence, and that freezing of this water is ensured by the presence of nucleating agents, which induce freezing at a few degrees below zero.