Ice nucleation and frost resistance of Pinus canariensis seedlings bearing needles in three different developmental states

Abstract

Frost resistance and ice formation in different developmental states of needles of P. canariensis seedlings were assessed. Regrowth after frost damage was used to determine the overall frost survival capacity. Two distinct freezing exotherms (E1, E2) were registered. E1 was between -1.7 and -2.0°C. Initial frost damage (LT10) was 1.5-2.7°C below E1. E2 was between -5.6 and -6.0°C, and either corresponded with LT50 or occurred in between LT10 and LT50. Current year needles were less frost resistant than 1-year-old needles. The overall recuperation capacity of seedlings revealed that frost survival may be underestimated when only needle damage is assessed. Freezing of seedlings with or without roots had no effect on the frost resistance of needles but recuperation capacity was significantly affected. Seedlings survived -10°C during summer indicating that they withstand the lowest naturally occurring frosts in Tenerife. © INRA, EDP Sciences, 2007.