The effect of soil freezing on the survival of winter-sown white lupins (Lupinus albus L.)

Specially constructed soil-freezing growth boxes were used to study the effects of the intensity and duration of soil freezing on root injury and the survival of white lupin seedlings of different ages under controlled conditions. The extent of root damage depended on both the intensity of soil freezing and the stage of seedling development (measured as the extent of lignification of the central stele of the primary root). Seedlings whose secondary root development was well advanced, and in which the endodermis was completely Lignified, survived intense soil freezing intact. Young seedlings with weakly lignified roots were damaged by moderate soil freezing (> 5 days at -1 degrees C) and killed by more intense freezing (5 days at -2 degrees C). The extent of root development and Lignification was correlated with the number of leaf primordia produced at the shoot apex so that the susceptibility to soil freezing damage could be accurately predicted by a simple physiological/leaf production model.