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 th e effects of the intensity and duration of soil freezing on root injur y and the survival of white lupin seedlings of different ages under co ntrolled conditions. The extent of root damage depended on both the in tensity of soil freezing and the stage of seedling development (measur ed as the extent of lignification of the central stele of the primary root). Seedlings whose secondary root development was well advanced, a nd 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 kill ed by more intense freezing (5 days at -2 degrees C). The extent of ro ot development and Lignification was correlated with the number of lea f primordia produced at the shoot apex so that the susceptibility to s oil freezing damage could be accurately predicted by a simple physiolo gical/leaf production model.