Low temperature affects pattern of leaf growth and structure of cell wallsin winter oilseed rape (Brassica napus L., var. oliefera L.)

Three-week acclimation of winter oilseed rape (Brassica napus L. var. oleif era L.) plants in the cold (2 degrees C) resulted in a modified pattern of leaf cell enlargement, indicated by the increased thickness of young leaf b lades and modified dimensions of mesophyll cells, as compared with non-accl imated tissues grown at 20/15 degrees C (day/night). The thickness of leaf cell walls also increased markedly during cold acclimation but it decreased in response to a transient freezing event (5 degrees C for 18 h followed b y 6 or 24 h at 2 degrees C, in the dark). Cell walls of the upper (adaxial) epidermis were most affected. Their ultrastructure was modified by cold an d freezing treatments in different ways, as revealed by electron microscopy . Possible reasons for the cold- and freezing-induced modifications in the leaf and cell wall morphology and their role in plant acclimation to low te mperature conditions are discussed. (C) 1999 Annals of Botany Company.