Ultrastructural features of chilling injury: injured cells and the early events during chilling of suspension-cultured mung bean cells

The ultrastructure of cells of mung bean (Vigna radiata L. var. Wilczek) in suspension culture was studied during chilling. During such treatment, three kinds of injured cells were observed: swollen cells, cells with broken vacuolar membranes, and cells with shrunken plasma membranes. Swelling was observed from the early stages of chilling, and in most cells during chilling. The other two types of cells were observed at the late stages of chilling. At the early stage of chilling, whorls of rough endoplasmic reticulum that surrounded clear regions of cytoplasm were observed. At the same time, markedly rough vacuolar membranes, plastids and mitochondria with vacuoles, enlargement of Golgi vesicles, and dilation of the ER were seen. These changes preceded the swelling of cells. These ultrastructural features of chilling injury are discussed in terms of biochemical observations. The disruption of the vacuolar membrane and the shrinking of the plasma membrane are discussed in terms of destruction of the cytoskeleton.