Chilling root temperature causes rapid ultrastructural changes in cortical cells of cucumber (Cucumis sativus L.) root tips.

Examination of root tips from cucumber (Cucumis sativus L.) seedlings grown at 8 degrees C for varying periods ranging from 15 min to 96 h, showed marked changes in the ultrastructure of cortical cells within only 15 min of exposure. Greater parts of the cortex were affected with longer periods of exposure, but the sequence of morphological changes in cell components was similar to that found for the roots exposed for 15 min. The effect of chilling injury included alterations in cell walls, nuclei, ER, mitochondria, plastids, and ribosomes. The extent of alterations varied greatly among cells, moderate to severe alterations to cell components being observable among adjoining cells. The measurements of root pressure using the root pressure probe showed a sudden, steep drop in the root pressure in response to lowering of the temperature of the bathing solution from 25 degrees C to 8 degrees C. These observations are discussed in the light of the information available on the ultrastructural and biochemical characteristics of the effect of cold exposure in chilling-sensitive plants.