Cold-shock induced wilting and recovery in Brassica campestris L-(cv. Komatsuna) grown in unheated greenhouses

Ln winter cultivation of leaf crops, cold-shock often leads to severe wilti ng as well as freezing injury. Although wilting at low temperature is commo nly observed in many plant species, the mechanism of the response is still unclear. Brassica campestris L. (cv. Komatsuna) is a good test crop for und erstanding the process of wilting and recovery due to its ability to acclim ate to cold conditions. We investigated variations in the stomatal conducta nce and leaf water potential in response to low temperature. The results su ggest that wilting was primarily caused by reduced water-uptake, and the st omatal response to water stress was not affected by lowered temperature. Osmotic potential of cold acclimated plants that had recovered from wilting was lower by 0.6 MPa than in less acclimated plants. The depression in osm otic potential was accounted for an increase in sugars. Sugars are thought to function mainly as cryo-protectants. However, our results suggest that a ccumulation of these solutes is important not only for freezing tolerance b ut also for prevention of cell dehydration under low temperatures.