Submitted to: International Symposium on Plant Cold Hardiness
Publication Type: Abstract Only
Publication Acceptance Date: 5/30/2004
Publication Date: 7/10/2004
Citation: Livingston, D.P., Tallury, S.P., Premakumar, R., Owens, S., Olien, C.R. 2004. Recovery from freezing: histological and biophysical evidence for differential survival of tissue with oat crowns. International Symposium on Plant Cold Hardiness. p. 45. Interpretive Summary: The Crown is the part of cereal crops that survives during winter. Freeze damage within oat crowns was evaluated by sectioning plants at various stages of recovery after they had been frozen. We confirmed that the upper part of the crown called the apical meristem was the tissue in the crown most tolerant of freezing. The "transition zone", which is below the apical meristem, was killed at a warmer temperature than the apical meristem. Using light microscopy and digital photography we demonstrated survival and growth of the apical meristem when the overall plant was clearly dead. This research will help breeders better understand the processes involved in freezing during the winter and will help them select more winter hardy plants.
Technical Abstract: The survival of cereal crops during winter depends primarily on the ability of tissue in the crown to withstand various stresses encountered during freezing. Freeze-induced damage to specific regions of oat crowns was evaluated by sectioning plants at various stages of recovery after they had been grown and frozen under controlled conditions. Our results confirmed those reported for barley and wheat, that the apical meristem was the tissue in the crown most tolerant of freezing. The "transition zone", which is subjacent to the apical meristem, was killed at a warmer temperature than the apical meristem. Using light microscopy and digital photography we demonstrated survival and growth of the apical meristem when the overall plant was clearly dead. Closer examination revealed that the nuclei of many cells were damaged during freezing and apparently never recovered. A technique was developed to separate the Crown Meristem Complex (CMC) from oat crowns and fractionate it into two regions: the upper portion of the CMC called the apical meristem and the lower portion called the transition zone. Using isothermal calorimetry we determined that in non-hardened plants, 68% of the total water in the apical meristem froze at -2C while 80% of the total water in the transition zone froze. This was in spite of the moisture content being significantly higher in the apical meristem. During cold-hardening the percentage of total water freezing at -2C became lower and lower and after three weeks was 48 and 53% in the apical meristem and the transitional zone, respectively. Research is continuing to determine reasons for the differences between the two tissue regions and to explain how they are related to the differential survival of the two regions of the crown.