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Title: Freezing tolerance and the histology of recovering nodes in St. Augustinegrass

item Livingston, David
item KIMBAL, JENNIFER - North Carolina State University
item Tuong, Tan
item CLAURE, TITO - North Carolina State University
item ARELLANO, CONSUELO - North Carolina State University
item MILL-LEWIS, SUSANA - North Carolina State University

Submitted to: International Turfgrass Society Research Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2012
Publication Date: 9/7/2013
Citation: Livingston, D.P., Kimbal, J.A., Tuong, T.D., Claure, T.E., Arellano, C., Mill-Lewis, S.R. 2013. Freezing tolerance and the histology of recovering nodes in St. Augustinegrass. International Turfgrass Society Research Journal. 12:523-530.

Interpretive Summary: St. Augustinegrass is a common lawn grass used in southern states in the US. Its drought and shade tolerance make it a good choice for homeowners and golf courses in many regions. However, it has very low freezing tolerance and is killed in many areas when temperatures remain below zero for extended periods. Breeders and growers need an effective and accurate way to measure freezing tolerance under controlled conditions since winters are so unpredictable. In this study we have identified a few factors that will make selection of freezing tolerant germplasm under controlled conditions more effective. We showed that cold acclimating at 5C for one week was more effective than at a colder temperature and that nodes in the middle of the stolon are more effective at cold acclimation than those at either the apical end or the basal end of the stolon. IN a histological analysis we also identified the location of the hardiest tissue which was meristematic regions on either side of the nodes. A 3D reconstruction of the inside of the node shows considerable vessel plugging at one end of the node. In addition, it appears that the basal end of the node, with more lignin-like cells, was more freezing tolerant than the apical end.

Technical Abstract: St. Augustinegrass [Stenataphrum secundatum (Walt.) Kuntze] is a coarse-textured turfgrass commonly utilized for its excellent shade tolerance. However, inferior cold tolerance in comparison to other warm-season grasses limits its range primarily to the southeastern U. S., The objectives of this study were to evaluate the response of Raleigh and Seville, 2 cultivars at either extremes of freezing tolerance, to different cold-acclimation and freezing temperatures, determine if nodal position has an effect on freezing tolerance, and document changes in specific tissues within the node during recovery from freezing stress. Overall, Raleigh was significantly more freezing tolerant than Seville but Seville appeared to have benefited more from cold-acclimation than Raleigh. Significant differences in survival rates were found in the nodal position of the stolon as well. Nodes in the mid region of the stolon were more freezing tolerant than immature nodes in the apical region and older nodes in the basal region of the stolons. Upon freezing, histological analysis revealed St. Augustinegrass stolon’s xylem vessels were plugged, possibly with phenolic compounds, and the basipetal regions of the nodes received the least structural damage. The observation of new shoots despite severe damage suggests that the most freezing tolerant areas of the plant are the meristematic regions where new shoots and roots originate. Data generated in this study make a significant addition to the understanding of freezing processes and survival in St. Augustinegrass which should aid in the development of methods that are more effective in the evaluation of freezing survival.