Hormone Metabolism of Five Bermudagrass Varieties During Cold Acclimation and Deacclimation.

The extent of cultivar metabolic responses to cold acclimation (CA) and deacclimation (DA) are most likely related to freezing tolerance and rate of spring green up in bermudagrass (Cynodon spp.), but the underlying mechanisms are not well documented. This study was conducted to characterize cytokinin (t-zeatin riboside) and abscisic acid (ABA) changes during CA and DA in one ecotype (‘GA ecotype’) and four cultivars (‘Tifway’, ‘Patriot’, ‘Riviera’, and ‘Princess-77’).  Bermudagrasses were subjected to CA (8/4 ºC; day/night) for four weeks, and then to a series of DA temperature regimes ranging from 10/5 ºC (day/night) to 26/14 ºC for 12 weeks. The results showed that stolon cytokinin content declined and ABA increased during CA.  Patriot and Riviera had higher levels of ABA content relative to Princess-77, Tifway, and GA as measured at the end of CA. During DA, cytokinin increased as temperature changed from 23/8 to 26/14 ºC, while ABA declined gradually as temperature changed from 8/4 to 21/7 ºC.  Patriot, GA, and Tifway had greater turf quality and higher level of cytokinin in stolon tissues relative to Riviera and Princess-77 during DA.  The results suggest that higher cytokinin during DA may be associated with quicker spring green up in bermudagrass.