Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/1995
Publication Date: N/A
Citation: Interpretive Summary: It is known that growing cereal plants such as rye, wheat, barley and oats at temperatures just above freezing (cold hardening) will make them more resistant to winter conditions. However, little is known about additional hardening at temperatures just below freezing, called the second phase of hardening (2PH). In this study rye, wheat, barley and oats were grown under controlled conditions and test frozen after exposing them to the 2PH at -3 degrees C for up to 7 days. All cultivars benefited significantly from the 2PH. One cultivar hardened above freezing had a survival of 3%; when the same cultivar was given a 7 day period of hardening at -3 degrees C its survival increased to 100%. This additional hardening may be the result of carbohydrate shifts that occurred during the second phase of hardening. Different oat cultivars benefited to a different extent from the 2PH. This suggests that not all cultivars have the ability to harden during the 2PH and that it may be possible to transfer the ability and increase winter hardiness.
Technical Abstract: Cold-hardening plants at above freezing temperatures significantly contributes to their overall winter hardiness. Little research has been conducted however, on hardening at temperatures below freezing, before freezing injury results. Barley, and oats were grown and hardened under controlled conditions and freeze tested after being held at -3 degrees C from one to 7 days. The biggest change in LT-50 after the second phase of hardening (2PH)) was a reduction of 7 degrees C, in the winter hardy oat cultivar, Wintok. In addition, after 2PH all 15 fructan isomers of degree of polymerization 3 (DP3) to DP5 in oat were lower while the sugars fructose and sucrose were higher. All carbohydrate changes except that of one DP5 isomer and of Fructan DP>6 were significantly correlated with survival of plants after 2PH.