Wednesday, 9 November 2005 - 8:30 AM
239-2

Freezing Damage to Wheat at Ear Emergence.

Michael P. Fuller1, Andrew M. Fuller1, Spyridon Kaniouras1, Jack Christopher2, and Troy Fredericks2. (1) School of Biological Sciences, University of Plymouth, Drake Circus, Plymouth, PL4 8AA, United Kingdom, (2) The Leslie Research Institute, Dept of Primary Industry, Toowooba, Queensland, Australia

In Australia and other continental climates wheat is exposed to freezing temperatures during ear emergence and suffers severe frost damage. Convective and radiative freezing experiments were conducted using excised ears and whole plants of a European winter and an Australian spring wheat. Ice nucleation and freezing were observed in some of the experiments using infrared thermal imaging. It was clearly demonstrated that ears of wheat were damaged upon freezing below -5 oC but showed a remarkable ability to supercool and escape damage. Individual culms on a plant froze as independent units during radiation freezing with little or no cross ice-nucleation. In the presence of ice nucleation agents (bacterial solution or water droplets) the likelihood of freezing, and thereby damage, was significantly increased but water was only a weak nucleating agent. Neither winter or spring wheat were capable of demonstrating acclimation at ear emergence supporting the recent published work which indicates that acclimation genes are switched off once vernalization requirement is fulfilled. The results suggest that wheat has an inherent ability to survive mild freezing but freezing-avoidance may be an important strategy to avoid damage below -5 oC.

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