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Title: FREEZING IN NON-ACCLIMATED OATS: A COMPARISON OF THERMAL RESPONSE AND HISTOLOGY OF RECOVERING CROWNS IN GRADUAL AND RAPIDLY FROZEN PLANTS.

Author
item Livingston, David
item TALLURY, SHYAMAL - NORTH CAROLINA STATE UNIV

Submitted to: Thermochimica Acta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2009
Publication Date: 3/25/2009
Citation: Livingston, D.P., Tallury, S.P. 2009. FREEZING IN NON-ACCLIMATED OATS: A COMPARISON OF THERMAL RESPONSE AND HISTOLOGY OF RECOVERING CROWNS IN GRADUAL AND RAPIDLY FROZEN PLANTS.. Thermochimica Acta. 481:20-27.

Interpretive Summary: There are many tissues inside crop plants that under freezing conditions will be damaged more than other tissues. To fully understand how crop plants should be improved by genetic manipulation, scientists need to understand which specific tissues should be modified. We compared the different tissues of oat plants that were frozen suddenly to the same tissues of plants that were frozen slowly. In the suddenly frozen plants the part of the plant that will become the flower (apical meristem) was killed and the tissues just below this were apparently undamaged. In plants that were slowly frozen, the apical meristem was not damaged but the tissue just below it appeared to be infected by bacteria. This means that the plant adapted to ice within its tissues in a different manner depending on whether it was frozen quickly or slowly. Improving the ability of crop plants to withstand microbial infiltration may be a means to improve the over all winter hardiness of plants.

Technical Abstract: Freezing in winter cereals is a complex phenomenon that can affect various plant tissues differently. To better understand how freezing affects specific tissue in the over wintering organ (crown) of winter cereal crops, non acclimated oats were frozen to -3°C over an extended period and tissue damage during recovery was compared to plants that had been supercooled to -3°C and then frozen suddenly. When plants were suddenly frozen the apical meristem was completely killed and plant re-growth was limited. In contrast, the apical region of plants that were slowly frozen survived but extensive vessel plugging, presumably from microbial proliferation, was noted. The percentage of total water frozen, (calorimetrically determined) was the same whether crowns were frozen suddenly or gradually despite the tissues being effected differently. This suggests that chemical equilibrium was attained within the crown by different means and suggests that the apical region was killed by intracellular freezing in the sudden freeze and the crown core was damaged by another process which allowed microbial proliferation within the crown core.