SURVIVAL OF FROZEN TISSUE IN WINTER OAT CROWNS

Authors: Livingston, David; TALLURY, SHYAMALRAU - NORTH CAROLINA STATE UNIV

Submitted to: American Oat Workers Conference Proceedings
Publication Type: Other
Publication Acceptance Date: 6/15/2006
Publication Date: 7/24/2006
Citation: Livingston, D.P., Tallury, S. 2006. Survival of frozen tissue in winter oat crowns. American Oat Workers Conference Proceedings. p. 19.

Interpretive Summary: There is a below ground portion of the stem of winter cereals, such as rye, wheat, barley and oats, that over winters and must survive if the plant is to re-grow in the spring; this part of the plant is called the crown. The crown is a complex region of tissue that is made up of numerous types of cells and can be organized into 2 parts that differ in their ability to survive freezing. The upper part, called the apical region, is very tender before plants are cold acclimated but after cold acclimation becomes the most freezing tolerant region of the crown. The lower part of the crown called the crown core is the least hardy tissue of the crown after cold acclimation. Using light microscopy and digital photography we have documented changes that occur in these two regions of the crown after freezing. We have also been able to separate the two regions and analyze them separately for various biochemical properties that may be related to their differences in survival. These findings should help physiologists understand why freezing tolerance is so complex in winter cereals and will help breeders know which traits are important to breed in order to improve winter hardiness.

Technical Abstract: The part of oat that over winters, known as the crown, is a complex organ composed of numerous cell types distributed in seemingly random patterns. Winter oats, like other winter cereals, survive freeze conditions during winter by various protective mechanisms within this vital tissue. The lower part of the crown is composed of xylem and phloem vessels that are flanked by numerous large parenchyma cells. The center of the lower crown, called the crown core, is the tissue that provides continuity from the roots to the upper part of the crown called the apical meristem. This apical region is the tissue that is most susceptible to freezing in plants that have not been cold acclimated. During cold acclimation the apical region rapidly becomes more freezing tolerant than the rest of the crown and after 3 weeks of cold acclimation is the most freezing tolerant tissue in the crown. Paraffin embedded sections that were triple stained were photographed to illustrate the recovery of various tissues and cell types within the crown after freezing. The crown was then fractionated into 2 regions and analyzed to quantify biochemical differences between the tissues. Percent moisture, the percentage of water freezing, carbohydrate concentrations and invertase activities differed significantly between the 2 regions. These differences will be discussed in relation to the survival of the tissues. In addition, the survival of specific tissue within oat crowns was compared to more winter hardy cereals (barley, wheat and rye). Differences in tissue survival between species will be the basis of a metabolomics study to determine why oats are the most susceptible winter cereal to freezing conditions.