Submitted to: Cryobiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2005
Publication Date: 3/10/2006
Citation: Livingston, D.P., Premakumar, R., Tallury, S.P. 2006. Carborhydrate partitioning in crown tissue of oat and rye during cold acclimation and freezing. Cryobiology 52:200-208. Interpretive Summary: Carbohydrates such as fructan (similar to starch), sucrose (table sugar), glucose and fructose are important as protective compounds to help plants withstand stresses caused by freezing temperatures during winter. However, the mode of action has always been somewhat controversial. We wanted to see if the reason for the controversy was related to differences in carbohydrates within the over wintering organ, the crown. We grew 2 oat cultivars (non winter hardy species) and rye (winter hardy species) and then separated the tissues of the crown into 2 parts: we called the upper part the "apical region" and the lower part, the "lower crown". We found that during a period of cold acclimation carbohydrates in the apical region and lower crown accumulated to different extents. The extent of fructan accumulation was related to the hardiness of the apical region and may help explain how fructan can help plants make it through the winter.
Technical Abstract: Carbohydrates have long been recognized as important in freezing tolerance of plants but the association between these two factors is often ambiguous. To help clarify the relationship, the allocation of carbohydrates during cold acclimation between specific tissues within the over wintering organ (crown) of winter cereals was measured. A winter-hardy and non winter-hardy oat, and a rye cultivar were grown and frozen under controlled conditions. Crown tissue was fractionated into an upper portion, called the apical region, and a lower portion, called the lower crown. These tissues were ground in liquid N, and extracted with water. Extracts were analyzed by HPLC for the predominant sugars, sucrose, glucose, fructose and for fructan size classes up to DP5. After 3 weeks of cold acclimation at 3C, carbohydrates accounted for approximately 40% of the dry weight of oats and 60% of the dry weight of rye. The crown core was generally 10% lower in total carbohydrates than the apical region. During a mild freeze, various carbohydrates were allocated differently between specific tissues in the three genotypes. When frozen, fructan generally decreased to a greater extent in the crown core than in the apical region but sugars increased more in the apical region than in the crown core. Results suggest that to understand how carbohydrates relate to freezing tolerance, regions of the crown that endure freezing stress differently should be compared.