The carbohydrate changes were measured dialing the cold storage of rhubarb cultivars which have differing duration of cold requirements for breaking their dormancy. During cold storage starch is broken down in both roots and crowns mainly to sucrose prior to future growth. For these carbohydrate changes to occur there is about one third increase in cold requirement of virus free plants compared with virus infected ones. The carbohydrate changes occurring during cold storage correlated closely with the cold requirement necessary to obtain a high yield when rhubarb roots are forced, so offering a method for determining when roots could successfully be forced. During cold storage an increase in the activity of phosphorylase and sucrosesynthetase in the soluble protein fraction prepared from root tissue was observed. This increase in enzymic activity could account for the breakdown of starch to sucrose during cold storage. Glucose and fructose showed very little change and invertase showed an increase in activity at later stages of cold storage. During forcing a marked decrease in sucrose occurred in the root tissue. This decrease in sucrose was partly due to its conversion into starch in the root tissue at the early stages of forcing and its translocation to the growing region for supporting growth of petioles. The main sugars in the petiole were reducing sugars. Petioles from virus free rhubarb contain more sugars than petioles from virus infected rhubarb. There was a considerable seasonal changes in dry matter and carbohydrate in rhubarb roots when growing in the field. In the spring the reserve carbohydrateswere utilized for supporting the growth of the shoot and in the summer the reserve carbohydrates were restored again.
|Date of Award||1976|