Cold temperature delays wound healing in postharvest sugarbeet roots

Authors: Fugate, Karen; RIBEIRO, WELLINGTON - Universidade Federal De Vicosa; Lulai, Edward; DECKARD, EDWARD - North Dakota State University; FINGER, FERNANDO - Universidade Federal De Vicosa

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2016
Publication Date: 4/14/2016
Citation: Fugate, K.K., Ribeiro, W.S., Lulai, E.C., Deckard, E.L., Finger, F.L. 2016. Cold temperature delays wound healing in postharvest sugarbeet roots. Frontiers in Plant Science. 7:499. doi: 10.3389/fpls.2016.00499.

Interpretive Summary: Storage temperature affects the rate and extent of wound-healing in a number of root and tuber crops. The effect of storage temperature on wound-healing in sugarbeet roots, however, is largely unknown. Wound-healing of sugarbeet roots was investigated using surface-abraded roots stored at 43 and 54 °F for 28 d. Surface abrasions are common injuries of stored roots, and the storage temperatures used are typical of freshly harvested or rapidly cooled roots. At 54 °F, wound healing was evident within 14 d after the injury and wounded roots lost weight at a rate similar to unwounded controls. At 43 °F, however, no evidence of wound healing was apparent even after 28 d storage, and wounded roots lost 44% more weight than controls in the 28 d after injury. Melanin, lignin, and suberin seal off wounded surfaces in plants. Formation of these three compounds occurred more rapidly at 54 °F than at 43 °F, and a continuous layer of lignified and suberized cells developed at 54 °F, but not at 43 °F. Examination of enzyme activities involved in melanin, lignin, and suberin formation indicated that differences in melanin formation at 43 and 54 °F were related to differences in polyphenol oxidase activity. Wound-induced respiration was initially greater at 54 °F than at 43 °F. However, with continued storage, respiration rate of wounded roots declined more rapidly at 54 °F, and over 28 d, the increase in respiration due to injury was 52% greater in roots stored at 43 °F than in roots stored at 54 °F. The data indicate that storage at 43 °F severely slowed and impaired wound-healing of surface-abraded sugarbeet roots relative to roots stored at 54 °F and suggest that postharvest losses may be accelerated if freshly harvested roots are cooled too quickly.

Technical Abstract: Storage temperature affects the rate and extent of wound-healing in a number of root and tuber crops. The effect of storage temperature on wound-healing in sugarbeet (Beta vulgaris L.) roots, however, is largely unknown. Wound-healing of sugarbeet roots was investigated using surface-abraded roots stored at 6 and 12 °C for 28 d. Surface abrasions are common injuries of stored roots, and the storage temperatures used are typical of freshly harvested or rapidly cooled roots. Transpiration rate from the wounded surface and root weight loss were used to quantify wound healing. At 12 °C, transpiration rate from the wounded surface declined within 14 d and wounded roots lost weight at a rate similar to unwounded controls. At 6 °C, however, transpiration rate from the wounded surface did not decline even after 28 d storage, and wounded roots lost 44% more weight than controls after 28 d storage. Melanin formation, lignification, and suberization occurred more rapidly at 12 °C than at 6 °C, and a continuous layer of lignified and suberized cells developed at 12 °C, but not at 6 °C. Examination of enzyme activities involved in melanin, lignin, and suberin formation indicated that differences in melanin formation at 6 and 12 °C were related to differences in polyphenol oxidase activity, although no relationships between suberin or lignin formation and phenylalanine ammonia lyase or peroxidase activity were evident. Wound-induced respiration was initially greater at 12 °C than at 6 °C. However, with continued storage, respiration rate of wounded roots declined more rapidly at 12 °C, and over 28 d, the increase in respiration due to injury was 52% greater in roots stored at 6 °C than in roots stored at 12 °C. The data indicate that storage at 6 °C severely slowed and impaired wound-healing of surface-abraded sugarbeet roots relative to roots stored at 12 °C and suggest that postharvest losses may be accelerated if freshly harvested roots are cooled too quickly.