Submitted to: Postharvest Biology and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/10/2004
Publication Date: 8/15/2004
Citation: Lulai, E.C., Suttle, J.C. 2004. The involvement of ethylene in wound-induced suberization of potato tuber (Solanum tuberosum l.): a critical assessment. Postharvest Biology and Technology. 34(1)105-112. Interpretive Summary: Potato tubers that are cut for seed and tubers that are skinned, nicked and bruised during harvest and handling operations must rapidly wound-heal to avoid costly disease and blemish problems. Rapid wound-induced suberization of these cuts and damaged areas provides a protective barrier that is similar to that provided by the healthy intact skin of the potato tuber. Despite the costly losses associated with slow or inadequate suberization, the plant hormones controlling this process have not been determined. The plant hormone ethylene is known to be associated with various types of plant stress including wounding. However, the involvement of ethylene in the critical process of wound-induced suberization has not been determined. We used various inhibitors of ethylene biosynthesis and action to determine if ethylene was required for wound-induced suberization. Our results showed that tuber wounding resulted in the induction of ethylene biosynthesis. However, addition of ethylene to the tuber storage environment before wounding and during wound-healing had no effect on the accumulation of suberin. Our research showed that neither inhibition of ethylene biosynthesis, or ethylene action effected the accumulation of suberin during the early or later periods of suberization. These results are of great scientific importance in characterizing the physiology and regulation of suberization because they show that wound-induced ethylene formation is not directly involved in wound-induced suberization. The results are of equally great practical importance because they show that new technologies used to commercially control ethylene action in plant food stuffs will not adversely affect suberization.
Technical Abstract: The determination of hormonal requirements for wound-induced suberization is important in developing new approaches and future postharvest technologies to control various wound related disease and defect problems in potato tuber (Solanum tuberosum L.). Although the hormone ethylene has been shown to be involved in various kinds of plant stress, including that of wound response, its role in suberization had not been determined. The role of ethylene in wound-induced suberization of potato tuber was examined over a 9 d wound-healing period using a variety of ethylene biosynthesis and action inhibitors. Ethylene evolution was stimulated by wounding and reached a maximum 2 to 3 d after tuber wounding, and then gradually declined. The competitive inhibitor of ethylene action, 2,5-norbornadiene, had no effect on the wound-induce accumulation of suberin polyphenolics. Similarly, the ethylene antagonist 1-methylcyclopropene had no apparent effect on wound-induced accumulation of suberin polyphenolics or on the accumulation of suberin polyaliphatics. Treatment of tubers with ethylene, applied either before or after wounding, had no effect on the induction or accumulation of either suberin biopolymer. Treatment with the ethylene biosynthesis inhibitor, aminoethoxyvinylglycine, inhibited wound-induced ethylene production, but did not affect wound-induced suberization. Collectively, these results indicate that although increased ethylene evolution is part of the tuber wound response, ethylene is not required for wound-induced suberization of the closing layer (suberization of existing cells at the wound surface) during the first two to four days of wound-healing or subsequent suberization of phellem cells (between four to nine days) created by the wound-induced formation of the phellogen. These results are of great importance in determining the mechanisms regulating suberization and in assuring that wound-induced suberization is not inhibited with the application of new technologies that effectively control various ethylene mediated processes in vegetables and fruits.