Ethylene production and its effect on storage respiration rate in wounded and unwounded sugarbeet roots

Authors: Fugate, Karen; Suttle, Jeffrey

Submitted to: American Society of Sugarbeet Technologists
Publication Type: Proceedings
Publication Acceptance Date: 3/12/2007
Publication Date: 8/1/2007
Citation: Klotz, K.L., Suttle, J.C. 2007. Ethylene production and its effect on storage respiration rate in wounded and unwounded sugarbeet roots. In: Proceeding of the 34th Biennial Meeting of the American Society of Sugarbeet Technologists, Agriculture, February 28-March 3, 2007, Salt Lake City, Utah. p.138-142.

Interpretive Summary: Ethylene is a natural plant hormone that induces respiration in most plant tissues and organs. To understand the extent to which this compound affects the respiration rate of sugarbeet roots in storage, a series of experiments were conducted to measure ethylene production by wounded and unwounded roots and determine ethylene’s effect on root respiration rate. Low levels (0.17 nmol kg-1 h-1) of ethylene were produced by healthy, uninjuried roots. Severe injury caused ethylene production to increase by approximately five-fold. Concurrent with the increase in ethylene after root injury, respiration rate increased 1.5 to two-fold. Experiments with ethylene synthesis and response inhibitors demonstrated that the increase in respiration due to injury was partly a response to elevated ethylene production. Research also demonstrated the ability of exogenous ethylene to induce respiration in sugarbeet roots. Healthy roots may be exposed to exogenous ethylene by their proximity to severely injured roots or ethylene-producing pathogens in a storage pile.

Technical Abstract: Ethylene is produced by all seed plants and stimulates respiration in most plant tissues and organs. To understand how this plant hormone may affect postharvest sugarbeet root respiration, a series of experiments were conducted to determine (1) the rate of ethylene production in wounded and unwounded roots, (2) the effect of exogenous ethylene on root respiration rate, and (3) the effect of ethylene synthesis and response inhibitors on the storage respiration rate of wounded and unwounded roots. All experiments were conducted at 10oC. For the wound treatment, roots were severely bruised and abraded by tumbling in a tare lab beet washer for 30 min. This injury caused a 1.5 to two-fold increase in respiration rate in the 72 to 96 h after the injury. Ethylene production by unwounded roots averaged 0.17 nmol kg-1 h-1. In wounded roots, ethylene production averaged 0.79 nmol kg-1 h-1 during the first four days after injury, a five-fold increase over unwound roots. Treatment with exogenous ethylene at concentrations of 0.02, 0.1, 1.4 and 14 ppm increased respiration in a dose-dependent manner with respiratory increases ranging from 60% at 0.02 ppm ethylene to 130% at 14 ppm ethylene. At 0.02 and 0.1 ppm ethylene, the increase in respiration was transient, lasting only 48 h. At 1.4 and 14 ppm ethylene, the increase in respiration persisted for at least four days. The ethylene response inhibitor, silver thiosulfate, and the ethylene synthesis inhibitor, aminoethoxyvinylglycine, reduced wound-induced respiration rate by approximately 60%, but did not significantly lower respiration rate in unwounded roots. No consistent effect on sugarbeet root respiration was achieved with the ethylene response inhibitor, 1-methylcyclopropene. These results demonstrate that unwounded sugarbeet roots produce low levels of ethylene, that ethylene synthesis is induced by injury, and that ethylene has a role in the increase in respiration that occurs following injury.