ETHYLENE IN STORAGE: AN EVALUATION OF THREE INFLUENTIAL FACTORS ON TULIP BULBS' SENSITIVITY TO ETHYLENE DURING POSTHARVEST SHIPPING AND STORAGE
During transport and the subsequent storage of tulip bulbs, inadvertent failure in ventilation and/or high contamination of Fusarium-infected bulbs may expose healthy bulbs to high concentrations of ethylene. Ethylene is known to cause many detrimental effects on forcing quality, including gummosis, increased respiration, flower bud abortion, bulb splitting and poor rooting. In this work, exposure duration and timing as well as the post-stress storage temperatures were evaluated for their potential effects on ethylene sensitivity in bulbs of four tulip cultivars. Degree of damage in sensitive cultivars `Apeldoorn' and `World's Favourite' increased with days at about 10 ppm ethylene starting at 9 and 16 days respectively. This effect strongly depended on timing of ethylene stress, as late treated bulbs showed more severe responses to ethylene treatment than early treated bulbs. Additionally, bulbs that were cooled immediately after ethylene stress, compared with those stored at 17 °C after stress, have significantly higher flowering quality in all attributes measured. This response was also strongly dependent on timing of ethylene stress and cultivar. Implications of the potential cold reversal of ethylene damage as well as effects of ethylene exposure duration and timing of stress on shipping and storage recommendations will be discussed.