POST-HEAT STRESS RESPIRATION PATTERN OF TULIP BULBS IN STORAGE

Abstract

Dutch-grown tulip bulbs are shipped around the world via ocean freight. Normal transport temperatures are 17 to 20°C, but bulbs can be improperly subjected to high temperature stress due to equipment failure or mishandling. To understand effects of heat stress on internal metabolism of tulip bulbs, we determined the responses to heat treatment of a heat sensitive cultivar (‘Apeldoorn’) and a heat-resistant cultivar (‘Sevilla’). In addition, we tested the hypothesis that heat-induced injuries are related to endogenous ethylene production by treating bulbs with an inhibitor of ethylene perception, 1-methylcyclopropene (1-MCP), prior to heat treatment. Bulbs, either untreated or treated with 1-MCP, were exposed to 35°C for 1 to 7d, and then respirations rates at 17°C were assessed daily. For non-heated bulbs, respiration rates of the heat-resistant cultivar ‘Sevilla’ were much higher than ‘Apeldoorn’. For heated bulbs, respiration rates generally increased as the length of heat stress increased, and patterns of change were similar for both cultivars. Highest rates of respiration over time were found at 2 or 3 days after removal from heat. Effects of 1-MCP were significant, but depended on the stress level.