Effect of 1-methylcyclopropene on senescence and sugar metabolism in harvested broccoli florets

The effect of 1-methylcyclopropene (1-MCP) treatment on superficial color, sugar content and the activities of sugar metabolism enzymes, the expression of sucrose transporters and carbohydrate metabolizing enzymes in broccoli florets were investigated. Broccoli florets treated with 2.5 μL L−1 of 1-methylcyclopropene (1-MCP) inhibited the increase of lightness (L*) value and retarded the decrease in hue angle (H) value and chlorophyll content. This treatment maintained higher levels of sugars comparing with control florets. In general, the activities of sucrose synthase-synthesis direction (SS-S) were enhanced in florets treated with 1-MCP, whereas the activities of sucrose synthase-cleavage direction (SS-C), glucokinase (GK) and UDP-glucose pyrophosphorylase (UGPase) were reduced. In addition, the expression of genes encoding sucrose transporters (BoSUC1 and BoSUC2) and carbohydrate metabolizing enzymes (BoINV1, BoHK1 and BoHK2) was induced upon 1-MCP treatment. These results indicated that 1-MCP can delay senescence of broccoli florets in the present study may be attributed to maintaining higher sugar content through regulation of sugar metabolism.