Broccoli (Brassica oleracea) belongs of the Brassicaceae family. Due to being sensitive to transportation damage and moisture reduction, broccoli has a short storage life. Therefore, the purpose of this study is to investigate the effect of melatonin treatment on chlorophyll content and chlorophyllase enzyme activity after harvesting broccoli during storage. In this study Broccoli was divided into control and treatment groups and factorial experiment was conducted using a randomized completely design with three replications. After 30 minutes immersion in 100 µmol L-1 as treatment and distilled water as control. Then it was kept at a temperature of 4°C for 4 weeks. In this research, the indicators of content of chlorophyll pigments, and chlorophyllase enzyme activity in weeks 0, 1, 2, 3 and 4 were evaluated after storage and with three repetitions. The results indicated that there was a significant difference (p<0.05) in the content of chlorophyll a and b in different weeks of storage between the control and the melatonin-treated groups. The melatonin treatment can increase the content of chlorophyll a, b and total chlorophyll by suppressing the activity of chlorophyllase enzyme. So that, melatonin treatment led to a decrease in chlorophyllase enzyme activity, and this decrease in the fourth week in the melatonin-treated group was about 47.8% less than the control group. In general, post-harvest treatment with melatonin can be effective through increasing the content of chlorophyll pigments and also the effect on the activity of chlorophyllase enzyme on the shelf life of broccoli after post-harvest.
