Combined modified atmosphere package and melatonin treatments delay the senescence of bitter bamboo shoots by inhibiting the cell wall changes after harvest

The tender bamboo shoots are prone to senescence with rapid increase of hardness after harvest. In this study, the combined treatments of modified atmosphere package and melatonin were applied to enhance the inhibition of cell wall metabolisms in delaying senescence of tender bitter bamboo shoots. This combined treatment could obviously suppress the increase of CO₂ and decrease of O₂ in packages, and the changes in level of firmness, total pectin, cellulose, and lignin of bitter bamboo shoots. The enzymes for cell wall polysaccharides such as polygalacturonase (PG), cellulase, and pectinase, and enzymes for lignin accumulation including phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), peroxidase (POD), and laccase were apparently modified. Additionally, the biosynthesis genes of PaPAL3/4, PaCAD, Pa4CL, PaC4H, PaCCOAOMT, PaCOMT, PaSND2, and PaCESA1 in related to the lignin formation, as well as PaKNAT7, PaMYB20, PaMYB63 and PaMYB85 as the regulated transcription factors were obviously regulated. These findings indicate that the combined treatments could effectively mitigate the cell wall polysaccharide and lignin content, thereby extending shelf-life for bitter bamboo shoots after harvest.