Sodium nitroprusside reduces chilling injury in hami melons by regulating postharvest proline metabolism and energy metabolism

This experiment examined the effects of sodium nitroprusside (SNP; 1.0 mmol/L) versus a control (0 mmol/L) on proline and energy metabolism in cantaloupe during low-temperature storage.As storage time increased, SNP treatment during the late storage period (28–42 d) reduced the chilling injury index and rate in Hami melon fruits. SNP increased free proline content, significantly raised P5CS and OAT activities ( p < 0.05), and inhibited ProDH activity and production ( p < 0.05). It delayed the decline of ATP and ADP and significantly increased H⁺-ATPase activity ( p < 0.05). During mid-storage (21–35 d), SNP slowed Ca²⁺-ATPase activity decline ( p < 0.05), maintained higher EC levels, inhibited AMP content, increased SDH activity, and promoted expression of CmP5CS, CmOAT, CmH⁺-ATPase, CmCa²⁺-ATPase, CmSDH , and CmCCO genes ( p < 0.05). Overall, SNP treatment enhances Hami melon cold resistance by regulating osmoregulatory substances and energy metabolism, providing a theoreticalbasis for controlling chilling injury in Hami melon.