Effect of maleic hydrazide on respiratory parameters of stored onion bulbs (Allium cepa L.)

Abstract

The respiration rate (RR) (CO2 production), activation energy (Ea) and Q10 of maleic hydrazide-treated onion bulbs (Allium cepa, cv. Rouge Amposta) at 20.10-6 mol.L-1 (MH1) and 45.10-6 mol.L-1 (MH2) were measured at 4, 10 and 20°C. Immediately after treatment, the Q10 of MH-treated and control bulbs were not significantly different. After 8 weeks of storage, Q 10 of control and both MH-treated bulbs increased and ranged from 2.34 and 2.89. Respiration rate of onions increased during storage, and after 24 weeks, RR values of control, MH1 and MH2 were 0.43, 0.32 and 0.26 mmol CO2.kg-1.h-1 at 20°C respectively; and 0.26, 0.20 and 0.17 mmol CO2.kg-1.h-1 at 10°C respectively. At 4°C, no significant difference was observed between control and MH-treated bulbs. After 24 weeks, sprouting of the control and MH1 and MH2-treated bulbs was 75%, 38% and 33% at 20°C respectively, and 50%, 22% and 17% at 10°C respectively. At 4°C, the sprouting level of control bulbs did not exceed 7% and was 5% for MH-treated bulbs. No difference was observed in rotting of control and MH-treated bulbs, and the low rotting observed at 4°C could be attributed to low temperature rather than maleic hydrazide treatment.