Abstract:

The relationship between chlorophyll fluorescence parameters and the development of superficial scald in Granny
Smith apples was studied during postharvest storage at cold (0 ± 1) ℃ or ambient (22 ℃) temperature. Minimal fluorescence (Fo),
maximal fluorescence (Fm), variable fluorescence (Fv) and photochemical efficiency (Fv/Fm) were measured during storage periods.
The results showed that Fo, Fm and Fv/Fm declined clearly in control fruits over days, and 1-methylcyclopropene (1-MCP) treatment
had an effect on Fo and Fv/Fm, both of which displayed relatively gentle changes during the first 60 d of storage, and declined
rapidly from the 90th d onwards, while no significant effect on Fm was observed. Low-oxygen treatment had no obvious effect on
Fo or Fm, but resulted in a continuous decrease in Fv/Fm, which at a level less than 0.7 indicated the appearance of brown spots on
the fruit surface. Thus, we inferred that superficial scald occurred at about 90 d postharvest and could be significantly prevented
from occurring by 1-MCP and low-oxygen treatment. Postharvest storage at ambient temperature accelerated the rate of change
in fluorescence parameters in control and 1-MCP treatment groups, and Fv/Fm declined with increasing storage time, which was
significantly negatively correlated with the incidence of superficial scald.

Key words: apple fruit, superficial scald, chlorophyll fluorescence parameters