Postharvest treatment of preclimacteric fruit with ethylene often con-
tributes to a faster and more uniform ripening before distribution to the
retailer. The role of ethylene during ripening of nonclimacteric fruit
is still obscure. Ethylene treatment may promote ripening but the lack
of autocatalytic ethylene production means that when moved to an
ethylene-free atmosphere, ripening rate returns to the original level.
Some nonclimacteric fruit resemble vegetables (cucumbers, sweet
pepper and squash) and are harvested and consumed unripe compared
with most other fleshy fruits. Ripening, visualized by incipient de-
greening of greenhouse cucumbers, is regarded as a loss of quality and
renders the fruits unsaleable compared with sweet pepper where a color
change from green to red or yellow is not regarded as a loss of quality.
Postharvest handling of these fruits therefore resembles that of leafy veg-
etables. Accumulation of soluble sugars during ripening and cell-wall
softening, common features of most fleshy fruits, are absent in cucum-
bers and squash. Ripening of cucumbers is in addition to chlorophyll
breakdown accompanied by an accumulation of citric acid in the endo-
carp tissue. The taste of a cucumber thus becomes more acid during the
postharvest period.
Cell-wall structure and composition normally change during senes-
cence of many plant organs. Fruit ripening differs clearly from most veg-
etative plant organs by softening of fruit flesh, which renders the fruit
more palatable. Softening is a result of enzymatic fragmentation of pec-
tic polymers in the middle lamella and hemicelluloses in the cell wall
as well as degradation of starch and loss of turgor. These modifications
reduce cell-to-cell adhesion and the strength of the cell walls, making
the fruit more sensitive to bruising during postharvest handling (Miller,
1992). Control of tomato softening during postharvest storage allows
harvest of vine ripe tomatoes with enhanced flavor. Such control has be-
come an important tool for maintaining tissue integrity and tomato firm-
ness during transport and marketing. Additional strategies include the
introduction of ‘Long life’ cultivars, which are now grown as a winter
crop in the Mediterranean for export to northern Europe as well as ge-
netically manipulated fruits such as the ‘Flavr Savr’ tomato (Kramer and
Redenbaugh, 1994).
Dormancy and Regrowth
Among those vegetables programmed for winter dormancy with sub-
sequent regrowth and sprouting the following year, clear differences in
the biennial behavior are evident. This is probably related to the climatic