Agriculture Reference
In-Depth Information
The cause of pre-harvest
peel pitting
is not well known, although cold and dry
winds, low temperature and relative humidity have been suggested as responsible
for pitting. These climatic conditions change the physiological properties of mem-
branes and cuticles and modify the water balance of injured areas.
The breakdown of epidermal cells is the first event of
peel pitting
. The shape
of the injured epidermal and hypodermal cells are responsible for undulating and
depressed appearance of the rind in affected fruit, with no observable disruption of
the cuticle. These depressed areas are devoid of crystalline wax structures and have
crushed epidermal and hypodermic cells with unfolded walls. These cells are either
empty or filled with reduced cytoplasm amount that is located in central position
of the cell.
Some antitranspirants, such as pinolene, a polyterpen film former, replaces the
loss of crystalline waxes and, in this way, can substitute for their action, reducing
the water loss of fruit.
The application of calcium nitrate just before or at fruit colour-break has been
shown to be effective in controlling pre-harvest
peel pitting
of 'Fortune' mandarin.
There are evidence of a relationship between the reduction of
peel pitting
and the
decrease of water permeability associated with the use of calcium nitrate.
Puffing
Puffing
is a physiological disorder characterized by separation between peel and
pulp (Fig.
6.4c
). It is related to the disintegration of the deepest cell layers of the
albedo tissue that gives rise to aerial spaces. The development of these spaces re-
sults in a cracked and low resistant albedo in mature fruits. The symptoms increase
as peel grows just after the pulp has completed its development. This belated peel
growth takes place only in a few mandarin varieties, such as 'Satsuma' mandarin or
'Oroval' clementine mandarin, which are susceptible to
puffing
.
The cause of
puffing
has been related to the water exchange regulation through
the peel. Accordingly, high values of RH together with high temperatures at fruit
colour-break increase the appearance and intensity of
puffing
, particularly after a
period of drought.
The application of 10 mg l
−1
of GA
3
before fruit colour-break reduces the occur-
rence of
puffing
in Satsuma mandarin. The GA
3
treatment prevents the late growth
of the peel and increases the compactness of the albedo. The addition of nitrogen
compounds reinforces the effect of GA
3
. The main internal fruit characteristics are
not modified by such treatments.
Creasing
Creasing
is a physiological disorder of fruits causing cracks in the cell layers of
albedo tissue of peel. It corresponds with depressions on the flavedo that alternate
