Agriculture Reference
In-Depth Information
summarized relevant interactions in terms of three factors in addition to
light controlling red skin colour development. First, temperatures must be
high enough, but not too high, and of sufficient duration in daylight hours to
catalyse anthocyanin biosynthesis. Skin temperatures below
◦
C or above
◦
C are disadvantageous: under sunny conditions they may be much higher
than air temperatures. Secondly, colour development varies with the stage of
maturity. Once the climacteric phase is entered chlorophyll is degraded and
anthocyanin is produced at a much lower rate. Thirdly, a period at cold tem-
peratures stimulates anthocyanin production. A series of a few nights with
temperatures in the range
◦
-
◦
C followed by warm sunny days promotes
red colour development.
Creasy (
◦
C) inhibited an-
thocyanin formation in 'McIntosh' apples even when the nights were cool.
Faragher (
) found that high daytime temperatures (
.
) found that the optimum temperature for anthocyanin forma-
tion in unripe 'Jonathan' apples was
◦
C.
At higher temperatures anthocyanin formation was much lower. Tan (
◦
C, and in ripe apples was
-
)
◦
C
found that whole apples of 'Red Spy' receiving alternating periods at
◦
C in constant light or with darkness in the low-temperature period
accumulated much more anthocyanin than apples receiving a constant
and
◦
C.
Some cultivars, e.g. 'McIntosh', 'Cortland' and 'Northern Spy', appear
to be especially dependent on low temperatures for anthocyanin synthesis
and 'Richared Delicious', 'Idared' and 'Spartan' tolerant of high temperature
(Proctor,
). 'Delicious' and 'Fuji' have higher temperature optima than
'Gala' and 'Braeburn' (Curry,
). The highly coloured 'Scarlet Spur' sport
of 'Delicious' has a similar rate of anthocyanin production to 'Oregon Spur'
up to
◦
C.
Cooling apples by over-tree water sprinkling can substantially improve fruit
colour. Unrath (
◦
C but much higher rates at higher temperatures, even up to
) found that the amount of solid-red surface of 'Red
Delicious' apples was doubled by this treatment.
In Japan fruits have traditionally been enclosed in paper bags from about one
month after full bloom until shortly before harvest (Fukuda,
; Proctor and
Lougheed,
). This practice, which protects from pest injury and disease,
now has the main objective of producing smooth-skinned, vividly pink or red
fruits.
For most cultivars bagging greatly reduces skin chlorophyll contents, which
do not increase subsequently unless the fruits are exposed for
days
prior to harvest. This lack of chlorophyll results in a unique pink or red colour
being induced by anthocyanin (Proctor and Lougheed,
-
). Anthocyanin
production occurs within
days of re-exposure to light. In most cultivars
the previously bagged fruits produce more anthocyanin than unbagged ones.
-
