The change in peel color was established by determining a*
and b* coordinates with the hue value (Cheng et al., 2009) using
a Minolta Chroma Meter CR-400 (Minolta Camera Co. Ltd., Osaka,
Japan). Eight individual banana fruits from each treatment were
used for determination of peel color. Each fruit was measured at
three equidistant points from bottom to top on the fruit skin. Color
was recorded using the CIE L*, a* and b* scale. L denotes the lightness
or darkness, a* indicates green to red color, and b* shows blue
to yellow color. Numerical values of L*, a* and b* were converted
into hue value [h0 = tan−1(b*/a*)].
Chlorophyll fluorescence was determined using a portable
chlorophyll fluorometer (FAM 2100, Walz, Germany) in the Fv/Fm
mode (Yang et al., 2011). Eight individual banana fruits from
each treatment were dark-adapted for at least 30 min prior to
measurements. The chlorophyll fluorescence parameters Fo and
Fm were measured. Fo is the minimal or initial fluorescence
when all PSII reaction centers are open, while Fm is the maximal
fluorescence when all PSII reaction centers are closed and
all non-photochemical quenching processes are at a minimum.
The maximal variable fluorescence (Fv = Fm
−
Fo) and PSII quantum
yield (Fv/Fm) were calculated from the Fo and Fm values. The
fluorometer probe was placed firmly on the banana fruit and a
pulse of 10 mmol m−1 s−1 was applied for 0.8 s. Measurements of
fruit chlorophyll fluorescence were taken on each treatment of six
fruits, at three different locations from bottom to top on the fruit
skin.