New Zealand Journal of Crop and Horticultural Science
abstracts
Plastid ultrastructure, chlorophyll contents, and colour expression during
ripening of Cavendish banana (Musa acuminata ‘Williams’) at 18°C
and 27°C
Phebe Ding1
S. H. Ahmad1
Abd. R. Abd. Razak1
N. Saari2
M. T. M. Mohamed1
1 Department of Crop Science
2 Department of Food Science
Universiti Putra Malaysia
43400 UPM Serdang, Selangor, Malaysia
Abstract When Cavendish banana (Musa acuminata ‘Williams’)
is ripened at tropical ambient temperature (27°C) the peel fails to degreen
although the pulp has softened. However, the peel will degreen to a yellow
colour when the fruit is ripened at 18°C. The inability of the peel to
degreen could be because of the retention of thylakoid membranes in the plastids
and chlorophyll during the ripening process. A study was carried out to investigate
the relationships between plastid ultrastructure, chlorophyll content, and
peel colour of Cavendish banana ripened at 18±2°C (C18) and 27±2°C
(C27). The peel of Cavendish banana underwent complete degreening when the
fruit was ripened at a temperature of 18°C to produce a yellow fruit at
ripening stage (RS) 6, after 9 days of treatment. In contrast, bananas exposed
to 27°C failed
to degreen. By day 5 after ripening initiation, the pulp had softened to eating-ripe
in those fruit and brown specks appeared on the fruit peel indicating that
senescence had begun. Transmission electron microscopy revealed that the grana-thylakoid
membranes of peel chromoplasts had lysed by RS 6 in C18 fruit and only 40%
of the total chlorophyll content from RS 1 was retained. In contrast, the grana-thylakoid
membranes in C27 at day 5 were retained, along with retention of 57% of total
chlorophyll content. Total chlorophyll content of C27 fruit correlated significantly
with L*, C*, and h° colour values. The higher percentage of total chlorophyll
retained in C27 compared with C18 fruit did not fully unmask the existing peel
carotenoids, thus producing a pale-green fruit.
Keywords banana degreening; chloroplast; grana; thylakoid
membrane; chromoplast
New Zealand Journal of Crop and Horticultural Science, 2007, Vol. 35:
201–210
0014–0671/07/3502–0201 © The Royal
Society of New Zealand 2007
H05133; Online publication date 15 May 2007. Received 31 October 2005;
accepted 10 October 2006
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