New Zealand Journal of Crop and Horticultural Science abstracts

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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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