e-ISSN 2231-8542
ISSN 1511-3701

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Exothermic Events in Cocoa (Theobroma Cacao L.) Seeds Associated with Low Temperature Damage

Y.L. Hor And ?.C. Stanwood

Pertanika Journal of Tropical Agricultural Science, Volume 14, Issue 1, April 1991

Keywords: Theobroma cacao, differential thermal analysis, cold injury.

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Embryonic axes and cotyledon tissues from individual cocoa (Theobroma cacao L.) seeds were subjected to differential thermal analysis (DTA) to detect phase transitions (liquid to solid and solid to liquid phases) of tissue constituents. Embryonic axes at 27% to 64% moisture content (fresh weight basis) exhibited a single exotherm between -14° C to -38° C. The exotherm loas caused by the presence offreezable water and was absent in tissues dried below 27% to 15%moisture. Cotyledon tissues at moisture contents between 15 % to 27% exhibited a similar aqueous exotherm between ~19°C to -25° C. In addition, a non-aqueous exotherm was also detected between +15° C to +11° C in all tissues, irrespective of moisture content. The phase transition which occurred at this temperature (+15° C to +11° C) ivas sufficiently damaging to cotyledon function so as to prevent seed germination, although the axis remained unaffected.The importance of these exothermic events to seed death during conventional (abovefreezing) and cryogenic (sub-freezing) storage of cocoa seeds is discussed.

ISSN 1511-3701

e-ISSN 2231-8542

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