UPSI Digital Repository (UDRep)
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UPSI Digital Repository (UDRep)
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| Abstract : Perpustakaan Tuanku Bainun |
| This research explores the alternative of the easy-handled short-term storage for locally produced
cacao seeds, as well as in identifying the storage windows which are considered at frequent
intervals in the maintenance of high-quality seeds. The first study was conducted to evaluate the
physiological quality of seeds stored at different temperatures and relative humidity. The
extracted cacao seeds (PBC 123 clone) were packed in zip-lock polyethylene bags, and stored at (i)
air-conditioned room temperature, RT (25±2°C, 55±5% RH), (ii) 16°C, 14°C, 10°C, (40%, 60%, 80%
RH), and (iii) control (seeds freshly extracted from pods). Seeds were sampled every 24h (hours)
over 144h storage period. Seeds at RT and 16°C produced the highest germination characteristics
(GC) and seedling growth performances (SGP). Seeds at RT showed no variations of moisture content
(MC) (46-50%) than the control. Membrane re-establishment might have occurred due to the decreased
42% of leachate conductivity (LC) at 96h. Even with the increasing (5-36%) LC over time, seeds at
16°C, 40% RH (45-52% MC) displayed a significantly higher germination rate index than seeds at 60%
and 80% RH. Seeds at 10°C (44-54% MC) and 14°C (44-52% MC) displayed the poor GC and SGP over time.
The exposure to the field environment for seeds at 14°C, suppressed their SGP to be similar as
seeds at 10°C. In studying the physic-chemical changes affected seed quality during storage, the
second study was conducted (i) to characterize the physic-chemical and microstructural
changes within seeds affected by slow-drying and chilling during storage, and (ii) to elucidate the
accumulation of reactive oxygen species antioxidant enzymes of seeds during storage. Seeds were
packed and stored at (i) RT, (ii) 16°C, 14°C, (40% and 80% RH), and (iii) control. Seeds were
sampled every 48h over 12-days storage period. Seeds at RT and 16°C, 40% RH displayed reducing
(4-9%) MC at 4 and 10 DAS, respectively. Seeds at 16°C, 40% RH also showed a sharp rise of
respiration rate at 8 DAS. In contrast, seeds at RT displayed the lower respiration rate along
storage, with their protein content were at the same level as the control. Meanwhile, the lowest
protein content displayed by seeds at 14°C, 80% RH (decreased by 53% at 2 DAS). The rapid rise of
respiration rate at 2 and 8 DAS (3-4 times higher than the lowest values), and the highest soluble
sugars (1-3 times higher than the lowest values) were the early chilling responses displayed by
seeds at 14°C, 80% RH. Moreover, their lipid peroxidation product was the highest (increased by
9-10% at 8 DAS). DPPH scavenging activity was the lowest for seeds at RT, decreased (3-4%) at 4-6
DAS. Seeds of the same treatment demonstrated the highest antioxidant enzymes activity; SOD, APX,
POX, GR, and CAT (1-23 times higher than the lowest activity) along 12 days of storage. This is in
parallel with their lowest H2O2 (13.24-24.92 nmol/g), and vice versa with seeds at RT (26.42-38.63
nmol/g). The SEM images of seed cells stored at the higher RH (14°C and 16°C, 80% RH) visualized
the extensive structure of starch granules to fracture the plastid membranes. More damages on the
membranes and plasmolysis events were observed in the seed cells of 14°C. Even though with the
better quality observed for seeds at RT, incidence of 8-30% germinated seeds in-store, however,
reduced their storability. Therefore, the condition of 16°C, 40% RH is suggested as the alternative
to minimize physio-chemical and microstructural changes in cacao seeds, contributing among the
highest GC and minimal reductions in SGP for 12 days of storage.
Keywords: seed technology, chilling and dehydration sensitivity, physically structure
changes, antioxidant machinery system, metabolism-linked damage
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