Aspects of the influence of temperature on the desiccation responses of seeds of Zizania palustris (Wild rice)
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Date
1996
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Abstract
Seeds of wild rice (Zizania palustris var. interior) have been reported to show
highest survival when dehydrated at 25 QC. It has also been reported that axis cells
sustained least damage at this drying temperature.
In the present study, a linear relationship between drying rate and dehydration
temperature was established. Whereas highest positive tetrazolium staining and lowest
leakage were recorded for seeds that were dehydrated at 25 QC, maximum germination
was recorded for seeds dried at 20 QC. A proportion of seeds showed the presence of
glasses, irrespective of the dehydration temperatures used. Parameters of the glass to
liquid transition, however, correlated with neither water content nor sugar profiles.
The ratio of raffinose to sucrose was similar among all the treatments. A
hydroperoxide test revealed a linear relationship between peroxide levels and
temperature of drying although the levels of fatty acids were not correlated with
hydroperoxide levels. Butanal levels and total aldehydes evolved, on the other hand,
showed a high negative correlation with peroxide levels. Electron microscopy showed
that the variability and relative abundance of peripheral membrane complexes (PMCs)
was the highest for cells of embryonic axes dehydrated at 25 QC and the lowest for
embryonic axes of seeds dried at 10 QC. Furthermore, intramembrane particles (IMPs)
were evenly distributed in cells of axes dried at 25 or 37 QC. In contrast, membranes of
cells of axes dehydrated at 10 QC showed large IMP-free areas. The relative abundance
of IMPs was the highest for cells of embryonic axes dried at 25 QC, and the lowest for
cells of axes dehydrated at 10 QC. From these observations, it is suggested that
membrane phase transition, with the concomitant elimination of proteins, accompanies dehydration of Z. paluslris seeds at 10 QC, whereas at 37 QC peroxidation may
predominate.
Description
Thesis (M.Sc.)-University of Natal, Durban, 1996.
Keywords
Seeds--Physiology., Germination., Seeds--Viability, Theses--Botany.