Effects of desiccation of the recalcitrant seeds of Carapa guianensis Aubl. and Carapa procera DC.

摘要

This study was undertaken to determine if the seeds of Carapa guianensis Aubl. and Carapa procera DC. undergo physiological, biochemical, and ultrastructural changes when they are desiccated; and to find if these changes can be used to monitor viability in Carapa. Seeds were air-dried at room temperature for 7-11 days. Samples were taken at frequent intervals and germination was tested, moisture determined, lipids extracted, and samples taken for electron microscopy. The moisture content (MC) of the embryonic axes remained high throughout the experiment. The cotyledons were drier and had a higher MC variation between individual seeds during desiccation. While Karl Fisher moisture analyses indicated no relationship between axis MC and seed viability, differential scanning calorimetry (DSC) thermograms showed a strong relationship between the melting endotherm peak onset values, enthalpy (heat content) and seed germinability. Both techniques were ineffective in determining changes in seed viability when viability remained above 50%. Analyses of the bulk lipids indicated that changes were taking place, but gas chromatography (GC) results were inconsistent from year to year. Electron microscopy (EM) examinations found that cellular contents of Carapa showed little organization when seeds were fresh, but that spherosomes accumulated as desiccation progressed. These data and those from the moisture, DSC and GC analyses, add support to the hypothesis that storage problems of recalcitrant seeds are associated with intact seed MC and with lipid composition, metabolism, and distribution in the cells.