THE VIABILITY AND GERMINATION CHARACTERISTICS OF EXHUMED SOLANUM-MAURITIANUM SEEDS BURIED FOR DIFFERENT PERIODS OF TIME

The site, depth and duration of burial significantly influenced the viability and state of dormancy of Solanum mauritianum seeds. Burial at a depth of 15 cm was most effective in reducing the level of conditional dormancy. Secondary dormancy was not induced at any of the environmental (burial) sites when seeds were maintained at 15 cm, where light and temperature fluctuations were minimal. When buried at 4cm or maintained on the soil surface secondary dormancy was induced, particularly at the inland sites where environmental conditions such as temperature and moisture were more extreme. Conditional dormancy could generally be overcome by incubating seeds at 15/30 degrees C in the light, even after prolonged burial at unfavourable germination conditions. Gibberellic acid (500 mg l(-1)) was very effective in breaking secondary dormancy of seeds induced by storage under unfavourable conditions after burial. These results have important implications for the control of this week in commercial forests.