THE EFFECT OF THE INITIAL RATE OF DRYING ON THE SUBSEQUENT ABILITY OFIMMATURE SEEDS OF NORWAY MAPLE (ACER-PLATANOIDES L) TO SURVIVE RAPID DESICCATION

The viability of Norway maple seeds harvested at mass maturity (57.3% moisture content) was reduced from 100% to only 38% if dried rapidly ( at 15% RH and 15 degrees C for 3 days) to 4.7% moisture content. In co ntrast, slow drying for 32 days (the optimum duration of several inves tigated) to 29.9% moisture content enabled 93% of the seeds to survive subsequent rapid desiccation to 3.5% moisture content. This is simila r to the 95% viability shown by seeds harvested 40 days after mass mat urity and then dried rapidly to 4.4% moisture content. However, fruits or seeds harvested at mass maturity and then held moist for 21 days a lso showed 94 and 91% viability after subsequent rapid desiccation to 3.8 and 3.3% moisture content, respectively. Thus a post-ovule-absciss ion programme is required before Norway maple seeds are able to tolera te rapid enforced desiccation to low moisture contents, but loss in mo isture during this period is not essential to the development of desic cation tolerance.