GERMINATION OF OROBANCHE-CRENATA SEEDS, AS INFLUENCED BY CONDITIONINGTEMPERATURE AND PERIOD

The effects of conditioning temperature and length of the conditioning period on germination of seeds Orobanche crenata were investigated in vitro. Seed samples from Syria arid Egypt, collected in various years , were compared. Optimum temperature for conditioning was 15-20-degree s-C for Syrian seeds and 20 or 15-20-degrees-C for Egyptian seeds. At 20-degrees-C a conditioning period of 18 days was required for maximum germination. When conditioning at 20-degrees-C was prolonged beyond 7 weeks, germination decreased. This effect was more pronounced for Egy ptian seeds than for Syrian seeds. Germination of Syrian seeds was str ongly reduced after conditioning for more than 4 weeks at 15 or 10-deg rees-C. A stepwise decrease in temperature during conditioning did not enhance this effect. The results of a tetrazolium test indicated that the seeds most probably did not die but developed secondary dormancy.