MINIMUM TEMPERATURE AND HEAT SUM FOR SEED GERMINATION AND SEEDLING EMERGENCE OF ASPARAGUS

The effect of different temperature levels (7.5-30°C) on the time needed for seed germination and seedling emergence of asparagus (Asparagus officinalis L.) was determined. Seed germination was carried out on filter paper in petri dishes. Seeds were sown in a peat substrate at the depth of 3 cm and covered with sand in the investigations on emergence. The time needed for germination and seedling emergence was estimated as the number of days until 50% of the germinating seeds had germinated or 50% of the seedlings had emerged, respectively. The seeds started to germinate after a few days at the highest temperature levels and after about 20 days at 10°C. A big difference in number of days between the beginning and the end of germination and of seedling emergence was found at low temperature. Also at lower temperatures, a large difference between time of seed germination and seedling emergence was observed, amounting to about 50 days at 7.5°C. Regression analysis between temperature and the reciprocal values of time, enabled determination of the theoretical minimum temperature for germination and emergence. Heat sums in degree days for both germination and emergence were also determined. The obtained results show that the prediction of germination and emergence by means of heat units and minimum temperature is feasible.