Germination Ecology of Veronica Arvensis

Abstract

SUMMARY (1) A high proportion of the freshly-matured seeds of Veronica arvensis were dormant at maturity in late May. During the summer after-ripening period, the proportion and the rate of germination increased, and the range of temperature at which seeds could germinate widened. Seeds required light for germination, and they germinated equally well at constant and alternating temperatures. By August 58-99% of the seeds germinated after 20 days in light (14-h photoperiod) at constant temperature of 10 or 15 IC, or at alternating temperatures of 15/6 and 20/100C, but none germinated at 25 IC or at the simulated August field temperature regime of 35/20 ?C. (2) Seeds in an unheated glasshouse on soil kept at field capacity and on soil that was alternately wetted and dried during summer had a low germination; 3 and 1%, respectively, in the first summer after planting, and none during the second and third summers. This lack of germination during the summer, even though light and soil moisture were not limiting, was probably because the temperature was above that required for germination. (3) By September and October the temperature in the field has fallen sufficiently to allow a high proportion of the seeds to germinate if light and soil moisture are adequate. Seeds that do not germinate during the first autumn after dispersal may germinate during the following spring or in some subsequent autumn or spring. (4) During the first year of burial, seeds came out of dormancy during summer, and by October 59-100% of exhumed seeds germinated at 15/6, 20/10, 25/15 and 30/15 OC. During winter the proportion of exhumed seeds germinating at all temperatures decreased, and in April only 38, 9 and 1% of the seeds germinated at 15/6, 20/10 and 25/15 IC, respectively, in light. This cycle of germination responses was repeated during the second summer and winter of burial. (5) As seeds require light for germination at all seasons, they cannot germinate while buried. However, seeds brought to the soil surface can germinate only in spring or autumn.