influence of environmental factors on germination and seed storage of hoary cress (cardaria draba l.) in the soil

the effects of environmental factors on germination and emergence of hoary cress seeds were examined in laboratory and field experiments. germinability of hoary cress under light/dark conditions (90%) was significantly higher than when seeds were incubated under continuous dark (78%). hoary cress could germinate in a broad range of temperatures (15/6, 20/10, 25/15, 30/15, and 35/20?c). the germinability, however, was different depending on the temperature range and the highest and lowest germination percentages were in 15/6 (93%) and 35/20?c (72%), respectively. salinity showed significant adverse effect on germination of this weed, so that the highest germinability was at 0 concentration of nacl (92%). increased salinity levels significantly decreased hoary cress germination and its germination completely ceased at 320 mm nacl. this study indicated that hoary cress retained its germination percentage higher than 80% in the ph range of 4 to 10, so that the highest and lowest germinability was occurred at ph 10 (98%) and 4 (85%), respectively. another experiment in which seeds were buried at different depths in the field showed that the effect of interaction between burial depth and duration on seed dormancy as well as their germinability in the field and laboratory was significant and seed germination percentage was remained at high levels during the 10 months of the experiment. moreover, seed decay was not observed at any burial depths during the experiment and seed placement at burial depth of 10 cm and deeper resulted in a quiescence status of the seeds.