Effect of environmental factors on seed germination and seedling emergence of invasive Ceratocarpus arenarius

Ceratocarpus arenarius is a problematic and noxious weed of dryland farming in North Khorasan, Iran. Experiments were conducted to investigate the mechanism of seed dormancy, as well as the effect of environmental factors on germination and emergence of this species. Results showed that the pericarp is the major obstacle to seed germination; seeds without an intact pericarp had germination rates exceeding 90%. Ceratocarpus arenarius had identical germination rates in either light/dark and continuous dark conditions, indicating that this weed species is non-photoblastic. Germination was >35% over a range of alternating light/dark temperatures (10/5, 20/10, 25/15, 30/20 and 35/25 degrees C), with maximum germination (96%) at 25/15 degrees C. Ceratocarpus arenarius seeds germinated at rates >20% in high levels of salinity (800 mm) and osmotic potential (-1 MPa), indicating that this species is tolerant to saline conditions and drought stress during germination and early seedling growth. Maximum germination of C.arenarius seeds occurred at a pH range of 79. Seedlings emerged from burial depths ranging from 0 (without covering with filter paper) to 6 cm, and the maximum emergence (94%) was observed in seeds placed on the soil surface covered with three layers of filter paper. This suggests that minimum- and no-till systems would increase seedling emergence of this species through maintaining crop residues and seeds on the soil surface. These attributes, coupled with tolerance to salinity and drought stress during germination, should be taken into account when managing C.arenarius.