Factors affecting turnipweed (Rapistrum rugosum) seed germination in southern Australia

Experiments were conducted on the seed of turnipwecd collected from southern Australia. Seed germinated over a range of temperatures (25/15, 20/12, and 15/9 Q under both light/dark and dark conditions. Regardless of the light condition, germination of naked seed (63 to 88%) was greater than the seed in intact silique (0 to 13%). Seed germination was relatively unaffected (greater than 60%) at a low level of salinity (80 niM NaCl), and some germination occurred even at 160 mM NaCl (11 %). Seed germination decreased as osmotic potential decreased from 0 to - 1.0 MPa; however, some germination occurred even at an osmotic potential of - 1.0 MPa (22%). Seed germination was greater than 76% over a pH range of 4 to - 10. Seedling emergence of turnipweed was greater (60%) for seed buried at I cm than on the soil surface (23%). No seedlings emerged from seed buried at 5 cm. Information gained in this study will be important in developing a better understanding of the requirements for turnipweed germination and emergence.