Freshly-matured seeds of Amaranthus retroflexus, Capsella bursa-pastoris, Lamium amplexicaule, Spergula arvensis, and Urtica urens (collected on 29 Oct.-3 Nov., 1999) and of Portulaca oleracea (collected on 21 Sep., 1999) were (1) incubated for 3 mo at approximated prevailing soil (5 cm below surface) temperatures of arable lands in Salinas, CA, with long (10 hr daily) or short (< 2 min weekly) exposure to light (Experiment 1); or, (2) subjected to natural temperature conditions by burial at a depth of 5 cm in the field or dry-storage in paper bags in a non-heated warehouse room (Experiment 2). For Experiment 2, after 1.5 and 3 mo, seeds were incubated for 14 d in the same manner as described above to detect temporal changes in germinability and light response. Results showed that short light exposure did not satisfy the germination requirement of freshly dispersed seeds of any species except A. retroflexus. Following burial, seeds of U. urens and A. retroflexus germinated to significantly lower percentages after long exposure compared to short exposure, whereas those of C. bursa-pastoris, L. amplexicaule, and S. arvensis responded indifferently to the light exposure conditions and those of P. oleracea retained their absolute dependence on long exposure for germination. At approximated prevailing soil temperatures, newly-matured seeds of all species, except P. oleracea (with a percent germination of 76 2), exhibited low germinability (ca. 0-11%), which increased significantly after burial in soil. Compared to burial, dry-storage essentially resulted in similar germination responses to the light conditions but with significantly lower percent germination for all species.

Key words: dry-storage, Portulaca oleracea and five other common weed species, seed burial, temporal changes in germinability and light response