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Seed Size Effects on Seedling Emergence of Desert Psammophytes in China

To investigate the effects of seed size on the behavior of seeds and seedlings in sand, seedling emergence from sand was examined in Caragana korshinskii (Fabaceae; mean seed weight 65 mg) and Atraphaxis bracteata (Polygonaceae; mean seed weight 5.7 mg), two shrubs with nonphotoblastic seeds that grow on desert sand dunes in China. Seeds were sown at depths of 0 to 50 mm in sand-filled pots, and the pots were irrigated under different regimes. The results suggest that for both species, a high proportion of the seeds buried fairly deep germinate during the summer rainy season with or without producing emergent seedlings, whereas at shallow depths, where moisture is more likely to be lost by evaporation, some proportion of the seeds remain ungerminated and viable. Comparison of results in this study with those on several smaller-seeded species used in our previous studies shows that larger seeds did not always give rise to seedlings capable of emerging from deeper depths in sand. We suggested that for nonphotoblastic seeds, seed size is not a crucial determinant of the proportion of seeds that produce emergent seedlings in field conditions.