Germination and seedling emergence in Diplachne fusca: a semi- aquatic weed of rice fields

The native grass Diplachne fusca has become an important weed in rice fields in temperate Australia since rice cultivation began in 1922. D. fusca can develop a persistent seed bank, with 48 000 seeds m^-2 (0-6 cm depth) measured at one site 18 months after the last seed input. No seedlings emerged from depths >10 mm whereas 60% of seedlings arose from seed lying on the soil surface. Emergence was strongly inhibited by presence of litter or living pasture plants. Highest seedling density was on bare ground (1480 m^-2), but this represented <5% of the seed bank. High dormancy levels were found in seed which had been stored dry and exposed to natural weather conditions. Storage in water gave highest germination, but a single drying cycle reduced germination from 44% to 10%. Darkness inhibited germination of non-dormant seed. -from Authors