ANAEROBIOSIS AS A STIMULUS TO GERMINATION IN TWO VERNAL POOL GRASSES

Tuctoria greenei and Orcuttia californica are two aquatic annual grasses in the small tribe Orcuttieae. They are endemic to seasonal pool habitats in California and Baja California. In years of poor rainfall their seed banks remain dormant until a season of rainfall which is adequate to fill the pool basins. This study attempts to elucidate the factors responsible for cuing germination. Tuctoria greenei germination is almost entirely dependent upon a combination of anaerobic conditions and light. It is suggested that in nature, such cues would be relatively specific to the uppermost soil substrate overlain by water. Orcuttia californica germination exhibits far less dependence upon anaerobic conditions. There is some indirect evidence that fungi may play an important role in stimulating germination of this species.