Temporal Fulfilment of the Light Requirement for Seed Germination: an Example of its Use in Management of Rare Species

摘要

Poysonia perfomta (Rollins) O'Kane and Al-Shehbaz, and P. stonensis (Rollins) O'Kane and Al-Shehbaz are rare winter annuals found in frequently disturbed habitats, such as agricultural fields on floodplains. Both species are threatened by the loss ofhabitat, by its conversion to uses other than cultivation of annual crops. Considering the responses of the non-dormant portion of the seed set, P. perforata and P. stonensis seeds germinated to <=18% in darkness with <=10-2 weeks of light on alternatingwet/dry substrate conditions (simulating current climatic conditions) and <26% with <=4—6 weeks of light on continuously moist conditions (simulating predicted future conditions in a changed climate). This indicates that planting of crops along with any field preparation should be performed after seed dispersal (in early May) and before the seeds become photostimulated (i.e. by late July under current climatic conditions, but by late May under predicted future climatic conditions). Fields need to be harvested before seeds germinate and seedlings establish (in early September), and at very low disturbance levels since seeds are highly photostimulated in August under both climatic scenarios. Soybean (Glycine max (L.) Merr.) and maize (Zea mays L.) havebeen recommended as crops to provide an artificial means of maintaining the habitat of both Paysonia species. However, short-season forage crops should also be considered since the planting and harvesting times for them closely fit the life cycle and temporal dynamics of seed photoecology of the Paysonia species.