Effect of hydration–dehydration cycles on germination of seven Calligonum species

A greenhouse experiments were conducted to study the effects of imbibition phase and hydration–dehydration cycles on the germination of seven Calligonum species, dominant shrubs in mobile sand dunes and stabilized sand field in the northern desert of China. In August 1998, seeds of Calligonum were collected and were treated by different hydration–dehydration cycles. The results show that there is not relationship between the imbibition phase and germination rate. Compared to the control, the minimum germination time for seven species was unaffected until seeds were treated to at least three hydration–dehydration cycles, cycles with delays did not alter the minimum germination time from that achieved with no hydration–dehydration cycles, all cycles treatments decreased the complete germination percentage of Calligonum rubicundum, C. gobicum, C. mongolicum, C. caput-medusae and C. arborescens.