Germination of Artemisia sphaerocephala (Asteraceae), occurring in the sandy desert areas of Northwest China

Artemisia sphaerocephala is a dominant perennial shrub in large areas of ac tive and stabilized sands of the deserts of northwest China. A. sphaeroceph ala produces achenes in three colours that germinate at different rates but reach the same final germination percentages. The seeds are covered by a t hick pericarp which becomes a mucilaginous layer when wetted and increases in weight 589 times by absorbing water. These achenes float on water for a long time and varying concentrations of salt solutions affect germination. The achenes germinate in light but not in dark. The optimal germination tem perature is 25 degrees C. At 10 degrees C and 30 degrees C germination was slow and reached low percentages. Germination was inhibited at 5 degrees C. The deeper the achenes in sand, the lower and slower their germination. No seedlings emerged from achenes located 2 cm and deeper. However, when the upper layer of sand was removed leaving 0.5 cm, their germination reached t he same percentages as the achenes located 0.5 cm deep from the beginning o f wetting, but at a faster rate. The higher the sand moisture content, from 1.7% to 14.7%, the higher and earlier the germination. From 19.4% moisture content germination was delayed and seedlings remained undeveloped.