Effect of increased concentration of soil CO₂ on intermittent flushes of seed germination in <i>Echinochloa crus‐galli</i> var. <i>crus‐galli</i>

Abstract

Soil‐buried seeds of barnyardgrass ( Echinochloa crus‐galli var. crus‐galli ) germinated from April to June in three intermittent flushes. The later two flushes of germination occurred after heavy rainfall. Carbon dioxide concentration in soil air transiently increased to 30 dm 3 m –3 after the rainfall, probably due to the increase in soil temperature and water potential. Germination of exhumed seeds was stimulated by exposure to CO 2 at 30 dm 3 m –3 . Fluctuating temperature, light, water, ethylene, and nitrate are known to promote seed germination in many species. However, of these environmental factors, within ranges found in the field, only CO 2 was effective in enhancing the germination of barnyardgrass seeds. We conclude that soil CO 2 is responsible for causing intermittent flushes of germination. Detection of vegetation gaps may be explained by the responsiveness of buried seeds to CO 2 .