Induction of extreme light sensitivity in buried weed seeds and its role in the perception of soil cultivations

Light, probably acting through the photo‐receptor phytochrome, promotes germination of weed seeds when the soil is disturbed by tillage operations. A short period of burial is shown to induce an enormous ∼10000‐fold increase in light sensitivity in the seeds of the arable weed Datura ferox which is interpreted as a natural transition to the ‘very‐low‐fluence’ mode of phytochrome action. Field experiments indicated that germination of buried seeds may be triggered by millisecond‐exposures to sunlight and suggested a key role for the process of sensitization in the mechanisms whereby light requiring seeds detect the occurrence of soil cultivation events in arable lands.