Seed dormancy as survival mechanism

• Weed seeds possess a variety of special germination mechanisms adapted to changes in temperature, moisture, aeration, exposure to light, depth of burial of seeds etc., when conditions are unfavorable for germination, they can remain dormant or delay germination.

Conditions favorable for weeds seed germination are

• Seeds of many weeds require an exposure to light for germination. This is regulated by bluish-green protein pigment called phytochrome
• Many weed seeds germinate under aerobic conditions while some require anaerobic condition. Soil turnover during ploughing and other operations exposes the seeds to light and induces germination.
• Periodicity of germination is another specialized germination mechanism. Amaranths spp have a definite pattern of peaks of germination at regular intervals.
• Summer annuals favors higher temperature & winter annuals germinate at lower temperatures some weeds germinate freely throughout the year.