Weed life history: identifying vulnerabilities - Ecological Management of Agricultural Weeds - page 51

Table 2.3. Factors associated with tillage that have been shown to promote the
germination of weed seeds

Factor Factor

Factor Species (%) a,b (%) a,b Reference

Light Alopecurus myosuroides 86 0 Froud-Williams (1985)

Amaranthus retroflexus 98 14 Kigel (1994)

Brassica arvensis 78 53 Povilaitis (1956)

Datura ferox 96 1 Scopel,Ballaré & Sánchez (1991)

Lolium multiflorum 95 82 Schafer & Chilcote (1970)

Poa annua 89 1 Froud-Williams (1985)

Portulaca oleracea 28 12 Povilaitis (1956)

Alternating Poa annua 92 47 Froud-Williams (1985)

temperature Rumex crispus 100 0 Totterdell & Roberts (1980)

Sonchus arvensis 57 3 Håkansson & Wallgren (1972)

Sorghum halepense 20 7 Ghersa,Benech Arnold &

Martinez-Ghersa (1992)

Stellaria media 93 47 Roberts & Lockett (1975)

Nitrate Chenopodium album 92 55 Williams & Harper (1965)

Erysimum cheiranthoides 89 57 Steinbauer & Grigsby (1957 a )

Plantago lanceolata 48 25 Pons (1989)

Plantago major 93 3 Steinbauer & Grigsby (1957 b )

Notes:
a

Factor: seeds germinated in light,in alternating temperature regime,and in nitrate solution.
Factor: seeds germinated in dark,at constant temperature equal to the mean ofthe
alternating regime,and in water.
b The numbers given for percentage germination are mostly means taken over several chilling
treatments,populations,seed types,etc.,but not over treatments that involve variation in
other factors listed in the table.In a few cases,the numbers are from selected treatments that
demonstrate the effect.

mination (Wesson & Wareing, 1969 b ; Holm, 1972), the effect could not be
attributed to improved oxygen availability alone. Holm (1972) further
observed that imbibed Abutilon theophrasti and Ipomoea purpurea produced
ethanol, acetone, and acetaldehyde when oxygen concentrations dropped
below 6% and demonstrated that these compounds inhibited germination of
seeds, even in normal air. He therefore proposed that moderate reduction in
oxygen by respiration in the soil results in anaerobic seed metabolism, which
produces volatile germination inhibitors.In the absence of air exchange,these
enforce seed dormancy. Thus, tillage probably prompts germination of weed
seeds both by venting volatile inhibitors from the surface soil and by moving
deeply buried seeds to near-surface conditions where air exchange is
improved.
Although ethylene and carbon dioxide concentrations are also commonly