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1 September 2006 Factors affecting germination of horseweed (Conyza canadensis)
Vijay K. Nandula, Thomas W. Eubank, Daniel H. Poston, Clifford H. Koger, Krishna N. Reddy
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The influence of environmental factors on germination and emergence of horseweed was examined in growth chamber experiments. Germination was highest (61%) under 24/20 C day/night temperature under light. Horseweed seed germination was observed under both light (13 h photoperiod) and complete darkness (24 h), but germination under continuous darkness was only 0 to 15% compared with 0 to 61% under light. All other experiments were conducted under 24/20 C and 13-h light conditions. Germination was 19 to 36% over a pH range from 4 to 10, with a trend toward higher germination under neutral-to-alkaline conditions. Horseweed germination was > 20% at < 40 mM NaCl concentration and lowest (4%) at 160 mM NaCl. These data suggest that even at high soil salinity conditions, horseweed can germinate. Germination of horseweed decreased from 25% to 2% as osmotic potential increased from 0 (distilled water) to −0.8 MPa, indicating that germination can still occur under moderate water stress conditions. Horseweed seedling emergence was at its maximum on the soil surface, and no seedlings emerged from seeds placed at a depth of 0.5 cm or higher.

Nomenclature: Horseweed, Conyza canadensis (L.) Cronq. ERICA.

Vijay K. Nandula, Thomas W. Eubank, Daniel H. Poston, Clifford H. Koger, and Krishna N. Reddy "Factors affecting germination of horseweed (Conyza canadensis)," Weed Science 54(5), 898-902, (1 September 2006).
Received: 5 January 2006; Accepted: 1 June 2006; Published: 1 September 2006
Osmotic stress
salt stress
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