The effects of environmental factors on germination and emergence of Campsis radicans seeds were examined in laboratory and greenhouse experiments. Campsis radicans pods produced numerous, papery, and small seeds (696 seeds/pod; 4 mg/seed). Seeds exhibited dormancy that was relieved (74% germination) after 2 wk of prechilling. Fluctuating temperatures and a 12-h photoperiod were required for maximum germination. Optimum conditions for C. radicans seed germination (74%) were 35/25 C (day/night, 12/12 h) with a 12-h photoperiod. Temperatures below 25/15 C or above 40/30 C were unfavorable for germination. Germination in constant temperatures or in continuous darkness was less than 15%. More than 59% of C. radicans seeds germinated at pH 5 to 9, but at pH 4 or 10 seed germination was totally inhibited. Germination was totally inhibited at osmotic stress higher than −0.2 MPa. Germination was 60% at 40 mM NaCl and 20% at 160 mM NaCl. Emergence was maximum (68%) for seeds that were placed on the soil s...

https://bioone.org/journals/weed-science/volume-48/issue-2/0043-1745(2000)048[0212:FACRSG]2.0.CO;2/Factors-affecting-Campsis-radicans-seed-germination-and-seedling-emergence/10.1614/0043-1745(2000)048[0212:FACRSG]2.0.CO;2.pdf

Factors affecting Campsis radicans seed germination and seedling emergence

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...

https://bioone.org/journals/weed-science/volume-54/issue-5/WS-06-006R2.1/Factors-affecting-germination-of-horseweed-Conyza-canadensis/10.1614/WS-06-006R2.1.pdf

Factors affecting germination of horseweed (Conyza canadensis)

Annual sowthistle has become more abundant under no-till systems in southern Australia. Increased knowledge of germination biology of annual sowthistle would facilitate development of effective weed control programs. The effects of environmental factors on germination and emergence of annual sowthistle seeds were examined in laboratory and field experiments. Seeds of annual sowthistle were able to germinate over a broad range of temperatures (25/15, 20/12, and 15/9 C day/night temperatures). Seed germination was favored by light; however, some germination occurred in the dark as well. Greater than 90% of seeds germinated at a low level of salinity (40 mM NaCl), and some seeds germinated even at 160 mM NaCl (7.5%). Germination decreased from 95% to 11% as osmotic potential increased from 0 to −0.6 MPa and was completely inhibited at osmotic potential greater than −0.6 MPa. Seed germination was greater than 90% over a pH range of 5 to 8, but declined to 77% at pH 10. Seedling emergence was the grea...

https://bioone.org/journals/weed-science/volume-54/issue-5/WS-06-047R.1/Factors-affecting-seed-germination-of-annual-sowthistle-Sonchus-oleraceus-in/10.1614/WS-06-047R.1.pdf

Factors affecting seed germination of annual sowthistle (Sonchus oleraceus) in southern Australia

Effects of environmental factors on germination and emergence of hairy beggarticks were examined in laboratory and greenhouse studies. Optimum temperature range for germination of hairy beggarticks was 25/20 to 35/30 C (day/night, 12/12 h). Germination decreased above or below this range. Temperatures below 15/10 C and above 45/40 C were unfavorable for germination. Hairy beggarticks seed can germinate under both a 12-h photoperiod and a 24-h dark regime. Seed germinated 78 to 90% in buffer solutions of pH 4 to 9. Radicle growth was more sensitive to extreme pH than germination. Osmotic stress up to −0.1 MPa had little effect on germination, but less than 3% of the seed germinated at an osmotic stress of −0.75 MPa. Hairy beggarticks seed (13%) germinated at NaCl concentration of 100 mM but failed to germinate at 200 mM NaCl. Maximum emergence occurred when seed were planted less than 1 cm deep. No seedlings emerged when planted 10 cm deep. Flooding even for a day following planting decreased emergence to 25% compared to no flooding (56%). Seedling emergence decreased sharply with a further increase in duration of flooding, and no seedlings emerged when flooding was maintained up to 28 d after planting.

R. G. Wilson

Papers

Germination and seedling development of canada thistle cirsium arvense