Annual Changes in Temperature and Light Requirements for Germination of Palmer Amaranth (Amaranthus palmeri) Seeds Retrieved from Soil

Abstract

Experiments were conducted on Palmer amaranth seeds collected in 2004 and 2006 from a natural population near Pendleton, SC, to determine the temperature and light requirements for germination of seeds retrieved from soil surface or from 10-cm depth in the field. A cyclic change in seed germination of Palmer amaranth in response to temperature and light occurred during a 12-mo after-ripening period. Freshly matured seeds collected in November required mean temperatures ≥ 25 C, and natural or red (R) light for increased germination. Following after-ripening in winter, seeds experienced a reduction in dormancy and germinated higher at 25 to 35 C mean compared with 10 to 15 C mean. With after-ripening for an additional 3 mo in May, seeds experienced a broadening of thermal range (10 to 40 C mean), and germination in natural light or R light was more than twice the germination in the absence of light. Fluctuating temperatures (7.5 C amplitude) improved germination over constant temperatures, except in summer and fall (9 and 12 mo after seed maturation). Exposure of seeds to high temperatures during summer caused secondary dormancy induction. Averaged over thermal amplitudes, seeds retrieved in fall required mean temperatures > 25 C for increased germination. Burial in spring for 3 to 6 mo induced seed dormancy, and the relative germination in fall (12 mo after seed maturation) was at least 50% higher for seeds retrieved from soil surface compared to seeds exhumed from 10-cm soil depth. Seeds retrieved in late summer and fall required natural light or R light for promoting germination, whereas far-red (FR) light or darkness inhibited germination. Furthermore, the effect of R and FR light was reversible, indicating a partially phytochrome-mediated germination response of Palmer amaranth seeds following 9 to 12 mo of after-ripening in the field.

Palmer Amaranth (Amaranthus palmeri): A Review

“…5.1 cm, which had 7 7% emergence. Germination of freshly harvested Palmer amaranth seeds increased with natural light compared to those in darkness, but there were no differences in germination between seeds exposed to red and far-red light sources (Jha et al 2010a). After nine to 12 months of burial in the soil seedbank, there was a suppressive effect of far-red light and stimulant effect of red light on Palmer amaranth germination (Jha et al 2010a).…”

“…Germination of freshly harvested Palmer amaranth seeds increased with natural light compared to those in darkness, but there were no differences in germination between seeds exposed to red and far-red light sources (Jha et al 2010a). After nine to 12 months of burial in the soil seedbank, there was a suppressive effect of far-red light and stimulant effect of red light on Palmer amaranth germination (Jha et al 2010a). Light quantity experienced by the maternal plant also had an effect on Palmer amaranth seed germination; female plants grown in 87% shade produced viable seed, of which only 12% germinated in the absence of light, while female plants grown in full sunlight produced seed that allowed 25% germination under dark conditions (Jha et al 2010b).…”

Reducing the Risks of Herbicide Resistance: Best Management Practices and Recommendations

“…Seasonal changes in seed dormancy influence seed germination and ultimately emergence patterns under field conditions Baskin 1977, 1987;Honek et al 1999;Omami et al 1999). Many weeds have an annual cycle of dormancy, with the requirements for germination changing over time (Benech-Arnold et al 1988;Gallagher and Cardina 1998a,b;Jha et al 2010;Leon et al 2007;Norsworthy and Oliveria 2007a,b). With an understanding of germination and emergence requirements, emergence in the field has been predicted for many weeds with great reliability (Forcella 1993;Harvey and Forcella 1993;King and Oliver 1994;Masin et al 2005;Norsworthy and Oliveira 2007c).…”

Response of Amaranthus retroflexus L. seeds to gibberellic acid, ethylene and abscisic acid depending on duration of stratification and burial

“…A possible induction of secondary dormancy by high temperature has been shown in an experiment with A. caudatus seeds (Kępczyński and Bihun 2002). In addition, A. quitensis and A. palmeri seeds have shown a seasonal dormancy pattern (Faccini and Vitta 2005;Jha et al 2010), indicating that the behavior of seeds kept in soil is characteristic for the genus Amaranthus. Similarly, dormancy of other annual species has been released due to a low temperature during burial and reinduced by ahigh temperature (Karssen 1995 (Fig.…”