Effects of Temperature, Water Potential, and Light on Germination Responses of Redroot Pigweed Seeds to Ethylene

Abstract

The responses of redroot pigweed (Amaranthus retrojixus L.) seeds to nine ethylene concentrations between 0.5 and 50 microlters per liter were assessed at different temperatures and water potentials and in either continuous white ight or darkness. Under all experimental treatments, the probit-transformed percentages increased inearly with the log of the ethylene concentration. In dormant seeds, the slope of the response line was unaffected by either light or water potential but increased with decreasing temperature. Conversely, the sope increased with increasing temperature in a partiaBy afterripened seed lot.The ethylene response threshold for germination was little affected by temperature or light, ranging from 0.2 to 0.7 microliter per liter, but decreased to less than 0.1 microliter per liter at negative water potentials. One of the main targets in weed research is the enormous reservoir ofviable dormant weed seeds present in agricultural soils (34), which escape mechanical and chemical weed control. Because buried seeds are extremely hard to kill, efforts are directed mainly toward identifying and manipulating the environmental factors that control their germination and emergence. Soil temperature and water status play key roles, and brief exposure to light during plowing can promote germination (25, 34) but the patterns of weed emergence are poorly understood. Ethylene has received increasing attention both as an endogenous or exogenous stimulant of seed germination, and as a potential tool in weed control. MATERIALS AND METHODSRedroot' pigweed seeds were collected near the Delta Branch Experiment Station at Stoneville, Mississippi, in 1973 (seed lot A) or 1977 (seed lot C) and kept in dry storage at -20 C. Both lots showed 99%o viability in tetrazolium (2, 3,5-triphenyltetrazolium chloride) tests. Seeds of lot A showed 15-20% dark germination at 30 C whereas seeds from the more dormant lot C showed only 0-2%.For each replicate, 50 sound seeds were counted onto two 1-x 3-cm strips of blotter paper moistened with distilled H20. The blotter strips were inserted into a 250-ml Erlenmeyer flask containing a 6-cm disc of blotter paper moistened with 5 ml distilled H20. The flask was closed with a serum cap through which ethylene was injected to give a known concentration within the flask. Immediately after injection, the flasks were placed in an incubator that maintained the desired temperature to within ± 1 C.Unless otherwise specified, seeds were incubated in darkness, receiving at most a brief exposure to a green safelight.Preliminary work showed that in either seed lot germination (defined as protrusion of the radicle through the seed coat) occurred within 7 days at 15 or 20 C or at -2 to -8 bars water potential, and within 3 days at 0 bars and at 25 C or higher. Thereafter, little further germination took place. Because seedlings occasionally decayed during longer incubations at high temperatures, germination was recorded after 3 days unless experimental conditions necessitated the 7-day incubation...

Temperature response in wild oat (Avena fatua L.) generations segregating for seed dormancy

“…the same trend observed in wild oat. Schonbeck & Egley (1980) found that the germination rate of dormant redroot pigweed seeds ( Amaranthus retroflexus L.) was more rapid at 25°C than at 40°C. Mares & Ellison (1989) found that freshly harvested dormant wheat grains did not germinate when imbibed at temperatures of 20°C or higher.…”

“…Cumulative germination percentages from an F 1 population incubated at 10, 15, 20 and 25°C were analysed by probit analysis ( Finney, 1971, pp. 20–30) using the methods described by Schonbeck & Egley (1980). Germination percentages were transformed to probits that result in log‐linear curves for seed populations that are normally distributed.…”

Ethylene Inhibition of Phytochrome-Induced Germination in Potentilla norvegica L. Seeds

“…2), it was not surprising that temperature changes during this period affected the ethylene inhibition most. Effects of temperature on ethylene-stimulated germination also have been noted by Schonbeck and Egley (6). Alternations of 20 (16 h) to 30°C (8 h) greatly reduced the inhibition (Fig.…”

Developmental arrest: from sea urchins to seeds

“…Anthophyta: 3, Avena fatua seed (Adkins et al, 1984a(Adkins et al, , b, 1985Cairns and De Villiers, 1986); 4, Avena sativa seed (Corbineau et al, 1991); 5, Echinochloa crus-galli seed (Taylorson, 1988;Leather et al, 1992); 6, Hordeum vulgare seed (Hareland and Madson, 1989;Fontaine et al, 1994); 7, Oryza sativa seed (Tseng, 1964;Major and Roberts, 1968;Cohn et al, 1983Cohn et al, , 1987Cohn et al, , 1989Cohn and Castle, 1984;Cohn and Hughes, 1986); 8, Panicum capillare seed (Taylorson, 1989); 9, Panicum dichotomiflorum seed (Taylorson and Hendricks, 1979;Taylorson, 1980); 10, Amaranthus albus seed (Hendricks and Taylorson, 1974;Taylorson, 1979); 11, Amaranthus retroflexus seed (Taylorson, 1979(Taylorson, , 1989Schonbeck and Egley, 1980); 12 Berbera verna seed (Hendricks and Taylorson, 1974); 13, Lactuca sativa seed (Brooks et al, 1985;Abeles, 1986); 14, Portulaca oleracea seed (Taylorson, 1979); 15, Rumex acetosella seed (French and Leather, 1979); 16. Rumex crispus seed (French and Leather, 1979;Taylorson, 1984;French et al, 1986).…”