Role of temperature and light in the germination ecology of buried seeds of weedy species of disturbed forests. II. Erechtites hieracifolia

1996 ◽  
Vol 74 (12) ◽  
pp. 2002-2005 ◽  
Author(s):  
Carol C. Baskin ◽  
Jerry M. Baskin
Keyword(s):  
Seed Bank ◽  
Full Range ◽  
Soil Disturbance ◽  
Seasonal Temperature ◽  
Temperature Changes ◽  
Test Conditions ◽  
Buried Seeds ◽  
Weedy Species ◽  
Dormancy Cycles

At maturity in September, about half the seeds (achenes) of Erechtites hieracifolia (Asteraceae) collected in Kentucky were dormant (did not germinate at any test condition), whereas the others were conditionally dormant (germinated only at a narrow range of test conditions). Seeds sown on top of soil in an unheated greenhouse in September failed to germinate in autumn because temperatures were below those required for germination; however, they germinated at comparable temperatures the following spring. Seeds buried in soil in September 1987 and exposed to natural seasonal temperature changes were nondormant (germinated over full range of test conditions) by April 1988, but they entered conditional dormancy by October 1988. Each October through 1995, exhumed seeds exhibited conditional dormancy. Since 89% of the seeds were viable after 8 years of burial, it appears that although seeds of this species are wind dispersed, they also have the potential to form a long-lived seed bank. Thus, soil disturbance at any time from May to September could result in establishment of plants from seeds in the seed bank. Keywords: seed dormancy, Asteraceae, dormancy cycles, buried seeds, light.

Germination requirements of Oenothera biennis seeds during burial under natural seasonal temperature cycles

1994 ◽  
Vol 72 (6) ◽  
pp. 779-782 ◽  
Author(s):  
Carol C. Baskin ◽  
Jerry M. Baskin
Keyword(s):  
Seed Banks ◽  
Late Winter ◽  
Seasonal Temperature ◽  
Oenothera Biennis ◽  
Light Requirement ◽  
Term Survival ◽  
Temperature Changes ◽  
Buried Seeds ◽  
Dormancy Cycles

Buried seeds of Oenothera biennis, which have the potential to form long-lived seed banks, were investigated to determine whether or not they (i) undergo seasonal changes in their dormancy states and (ii) require light for germination. Seeds were buried in soil and exposed to natural seasonal temperature changes. Samples of seeds were exhumed at monthly intervals for 31 months and tested for germination in light and darkness at 12-h daily thermoperiods of 15:6, 20:10, 25:15, 30:15, and 35:20 °C. At maturity in autumn, seeds germinated to 84–95% in light at 30:15 and 35:20 °C, but to 0–69% at other test conditions. By late winter, seeds germinated to 95–100% at the five thermoperiods in light and in darkness. In summer and autumn, germination in light decreased at 15:6 °C, and in darkness it dropped to 0% at 15:6 °C and decreased at 20:10, 25:15, 30:15, and 35:20 °C. Following the second winter of burial, seeds germinated to near 100% at all thermoperiods in light and darkness. Thus, seeds exhibited an annual nondormancy – conditional dormancy cycle, being nondormant from midwinter to late spring and conditionally dormant in summer and autumn. Oenothera biennis is 1 of 10 species whose seeds live for 39–40 years or longer in soil and also have an annual conditional dormancy – nondormancy cycle. Seeds of six of these species, including O. biennis, can germinate in darkness in spring or summer at simulated habitat temperatures. Therefore, a light requirement for germination is not necessarily a prerequisite for long-term survival of buried seeds, and something other than darkness prevents germination of seeds of some species buried in soil. Key words: seed banks, buried seeds, germination, dormancy cycles, light requirement, Oenothera.

Seasonal Changes in the Germination Responses of Buried Witchgrass (Panicum capillare) Seeds

Weed Science ◽  
1986 ◽  
Vol 34 (1) ◽  
pp. 22-24 ◽  
Author(s):  
Jerry M. Baskin ◽  
Carol C. Baskin
Keyword(s):  
Seasonal Changes ◽  
Late Summer ◽  
Late Spring ◽  
Seasonal Temperature ◽  
Temperature Changes ◽  
Late Autumn ◽  
Buried Seeds ◽  
Autumn And Winter

Buried seeds of witchgrass (Panicum capillare L., # PANCA) exposed to natural seasonal temperature changes in Lexington, KY, for 0 to 35 months exhibited annual dormancy/nondormancy cycles. Seeds were dormant at maturity in early October. During burial in late autumn and winter, fresh seeds and those that had been buried for 1 and 2 years became nondormant. Nondormant seeds germinated from 76 to 100% in light at daily thermoperiods of 15/6, 20/10, 25/15, 30/15, and 35/20 C, while in darkness they germinated from 1 to 24%. In late spring, seeds lost the ability to germinate in darkness, and by late summer 63 to 100% of them had lost the ability to germinate in light. As seeds became nondormant, they germinated (in light) at high (35/20, 30/15 C) and then at lower (25/15, 20/10, and 15/6 C) temperatures. As seeds reentered dormancy, they lost the ability to germinate (in light) at 15/6 C and at higher thermoperiods 2 to 3 months later.

Role of temperature and light in the germination ecology of buried seeds of weedy species of disturbed forests. I. Lobelia inflata

1992 ◽  
Vol 70 (3) ◽  
pp. 589-592 ◽  
Author(s):  
Jerry M. Baskin ◽  
Carol C. Baskin
Keyword(s):  
Seed Banks ◽  
Early Summer ◽  
Light Requirement ◽  
Forest Sites ◽  
Light Requirements ◽  
Lobelia Inflata ◽  
Buried Seeds ◽  
Weedy Species ◽  
Disturbed Forest

Lobelia inflata L. is a weedy species that may be abundant in disturbed forest sites. Temperature and light requirements for germination were determined at 12-h daily thermoperiods of 15:6, 20:10, 25:15, 30:15, and 35:20 °C for seeds exhumed after 0–28 months (September 1987 to February 1990) of burial in soil at near-natural temperatures. At maturity in autumn 1987, 2–15% of the seeds germinated after 15 days incubation at the five thermoperiods in light but 0% germinated in darkness. By January 1988, 68–100% of the seeds germinated in light at all thermoperiods except 15:6 °C. Germination at 20:10, 25:15, and 30:15 °C did not decrease to below 60% during the remainder of the study, and germination at 35:20 °C was less than 60% only four times. Germination at 15:6 °C was erratic with peaks in spring 1988, and in spring to early summer and autumn 1989. Regardless of the season in which seeds were exhumed, they did not germinate in darkness. In a laboratory study, stratification at 5 °C broke dormancy but did not substitute for the light requirement. Seeds of L. inflata have the potential to form long-lived seed banks, and buried seeds can germinate at any time during the growing season if exposed to light. Key words: seed dormancy, seed germination, buried seeds, Lobelia inflata, stratification.

Will the sleeping beauties wake up? Seasonal dormancy cycles in seeds of the holoparasiteCuscuta epithymum

2009 ◽  
Vol 20 (1) ◽  
pp. 23-30 ◽  
Author(s):  
Klaar Meulebrouck ◽  
Kris Verheyen ◽  
Martin Hermy ◽  
Carol Baskin
Keyword(s):  
Room Temperature ◽  
Empirical Studies ◽  
Seasonal Temperature ◽  
Natural Conditions ◽  
Temperature Changes ◽  
Physiological Dormancy ◽  
Spring Temperatures ◽  
Viable Seeds ◽  
Cyclic Changes ◽  
Dormancy Cycles

AbstractSeed banks are often crucial for the survival of plant species, especially short-lived ones. Nevertheless, empirical studies about the fate of seeds under natural conditions are scarce, particularly for parasitic plants. Therefore, fresh seeds of the holoparasiticCuscuta epithymumwere buried in the field under natural conditions in Belgium or kept at room temperature for up to 31 months, and germination was tested periodically by incubating seeds in light at 23°C. BuriedC. epithymumseeds had cyclic changes in their germinability, while those stored dry at room temperature never germinated without scarification. Buried seeds exhibited a seasonal cycle of physiological dormancy, the first to be reported for a species with combinational (i.e. physical+physiological) dormancy. The physiological dormancy of the embryo was broken during winter ( ≤ 5°C) but induced during exposure to late spring temperatures (>10°C). Therefore, germination ofC. epithymumseeds is fine tuned to seasonal temperature changes. Each year only a portion of the viable seeds could germinate. The portion of seeds buried in the soil that remained available for delayed germination, i.e. in the seed bank, decreased rather quickly, with only 8.5% of them being viable after 31 months of burial; all seeds stored in the laboratory remained viable. Nonetheless, we concluded that someC. epithymumseeds are capable of surviving for several years in the soil. These data indicate that the parasite is well adapted to survive in a dynamic heathland landscape where conditions for survival change constantly, but it is still sensitive to local extinction.

Are wildfires an adapted ecological cue breaking physical dormancy in the Mediterranean basin?

2015 ◽  
Vol 25 (2) ◽  
pp. 120-126 ◽  
Author(s):  
Ganesh K. Jaganathan
Keyword(s):  
Mediterranean Ecosystems ◽  
Seasonal Temperature ◽  
Dormancy Breaking ◽  
Physical Dormancy ◽  
Anatomical Structures ◽  
Temperature Changes ◽  
Seed Mortality ◽  
Fire Environment ◽  
Impermeable Seed Coat

AbstractMany studies have claimed that fire acts as the chief ecological factor cueing dormancy break in seeds with a water-impermeable seed coat, i.e. physical dormancy (PY), in Mediterranean ecosystems. However, a proposal is made that seasonal temperature changes must be viewed as more meaningful dormancy-breaking cues because: (1) fire is erratic and may break PY in seasons during which seedlings cannot complete their life cycle; (2) fire may not occur for long periods, thereby only providing an opportunity for dormancy break and germination once in every several years; and (3) if fire opens the specialized anatomical structures called ‘water gaps’, in seconds, their evolutionary role of detecting environmental conditions becomes irrational. Although fire breaks dormancy in a proportion of seeds, given the risk of seed mortality and the post-fire environment providing cues for dormancy break, it is suggested that fire might possibly be an exaptation.

scholarly journals “Active” Weed Seed Bank: Soil Texture and Seed Weight as Key Factors of Burial-Depth Inhibition

Agronomy ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 210
Author(s):  
Stefano Benvenuti ◽  
Marco Mazzoncini
Keyword(s):  
Seed Bank ◽  
Soil Texture ◽  
Seed Weight ◽  
Clay Soil ◽  
Soil Surface ◽  
Burial Depth ◽  
Weed Seed ◽  
Buried Seeds ◽  
Persistent Seed Bank

The ability of weeds to survive over time is highly dependent on an ecological strategy that ensures a high level of viable seed remains in the soil. Seed bank persistence occurs because of the specific characteristics of seed dormancy and longevity and the hypoxic microenvironment, which surrounds the buried seeds. These experiments investigate the role of soil texture, burial depth, and seed weight in seed bank dynamics. Seeds of twelve weed species are sown at increasing depths in various soil textures, and emergence data are used to detect the burial depth at which 50% and 95% inhibition is induced, using appropriate regressions. Clay soil is found to increase the depth-mediated inhibition, while it is reduced by sandy particles. In each soil texture, the highest level of inhibition is found for the smallest seeds. Seed weight is found to be closely related to the maximum hypocotyl elongation measured in vitro, and consequently, the seedlings are unable to reach the soil surface beyond a certain depth threshold. However, the threshold of emergence depth is always lower than the potential hypocotyl elongation. The depth-mediated inhibition of buried seeds is even more pronounced in clay soil, highlighting that the small size of clay particles constitutes a greater obstacle during pre-emergence growth. Finally, the role of soil texture and weed seed size are discussed not only in terms of evaluating the layer of “active” seed bank (soil surface thickness capable of giving rise to germination and emergence), but also in terms of developing a consistent and persistent seed bank. Finally, the role of soil texture and weed seed size are discussed, and the layer of “active” seed bank (the soil surface thickness that enables germination and emergence) is assessed with the aim of developing a consistent and persistent seed bank. Assessing seed bank performance when buried under different soil textures can help increase the reliability of the forecast models of emergence dynamics, thus ensuring more rational and sustainable weed management.

Does Seed Dormancy Play a Role in the Germination Ecology ofRumex crispus?

Weed Science ◽  
1985 ◽  
Vol 33 (3) ◽  
pp. 340-343 ◽  
Author(s):  
Jerry M. Baskin ◽  
Carol C. Baskin
Keyword(s):  
Seed Dormancy ◽  
Growing Season ◽  
Seasonal Temperature ◽  
Rumex Crispus ◽  
Temperature Changes ◽  
Germination Ecology ◽  
Buried Seeds ◽  
Buried Seed

Seed dormancy does not play a role in the germination ecology of curly dock (Rumex crispusL. ♯ RUMCR). This study confirms reports that freshly matured seeds are nondormant, and it shows that buried seeds exposed to natural seasonal temperature changes remain nondormant. From October 1981 through June 1983, seeds exhumed at monthly intervals germinated 80 to 100% at all thermo-periods. These results do not support suggestions that seeds of curly dock buried in soil enter dormancy. However, the results do explain why seeds of this species in the Beal and Duvel buried-seed experiments germinated when exhumed at various times during the growing season.

Top-Down Processing and Visual Reorientation Illusions in a Virtual Reality Environment

2004 ◽  
Vol 63 (3) ◽  
pp. 143-149 ◽  
Author(s):  
Fred W. Mast ◽  
Charles M. Oman
Keyword(s):  
Virtual Reality ◽  
Visual Processing ◽  
Line Length ◽  
Perceptual Cues ◽  
Virtual Reality Environment ◽  
Top Down ◽  
Test Conditions ◽  
The Subject ◽  
Processing Mechanisms

The role of top-down processing on the horizontal-vertical line length illusion was examined by means of an ambiguous room with dual visual verticals. In one of the test conditions, the subjects were cued to one of the two verticals and were instructed to cognitively reassign the apparent vertical to the cued orientation. When they have mentally adjusted their perception, two lines in a plus sign configuration appeared and the subjects had to evaluate which line was longer. The results showed that the line length appeared longer when it was aligned with the direction of the vertical currently perceived by the subject. This study provides a demonstration that top-down processing influences lower level visual processing mechanisms. In another test condition, the subjects had all perceptual cues available and the influence was even stronger.

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