Seed longevity and dormancy state in a disturbance-dependent forest herb, Ageratina altissima

AbstractDoes seed dormancy allow disturbance-oriented forest herbs such as Ageratina altissima to persist in heterogeneous natural communities? To document seed longevity and dormancy state, Ageratina seeds were buried in nylon mesh bags in second-growth forest stands in south-eastern Ohio, USA. Bags were recovered at 2-month intervals, and seeds were tested for viability and germinability in the lab. Live seed numbers declined rapidly, with seed banks exhausted in an estimated 33–37 months. Seeds showed a strong dormancy polymorphism, with 71–84% of live seeds germinable between March and July, the season of natural seedling emergence. At other dates, most seeds appeared to be in a state of induced dormancy, allowing little (0–21%) germination. The slope aspect of the burial site, an important factor controlling above-ground vegetation, had no effect on seed longevity or dormancy condition. Dormancy in Ageratina appears to be adapted to allow opportunistic germination in late spring–early summer, but to prevent germination in less benign periods. Seed longevity is shorter than the natural frequency of gaps in mesophytic forest. We conclude that a long-term dispersal/dormancy trade-off is probably an oversimplification of the spatial ecology of this species. The primary function of dormancy appears to be short-term tracking of seasonal variation.

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Morphophysiological dormancy and germination ecology in diaspores of the subtropical palm Phoenix canariensis Chabaud

Botany ◽

10.1139/cjb-2021-0126 ◽

2021 ◽

Author(s):

Lanlan He ◽

Ganesh K. Jaganathan ◽

Baolin Liu

Keyword(s):

Seed Dormancy ◽

Seedling Emergence ◽

Primary Root ◽

Germination Percentage ◽

Early Summer ◽

Germination Ecology ◽

Phoenix Canariensis ◽

Morphophysiological Dormancy ◽

Cotyledonary Petiole ◽

Seed Dormancy And Germination

The timing of germination is a crucial event in a plant’s life cycle. Seed dormancy and germination mechanisms are important factors regulating seedling emergence. Since detailed experimental evidence for germination pattern of Phoenix canariensis colonizing sub-tropical climate is scarce, we investigated seed dormancy and germination ecology of P. canariensis. We found that the embryo is underdeveloped at the time of dispersal and doubles in size before the cotyledonary petiole (CP) protrudes through the operculum. The primary root and plumule emerge from the elongated CP outside the seed. In light/dark at 30/25°C, the CP emerged from 8% of the diaspores within 30 days and from 76% within 14 weeks. Thus, 8% of the diaspores have MD and the others MPD. Removal of the pericarp and operculum resulted in 100% germination within 5 days in light/dark at 30/25°C. Cold and warm stratification as well as treatment with GA3 significantly increased the germination speed, but the final germination percentage was not significantly increased. Seed germination was synchronized in early summer when seed dormancy was released by cold stratification in the soil over winter. A remote-tubular germination type and intricate root system provide an ecological advantage to the seedling establishment.

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Seed Dormancy and Adaptive Seedling Emergence Timing in Giant Ragweed (Ambrosia trifida)

Weed Science ◽

10.1614/ws-d-11-00049.1 ◽

2012 ◽

Vol 60 (1) ◽

pp. 19-26 ◽

Cited By ~ 25

Author(s):

Brian J. Schutte ◽

Emilie E. Regnier ◽

S. Kent Harrison

Keyword(s):

Seedling Emergence ◽

Early Spring ◽

Soil Conditions ◽

Inhibitory Influence ◽

Burial Site ◽

Crop Fields ◽

Giant Ragweed ◽

Physiological Dormancy ◽

Embryo Dormancy ◽

Time Required

Giant ragweed germination is delayed by both a physiological dormancy of the embryo (embryo dormancy) and an inhibitory influence of embryo-covering structures (covering structure-enforced [CSE] dormancy). To clarify the roles of embryo and CSE dormancy in giant ragweed seedling emergence timing, we conducted two experiments to address the following objectives: (1) determine changes in germinability for giant ragweed dispersal units (hereafter “involucres”) and their components under natural burial conditions, and (2) compare embryo and CSE dormancy alleviation and emergence periodicity between successional and agricultural populations. In Experiment 1, involucres were buried in crop fields at Columbus, OH, periodically excavated, and brought to the laboratory for dissection. Involucres, achenes, and embryos were then subjected to germination assays at 20 C. In Experiment 2, temporal patterns of seedling emergence were determined at a common burial site. Reductions in embryo and CSE dormancy were compared with controlled-environment stratification followed by germination assays at 12 and 20 C, temperatures representative of soil conditions in spring and summer. Results indicated that overwinter dormancy loss involved sequential reductions in embryo and CSE dormancy. CSE dormancy, which may limit potential for fatal germination during fall, was caused by the pericarp and/or embryo-covering structures within the pericarp. In Experiment 2, successional populations emerged synchronously in early spring, whereas agricultural populations emerged throughout the growing season. Levels of embryo dormancy were greater in the agricultural populations than the successional populations, but CSE dormancy levels were similar among populations. In 12 C germination assays, embryo dormancy levels were positively correlated with time required to reach 95% cumulative emergence (run 1:r= 0.81, P = 0.03; run 2:r= 0.76, P = 0.05). These results suggest that late-season emergence in giant ragweed involves high levels of embryo dormancy that prevent germination at low temperatures in spring.

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Modeling site-specific wild oat (Avena fatua) emergence across a variable landscape

Weed Science ◽

10.1614/ws-05-142r1.1 ◽

2006 ◽

Vol 54 (5) ◽

pp. 838-846 ◽

Cited By ~ 14

Author(s):

Eric R. Page ◽

Robert S. Gallagher ◽

Armen R. Kemanian ◽

Hao Zhang ◽

E. Patrick Fuerst

Keyword(s):

Water Potential ◽

Crop Residue ◽

Seedling Emergence ◽

Bare Soil ◽

Slope Aspect ◽

Weibull Function ◽

Wild Oat ◽

Site Specific ◽

Wheat Field ◽

The Impact

The spatial and temporal pattern of wild oat emergence in eastern Washington is affected by the steep, rolling hills that dominate this landscape. The objective of this study was to assess the impact of landscape position and crop residue on the emergence phenology of wild oat. Emergence of a natural wild oat infestation was characterized over two growing seasons (2003 and 2004), at two wheat residue levels (0 and 500 g m−2), and at five landscape positions differing in slope, aspect, and elevation in a no-till winter wheat field. Wild oat emerged 1 to 2 wk earlier at south-facing landscape positions than at north-facing landscape positions. Crop residue delayed wild oat emergence by 7 to 13 d relative to bare soil at south-facing positions in 2003 and had a reduced effect on emergence at north-facing landscape positions. Therefore, preserving surface residues tended to synchronize emergence across the landscape and may facilitate better timing of weed control where residue is present. Emergence of wild oat was modeled as a function of thermal time adjusted by water potential using a Weibull function. Temperature explained more variation in the model than water potential. This model explained much of the variability in wild oat emergence among landscape positions over these 2 yr and may be useful as a tool to predict the timing of wild oat emergence. Results also indicate that site-specific modeling is a plausible approach to improving prediction of weed seedling emergence.

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Topography-based modelling reveals high spatial variability and seasonal emission patches in forest floor methane flux

10.5194/bg-2020-263 ◽

2020 ◽

Author(s):

Elisa Vainio ◽

Olli Peltola ◽

Ville Kasurinen ◽

Antti-Jussi Kieloaho ◽

Eeva-Stiina Tuittila ◽

...

Keyword(s):

Soil Moisture ◽

Spatial Variability ◽

Boreal Forest ◽

Forest Floor ◽

Methane Flux ◽

Early Summer ◽

Ground Vegetation ◽

Small Scale ◽

Ch4 Flux ◽

Ch4 Uptake

Abstract. Boreal forest soils are globally an important sink for methane (CH4), while these soils are also capable to emit CH4 under favourable conditions. Soil wetness is a well-known driver of CH4 flux, and the wetness can be estimated with several terrain indices developed for the purpose. The aim of this study was to quantify the spatial variability of the forest floor CH4 flux with a topography-based upscaling method connecting the flux with its driving factors. We conducted spatially extensive forest floor CH4 flux and soil moisture measurements, complemented with ground vegetation classification, in a boreal pine forest. We then modelled the soil moisture with a Random Forest model using topography, based on which we upscaled the forest floor CH4 flux – this was performed for two seasons: May–July and August–October. Our results demonstrate high spatial heterogeneity in the forest floor CH4 flux, resulting from the soil moisture variability, as well as on the related ground vegetation. The spatial variability in the soil moisture and consequently in the CH4 flux was higher in the early summer compared to the autumn period, and overall the CH4 uptake rate was higher in autumn compared to early summer. In the early summer there were patches emitting high amounts of CH4, however, these wet patches got drier and smaller in size towards the autumn, which was enough for changing their dynamics to CH4 uptake. The results highlight the small-scale spatial variability of the boreal forest floor CH4 flux, and the importance of soil chamber placement in order to obtain spatially representative CH4 flux results. We recommend that a site of similar size and topographical variation would require 15–20 sample points in order to achieve accurate forest floor CH4 flux.

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Drying Rates following Priming Affect Temperature Sensitivity of Germination and Longevity of Lettuce Seeds

HortScience ◽

10.21273/hortsci.40.3.778 ◽

2005 ◽

Vol 40 (3) ◽

pp. 778-781 ◽

Cited By ~ 14

Author(s):

Andrés R. Schwember ◽

Kent J. Bradford

Keyword(s):

Seed Quality ◽

Seedling Emergence ◽

Seed Priming ◽

Seed Longevity ◽

Drying Methods ◽

Lettuce Seed ◽

Headspace Volatile ◽

Beneficial Effects ◽

Lettuce Seeds ◽

Drying Rates

Seed priming (controlled hydration followed by drying) is used to alleviate high temperature inhibition of germination and improve seedling emergence of lettuce (Lactuca sativa L.) and other species. However, seed priming can also reduce the longevity of seeds during dry storage. Alternative drying methods [i.e., slow drying or moisture content reduction (MCR) before drying] can extend seed longevity compared to conventional rapid drying procedures after priming. Three postpriming drying treatments were tested on `Conquistador' and `Genecorp Green' lettuce seeds: rapid drying, slow drying and MCR (10% fresh weight loss, then held at 100% relative humidity (RH) for 6 hours, followed by rapid drying). The effects of the postpriming treatments on seed quality and longevity were compared based upon standard germination tests, germination rates, thermogradient table tests, controlled deterioration (CD) tests, and headspace volatiles analysis. The latter may be correlated with seed longevity as release of volatiles (e.g., acetaldehyde, ethanol) is associated with lipid peroxidation. While neither slow drying nor MCR before drying restored lettuce seed longevity to that of the control (not primed) seeds, the MCR method generally gave better results in both cultivars compared to rapid drying. Among the CD test conditions used, 50 °C and 75% RH gave the most consistent results for estimating potential longevity. Headspace volatile emissions from both control and primed lettuce seeds were very low and were not well correlated with seed longevity. Alternative postpriming drying regimes can extend seed longevity while retaining the beneficial effects of priming.

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Natural regeneration of senescent even-aged beech (Fagus sylvatica L.) stands under the conditions of Central Bohemia

Journal of Forest Science ◽

10.17221/823-jfs ◽

2009 ◽

Vol 55 (No. 4) ◽

pp. 144-145 ◽

Cited By ~ 9

Author(s):

L. Bílek ◽

J. Remeš ◽

D. Zahradník

Keyword(s):

Fagus Sylvatica ◽

Natural Regeneration ◽

Seedling Emergence ◽

Ground Vegetation ◽

High Survival ◽

Outer Face ◽

Crown Cover ◽

Silvicultural Treatments ◽

The Mean ◽

Selection Harvesting

The natural regeneration of beech (<I>Fagus sylvatica</I> L.) was studied under various shelterwood densities and silvicultural treatments in senescent beech stands in Central Bohemia. Four permanent research plots differed in shelterwood density, crown cover and average relative light intensities. Between 2003 and 2007, seed production, seedling emergence and survival were followed. The mean density of beech seeds (full and empty) per 1 m<sup>2</sup> was estimated in another forest stand. In the autumn of 2003 the values were distinctly higher than those indicated for full mast years of beech. Despite high losses during the wintering of seeds, relatively low germination and high first-season mortality, the high density of 1-year-old beech seedlings indicates that these elements are not the factors which hinder natural regeneration. The thickness of the humus horizons influenced the density of young beech seedlings during all the three years. Ground vegetation was more frequent outside the crown projections of parent trees and increased with distance from the nearest tree. A reduction of crown cover to the level of 80% was an appropriate measure that assured the high survival of beech regeneration during the observed four-year period. Border cutting with the outer face oriented towards the east has to be considered as less suitable for beech regeneration than shelterwood systems and group selection harvesting.

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Effects of depth and time of sowing and over-wintering on tropical perennial grass seedling emergence in northern New South Wales

Crop and Pasture Science ◽

10.1071/cp09088 ◽

2009 ◽

Vol 60 (10) ◽

pp. 954 ◽

Cited By ~ 9

Author(s):

G. M. Lodge ◽

S. Harden

Keyword(s):

Seedling Emergence ◽

Perennial Grass ◽

Soil Surface ◽

Perennial Grasses ◽

Sowing Time ◽

Rhodes Grass ◽

Factors Affecting ◽

Nylon Mesh ◽

South Wales ◽

Digitaria Eriantha

Two studies were conducted in northern NSW to examine some of the factors affecting the successful emergence of seedlings of five species of tropical perennial grasses [Panicum coloratum var. makarikariense cv. Bambatsi (panic), Digitaria eriantha ssp. eriantha cv. Premier (digit), Chloris gayana cv. Katambora (Rhodes grass), Dichanthium aristatum cv. Floren (bluegrass), and Bothriochloa bladhii ssp. glabra cv. Swann (forest bluegrass)]. The first experiment investigated the effects of depth and time (month) of sowing on tropical perennial grass seedling emergence, while a second series of studies examined the effects of contact of dispersal/sowing units with the soil, particularly over winter, on subsequent seed germination and seedling emergence. No seedling emergence of any species occurred in September 2006 and June–August 2007. From October 2006 to May 2007 there were significant effects (P < 0.001) of species, sowing time, depth, and their interaction on predicted emergence. From December to March, predicted emergence was always lower for surface-sown caryopses compared with those sown at 10 and 25 mm depth, and Bambatsi was the only species that had >50% emergence from a depth of 50 mm. Recovery of intact caryopses from 300 μm nylon mesh bags stored in the soil for 6 and 12 months was low for all species. Similarly, predicted germination of caryopses from field soil surface and buried locations (2007 and 2008) and those from florets and coated seeds (2008) was low, indicating that these species had a poor ability to over-winter in moist soil.

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Seed heteromorphy influences seed longevity in Aegilops

Seed Science Research ◽

10.1017/s096025851800034x ◽

2018 ◽

Vol 28 (4) ◽

pp. 277-285 ◽

Cited By ~ 6

Author(s):

Filippo Guzzon ◽

Simone Orsenigo ◽

Maraeva Gianella ◽

Jonas V. Müller ◽

Ilda Vagge ◽

...

Keyword(s):

Seed Germination ◽

Field Experiments ◽

Soil Seed Bank ◽

Seedling Emergence ◽

Seed Longevity ◽

Ex Situ ◽

Bet Hedging ◽

Hedging Strategy ◽

Seed Conservation ◽

Germination Phenology

AbstractThe genus Aegilops belongs to the secondary gene pool of wheat and has great importance for wheat cultivar improvement. As a genus with only annual species, regeneration from seeds in Aegilops is crucial. In several species in Aegilops, spikes produce different seed morphs, both in size and germination patterns. However, little is known about the ecology of seed germination, nor about the seed longevity in this genus. Here we investigated the germination phenology of Ae. neglecta under laboratory and field conditions and assessed longevity of different seed morphs of five additional Aegilops species using controlled ageing tests. Large seeds were short-lived and germinated faster than small seeds in most of the species. Field experiments with Ae. neglecta showed that large seeds of the dimorphic pair germinated 3 months after dispersal in contrast to 14 months for smaller seeds. Differences in longevity were detected not only in dimorphic seed pairs, but also among seeds from different positions on the spike. Our results indicate that different longevities in seed morphs of Aegilops may reflect a different soil seed bank persistence, with smaller seeds able to maintain a higher viability after dispersal than larger ones, thereby spreading seedling emergence over two years. Differences of seed germination and longevities between seed morphs in Aegilops may have important implications for ex situ seed conservation and reinforce the hypothesis of a bet-hedging strategy in the germination ecology of this genus.

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