Effects of soil temperature regimes after fire on seed dormancy and germination in six Australian Fabaceae species

In addition to direct fire cues such as heat, smoke and charred wood, the passage of fire leads indirectly to changes in environmental conditions which may be able to break physical dormancy in hard-coated seeds. After a fire, the open canopy and the burnt material lying on the surface alter the thermal properties of the soil, resulting in elevated soil temperatures for long periods of time. We simulated daily temperature regimes experienced at different depths of soil profile after a summer fire. Our aim was to determine whether these temperature regimes and the duration of exposure (5, 15 and 30 days) play an important role breaking physical seed dormancy in six legumes from south-eastern Australia. Our results showed that simulated temperature regimes break seed dormancy. This effect is specially pronounced at temperatures that are expected to occur near the soil surface (0–2 cm depth). The duration of exposure interacts with temperature to break dormancy, with the highest germination rates reached after the longest duration and highest temperatures. However, the germination response varied among species. Therefore, this indirect post-fire cue could play a role in the regeneration of plant communities, and could stimulate seedling emergence independent of direct fire cues as well as in interaction with direct cues.

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Influence of environmental factors on germination and emergence ofPueraria lobata

Weed Science ◽

10.1017/s0043174500092304 ◽

1999 ◽

Vol 47 (5) ◽

pp. 585-588 ◽

Cited By ~ 15

Author(s):

David J. Susko ◽

J. Paul Mueller ◽

Janet F. Spears

Keyword(s):

Environmental Factors ◽

Seedling Emergence ◽

Soil Surface ◽

Pueraria Lobata ◽

Physical Dormancy ◽

Continuous Darkness ◽

Invasive Weed ◽

Edaphic Conditions ◽

Temperature Regimes ◽

Light Darkness

Laboratory and greenhouse studies were conducted to determine the effect of several environmental factors on seed germination and seedling emergence of the invasive weedPueraria lobata(kudzu). Germination occurred over a range of alternating temperatures from 15/6 to 35/25 C. Seed germinated equally well in alternating light/darkness and continuous darkness. At all temperature regimes, percentage germination was much greater for hand-scarified seed (95 to 100%) than for nonscarified seed (7 to 17%), indicating thatP. lobataseed possesses physical dormancy. Germination exceeded 51% in solutions with pH 5 to 9. Maximum germination (99%) was observed in distilled water at pH 5.4. Germination was greatly reduced in solutions with osmotic potentials below −0.4 MPa (28% at −0.6 MPa, and 13% at −0.9 MPa); no germination was observed at −1.3 MPa. Percentage emergence was greater than 45% at burial depths in soil of 0.5 to 10 cm, with maximal emergence (72 to 85%) at depths of 0.5 to 4 cm. Seed sown on the soil surface had low seedling emergence (< 13%). No seedlings emerged when seed was exposed to flooding for 7 d or more.Pueraria lobataseed is capable of germinating in a variety of climatic and edaphic conditions, but flooding may severely limit establishment of stands by seed.

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Seed dormancy in four Tibetan Plateau Vicia species and characterization of physiological changes in response of seeds to environmental factors

Seed Science Research ◽

10.1017/s0960258513000019 ◽

2013 ◽

Vol 23 (2) ◽

pp. 133-140 ◽

Cited By ~ 14

Author(s):

Xiaowen Hu ◽

Tingshan Li ◽

Juan Wang ◽

Yanrong Wang ◽

Carol C. Baskin ◽

...

Keyword(s):

Tibetan Plateau ◽

Seed Dormancy ◽

Germination Rate ◽

Soil Surface ◽

The Tibetan Plateau ◽

Physical Dormancy ◽

High Germination ◽

One Year ◽

Hydrotime Model ◽

Aba Biosynthesis

AbstractAlthough seed dormancy of temperate legumes is well understood, less is known about it in species that grow in subalpine/alpine areas. This study investigated dormancy and germination of four Vicia species from the Tibetan Plateau. Fresh seeds of V. sativa were permeable to water, whereas those of V. angustifolia, V. amoena and V. unijuga had physical dormancy (PY). One year of dry storage increased the proportion of impermeable seeds in V. angustifolia, but showed no effect on seed coat permeability in V. amoena or V. unijuga. Seeds of all four species also had non-deep physiological dormancy (PD), which was especially apparent in the two annuals at a high germination temperature (20°C). After 1 year of storage, PD had been lost. The hydrotime model showed that fresh seeds obtained a significantly higher median water potential [Ψb(50)] than stored seeds, implying that PD prevents germination in winter for seeds dispersed without PY when water availability is limited. After 6 months on the soil surface in the field, a high proportion of permeable seeds remained ungerminated, further suggesting that PD plays a key role in preventing germination after dispersal. Addition of fluridone, an inhibitor of abscisic acid (ABA) biosynthesis, evened-out the differences in germination between fresh and stored seeds, which points to the key role of ABA biosynthesis in maintaining dormancy. Further, fresh seeds were more sensitive to exogenous ABA than stored seeds, indicating that storage decreased embryo sensitivity to ABA. On the other hand, the gibberellic acid GA3 increased germination rate, which implies that embryo sensitivity to GA is also involved in seed dormancy regulation. This study showed that PY, PD or their combination (PY+PD) plays a key role in timing germination after dispersal, and that different intensities of dormancy occur among these four Vicia species from the Tibetan Plateau.

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Effects of depth and time of sowing on emergence of Danthonia richardsonii Cashmore and Danthonia linkii Kunth

Australian Journal of Agricultural Research ◽

10.1071/ar9931311 ◽

1993 ◽

Vol 44 (6) ◽

pp. 1311 ◽

Cited By ~ 3

Author(s):

GM Lodge ◽

AJ Schipp

Keyword(s):

New South ◽

Seedling Emergence ◽

Soil Surface ◽

Maximum Temperature ◽

Sowing Time ◽

Sand Mixture ◽

South Wales ◽

Seed Field ◽

Dry Conditions ◽

Soil Temperatures

Two experiments examined the effects of sowing time and depth (surface and 10, 25, 50 mm) on emergence of Danthonia richardsonii Cashmore and Danthonia linkii Kunth. Experiment 1 was conducted from January to December 1990 on a loam/sand mixture in boxes. Emergence was highest in both species for seeds sown onto the soil surface in summer and autumn (P < 0.05). Sowing at any depth at any time of the year, or surface sowing in winter and spring, markedly reduced emergence. Experiment 2 was conducted in the field at Tamworth, northern New South Wales from September 1991 to August 1992, on a red brown earth and a black earth. This study confirmed that emergence in both species was highest from surface sown seed. Field emergence was lowest in winter, but in contrast to experiment 1, it was higher in spring, particularly on the black earth. Seedling emergence appeared to be related to mean maximum temperature, decreasing in winter as it declined below 20�C, and increasing in spring when it was greater than 23�C. Differences in seed weight were reflected in emergence of D. richardsonii and D. linkii in experiment 1. Similar emergence was recorded for the loamlsand mixture and sand, indicating that there was little effect of texture. Phalaris aquatica L. cv. Sirosa surface sown in December had lower emergence ( P < 0.05) than both Danthonia spp., but emergence of this larger seeded cultivar was higher at depths of 10 and 25 mm. Laboratory studies to determine reasons for the low emergence of D. richardsonii and D. linkii from depth, indicated that neither had an obligate light requirement for germination. Depth, however, reduced germination (P < 0.05) compared with surface sowing of seed. Seedlings at depth also were observed to have slower rates of shoot and root elongation. In the field, the most successful establishments of D. richardsonii and D. linkii seedlings are likely to occur from surface sowings in April and May. Sowing in spring may also be possible if mean maximum soil temperatures exceed 23�C, and seedlings can establish before the onset of hot, dry conditions in summer.

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Seed germination at different temperatures and seedling emergence at different depths of Rhamnus spp

Open Life Sciences ◽

10.2478/s11535-014-0291-4 ◽

2014 ◽

Vol 9 (5) ◽

pp. 569-578 ◽

Cited By ~ 1

Author(s):

Hanan Aou-ouad ◽

Hipólito Medrano ◽

Ahmed Lamarti ◽

Javier Gulías

Keyword(s):

Seed Germination ◽

Seedling Recruitment ◽

Seedling Emergence ◽

Burial Depth ◽

Temperature Regimes ◽

Mediterranean Shrubs ◽

Different Temperatures ◽

Temperature Ranges ◽

Different Depths ◽

Rhamnus Alaternus

AbstractRhamnus alaternus and R. ludovici-salvatoris, two Mediterranean shrubs with different geographic distributions, have shown important differences in seedling recruitment capacity. The objectives of this work were to determine the ability of these species to germinate seeds under different temperature ranges, as well as the capacity of seedlings to emerge from different burial depths, in order to better understand their regeneration processes. Two different experiments were performed. In the first one, seed germination was studied in Petri dishes and in the dark at different temperature regimes: a) 5–15°C, b) 10–20°C and c) 15–25°C (12h/12h). In the second experiment, seedling emergence capacity from different burial depths (0.5, 2 and 5 cm) was tested. R. ludovici-salvatoris showed a significantly higher final germination rates, a lower dormancy period, and average time response at 10–20°C than at other temperature ranges, although differences were much greater when seeds were subjected to the 5–15°C temperature regime. By contrast, R. alaternus did not show significant differences between treatments (5–15°C and 10–20°C) in germination behavior. Seedling emergence of both species was lower and slower when seeds were buried at 5 cm. However, R. ludovici-salvatoris always showed a lower seedling emergence capacity than R. alaternus at any burial depth. The low ability of R. ludovici-salvatoris to germinate seeds and emerge between 5–15°C, even from shallow depths, is discussed in relation to its low regeneration capacity and declining geographic distribution.

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Understanding mechanisms of reduced annual weed emergence in alfalfa

Weed Science ◽

10.1614/p2002-140 ◽

2003 ◽

Vol 51 (6) ◽

pp. 876-885 ◽

Cited By ~ 23

Author(s):

H. R. Huarte ◽

R. L Benech Arnold

Keyword(s):

Field Experiments ◽

Plant Density ◽

Seedling Emergence ◽

Soil Surface ◽

Bare Soil ◽

Winter Period ◽

Soil Temperatures ◽

Bull Thistle ◽

Weed Emergence ◽

Selection Of

Field experiments were carried out at the Facultad de Agronomía, Universidad de Buenos Aires, Argentina (34°25′S, 58°25′W), to evaluate the possibility of reducing weed seedling emergence through the use of alfalfa cultivars with low levels of winter dormancy and by increasing plant density from 200 to 400 plants m−2. It was hypothesized that these treatments would alter the temperature regime and the red (R)–far-red (FR) ratio of radiation to which seeds were exposed. Responses to management treatments were recorded for bull thistle, cotton thistle, plumeless thistle, tall rocket, mustard, curly dock, and pigweed. During the alfalfa establishment year, pigweed and curly dock emergence was reduced by the nondormant cultivar established at high density. This reduction disappeared when soil beneath the canopy was fitted with heaters that mimicked bare-soil temperatures. Crop canopy presence during the establishment year was not effective in reducing mustard, cotton thistle, bull thistle, plumeless thistle, and tall rocket emergence. During the second and third years after crop establishment, the canopy of the nondormant alfalfa cultivar was effective in reducing germination of weed seeds placed on the soil surface during fall and winter. In contrast, the winter-dormant cultivar allowed the establishment of weeds during the winter period. These reductions in weed emergence were associated with a modification in the R–FR ratio perceived by the seeds located at the soil surface and could largely be removed by using FR filters to increase the R–FR ratio. These results suggest that the selection of a nondormant cultivar combined with an increase in plant density could effectively reduce weed populations in alfalfa.

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The Influence of Recent Grazing Pressure and Landscape Position on Grass Recruitment in a Semi-Arid Woodland of Eastern Australia.

The Rangeland Journal ◽

10.1071/rj9960003 ◽

1996 ◽

Vol 18 (1) ◽

pp. 3 ◽

Cited By ~ 13

Author(s):

VJ Anderson ◽

KC Hodgkinson ◽

AC Grice

Keyword(s):

Seedling Emergence ◽

Perennial Grass ◽

Soil Surface ◽

Grazing Pressure ◽

Perennial Grasses ◽

Run Off ◽

Eastern Australia ◽

Annual Grasses ◽

History Of ◽

Semi Arid

This study examined the effects of previous grazing pressure, position in the landscape and apparent seed trapping capability of soil surface micro-sites on recruitment of the perennial grass Monachather paradoxa (mulga oats) in a semi-arid woodland. Seedling emergence was counted on small plots which had been kept moist for one month. The plots were on bare ground, or at grass tussocks, or at log mounds, sited in the run-off, interception and run-on zones of paddocks that had been grazed for six years at 0.3 and 0.8 sheep equivalent/ha. Few naturally occurring perennial grass seedlings emerged on any of the sites. The level of previous grazing pressure influenced the recruitment of grasses from natural sources as well as from seed of M. paradoxa broadcast on the soil surface; significantly more grass seedlings recruited in paddocks stocked at 0.3 than at 0.8 sheep/ha. Emergence of the sown grass did not differ significantly between the three zones in the landscape, but trends in the data suggest the interception zone may have been the most favourable. Recruitment from in situ grass seed was highest in the mulga grove (run-on) zone. Most seedlings of the sown grass emerged around the bases of existing perennial grass tussocks, but recruitment of volunteer perennial and annual grasses was more evenly distributed between the mulga log-mounds and perennial grass tussocks. It is concluded that very low levels of readily germinable seed of perennial grasses remained in the soil at the end of the drought and that areas with a history of high grazing pressure have less probability of grass recruitment when suitable rain occurs.

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A Laboratory Technique to Screen Seedling Emergence of Sorghum and Pearl Millet at High Soil Temperature

Experimental Agriculture ◽

10.1017/s0014479700013168 ◽

1985 ◽

Vol 21 (4) ◽

pp. 335-341 ◽

Cited By ~ 20

Author(s):

P. Soman ◽

J. M. Peacock

Keyword(s):

Pearl Millet ◽

Seedling Emergence ◽

Soil Surface ◽

Genotypic Differences ◽

Water Tank ◽

High Soil ◽

Infra Red ◽

Soil Temperatures ◽

High Soil Temperature ◽

Clay Pots

SUMMARYApparatus was built to screen sorghum and pearl millet for seedling emergence through a hot soil surface. Seeds were sown in soil in long clay pots arranged in a steel water tank so that the top 7 cm of the pots was above the water level. The soil in the pots was heated with infra-red lamps fitted to a frame above the tank. By adjusting the height of the frame the temperature of the soil could be changed. The system allows emerging plumules to be subjected to high soil temperatures (up to 50°C) but without water stress. Both crops exhibited genotypic differences in emergence.

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Changes with time in the germination of buried scentless chamomile (Matricaria perforata Mérat) seeds

Canadian Journal of Plant Science ◽

10.4141/cjps95-049 ◽

1995 ◽

Vol 75 (1) ◽

pp. 277-281 ◽

Cited By ~ 8

Author(s):

G. G. Bowes ◽

A. G. Thomas ◽

L. P. Lefkovitch

Keyword(s):

Seed Bank ◽

Seedling Emergence ◽

Soil Surface ◽

Growing Season ◽

Early Spring ◽

First Year ◽

Temperature Regimes ◽

Buried Seed ◽

Second Year ◽

Persistent Seed Bank

Change with time in the germination of scentless chamomile (Matricaria perforata Mérat) seeds was investigated. Seeds were placed in nylon net bags, buried 7 cm deep in soil, exhumed at monthly intervals for 2 yr and allowed to germinate in temperature regimes of 10/2 °C, 20/5 °C, 25/10 °C and 35/20 °C (16/8 h), simulating temperatures found during early spring or late fall, spring or fall, summer and mid-summer on the soil surface, respectively. Exhumed and refrigerator-stored (2 °C) check seeds exhibited no yearly dormancy/nondormancy germination cycle, but mortality of buried seed increased to 36%, after 10 mo in contrast with that of the check seeds which remained low for two years. Light was required for germination during the first year but was not required for a portion of the seed during the second year. The retention of viability in buried seed explains the persistent seed bank and seedling emergence throughout the growing season when moisture and temperature are nonlimiting. Key words: Seed burial, germination, Matricaria perforata Mérat

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Effect of tillage and corn on pigweed (Amaranthusspp.) seedling emergence and density

Weed Science ◽

10.1017/s0043174500092560 ◽

1997 ◽

Vol 45 (1) ◽

pp. 120-126 ◽

Cited By ~ 38

Author(s):

Joseph O. E. Oryokot ◽

Stephen D. Murphy ◽

Clarence J. Swanton

Keyword(s):

Soil Temperature ◽

Seedling Emergence ◽

Soil Surface ◽

Seedling Density ◽

Weed Species ◽

No Till ◽

Prior Constraint ◽

Soil Temperatures ◽

Management Recommendations ◽

Moldboard Plow

We studied the effect of no-till, chisel, and moldboard plow and the presence or absence of corn on soil temperature, moisture and, subsequently, the emergence phenology and density of pigweed seedlings at 2 sites from 1993 to 1995 inclusively. Tillage significantly affected the phenology of pigweed seedling emergence only during a June drought at one site in 1994. Soil temperature and moisture, measured at 2.5-cm depths, also were unaffected by tillage. Weed phenology is usually earlier in no-till because more seeds are located closer to the surface (< 5 cm deep) in no-till, thereby reducing the delay in penetrating through the soil, and because soil temperatures and moisture are nearer the germination and emergence optima. However, pigweed seedlings are already physiologically restricted to germination depths of less than 2.5 cm regardless of tillage; therefore, this prior constraint eliminated any potential differences in emergence phenologies caused by tillage. The presence or absence of corn also did not affect soil temperatures, soil moisture, or pigweed seedling emergence phenologies. Pigweed seedling density was significantly higher in no-till; this may have been caused by increased numbers of seeds near the soil surface in no-till. The presence or absence of corn did not affect pigweed seedling density; the lack of a significant effect probably reflects high variances in density. Although necessary for most weed species, tillage may be a less important factor to consider in predicting pigweed population dynamics and subsequent management recommendations.

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Physical dormancy in seeds of six genera of Australian Rhamnaceae

Seed Science Research ◽

10.1079/ssr2004197 ◽

2005 ◽

Vol 15 (1) ◽

pp. 51-58 ◽

Cited By ~ 35

Author(s):

S.R. Turner ◽

D.J. Merritt ◽

C.C. Baskin ◽

K.W. Dixon ◽

J.M. Baskin

Keyword(s):

Seed Dormancy ◽

Restoration Ecology ◽

Hot Water ◽

Optimum Temperature ◽

Physical Dormancy ◽

South West ◽

Temperature Regimes ◽

High Germination

Physical dormancy (PY) was identified in six genera representative of Australian Rhamnaceae and subsequently was broken, based on identification of key seed dormancy characteristics: (1) isolation and classification of embryo features; (2) imbibition experiments to determine the rate and amount of water uptake in seeds; and (3) determination of optimum temperature regimes for germination. All six species had relatively large spatulate embryos. Imbibition studies showed all species possessed PY (i.e. a water-impervious seed coat) that was broken by a hot-water treatment. Alleviation of PY resulted in high germination (<70%) at 7/18°C, temperatures similar to winter in south-west Western Australia. Germination was suppressed at higher temperatures and in the presence of light. The study adds information to our knowledge of seed dormancy in Australian Rhamnaceae, and highlights the benefits of understanding dormancy states in seeds prior to evaluating dormancy-release mechanisms on wild species used in restoration ecology and horticulture.

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