Microwave soil heating reduces seedling emergence of a wide range of species including invasives

Fire seasonality (the time of year of fire occurrence) has important implications for a wide range of demographic processes in plants, including seedling recruitment. However, the underlying mechanisms of fire-driven recruitment of species with physiological seed dormancy remain poorly understood, limiting effective fire and conservation management, with insights hampered by common methodological practices and complex dormancy and germination requirements. We sought to identify the mechanisms that regulate germination of physiologically dormant species in nature and assess their sensitivity to changes in fire seasonality. We employed a combination of laboratory-based germination trials and burial-retrieval trials in natural populations of seven species of Boronia (Rutaceae) to characterize seasonal patterns in dormancy and fire-stimulated germination over a 2-year period and synthesized the observed patterns into a conceptual model of fire seasonality effects on germination. The timing and magnitude of seedling emergence was mediated by seasonal dormancy cycling and seasonal temperature cues, and their interactions with fire seasonality, the degree of soil heating expected during a fire, and the duration of imbibition. Primary dormancy was overcome within 4–10 months’ burial and cycled seasonally. Fire-associated heat and smoke stimulated germination once dormancy was alleviated, with both cues required in combination by some species. For some species, germination was restricted to summer temperatures (a strict seasonal requirement), while others germinated over a broader seasonal range of temperatures but exhibited seasonal preferences through greater responses at warmer or cooler temperatures. The impacts of fires in different seasons on germination can vary in strength and direction, even between sympatric congeners, and are strongly influenced by moisture availability (both the timing of post-fire rainfall and the duration soils stay moist enough for germination). Thus, fire seasonality and fire severity (via its effect on soil heating) are expected to significantly influence post-fire emergence patterns in these species and others with physiological dormancy, often leading to “germination interval squeeze.” Integration of these concepts into current fire management frameworks is urgently required to ensure best-practice conservation. This is especially pertinent given major, ongoing shifts in fire seasonality and rainfall patterns across the globe due to climate change and increasing anthropogenic ignitions.

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Effect of Environmental Factors on Germination and Emergence of Shortawn Foxtail (Alopecurus aequalis)

Weed Science ◽

10.1017/wsc.2017.42 ◽

2017 ◽

Vol 66 (1) ◽

pp. 47-56 ◽

Cited By ~ 12

Author(s):

Ning Zhao ◽

Qi Li ◽

Wenlei Guo ◽

Lele Zhang ◽

Lu’an Ge ◽

...

Keyword(s):

Seed Germination ◽

Osmotic Potential ◽

Control Strategies ◽

Abiotic Factors ◽

Germination Rate ◽

Seedling Emergence ◽

Soil Surface ◽

Burial Depth ◽

Effective Measure ◽

Wide Range

Shortawn foxtail is an invasive grass weed infesting winter wheat and canola production in China. A better understanding of the germination ecology of shortawn foxtail would help to develop better control strategies for this weed. Experiments were conducted under laboratory conditions to evaluate the effects of various abiotic factors, including temperature, light, pH, osmotic stress, salt concentration, and planting depth, on seed germination and seedling emergence of shortawn foxtail. The results showed that the seed germination rate was greater than 90% over a wide range of constant (5 to 25C) and alternating (15/5 to 35/25C) temperatures. Maximum germination occurred at 20C or 25/15C, and no germination occurred at 35C. Light did not appear to have any effect on seed germination. Shortawn foxtail germination was 27% to 99% over a pH range of 4 to 10, and higher germination was obtained at alkaline pH values ranging from 7 to 10. Seed germination was sensitive to osmotic potential and completely inhibited at an osmotic potential of −0.6 MPa, but it was tolerant to salinity: germination even occurred at 200 mM NaCl (5%). Seedling emergence was highest (98%) when seeds were placed on the soil surface but declined with the increasing burial depth. No seedlings emerged when seeds were buried 6-cm deep. Deep tillage could be an effective measure to limit seed germination from increased burial depth. The results of this study will lead to a better understanding of the requirements for shortawn foxtail germination and emergence and will provide information that could contribute to its control.

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Rice (Oryza sativa L.) germplasm with better seedling emergence under direct sowing in flooded paddy field

Plant Genetic Resources ◽

10.1017/s1479262118000011 ◽

2018 ◽

Vol 16 (4) ◽

pp. 352-358 ◽

Cited By ~ 1

Author(s):

Junichi Kashiwagi ◽

Koji Hamada ◽

Yutaka Jitsuyama

Keyword(s):

Paddy Field ◽

Oryza Sativa L ◽

Seedling Emergence ◽

Screening Method ◽

Paddy Fields ◽

Rice Germplasm ◽

Geographical Regions ◽

Wide Range ◽

Cultivation Practice ◽

Direct Sowing

AbstractDirect sowing of rice in a flooded paddy field is a beneficial cultivation practice for water use and labour efficiency, compared to the transplanted cultivation. However, a drastic reduction in seedling emergence under flooded paddy fields is a serious constraint especially when the seeds fell at deeper soil layers. Suitable rice germplasm for the direct sowing in flooded paddy fields could ensure the success of this cultivation practice. Instead of laborious field-based screening systems, a pot-based screening method was adopted for simplicity and efficient evaluation of seedling emergence of a subset of world rice germplasm (n = 75) at different sowing depths. As a result, two rice genotypes, ‘Vary Futsi’ (landrace from Madagascar, non-glutinous, subspecies Indica) and ‘Dahonggu’ (landrace from China, non-glutinous, subspecies Indica), with consistently better seedling emergence were identified from a wide range of rice germplasm. These genotypes could serve as excellent parents for the breeding program in developing new rice cultivars with the improved seedling emergence in flooded paddy fields. There were no significant differences in the seedling emergence rate in flooded paddy conditions among the groups from various agro-geographical regions.

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Germination ecology of wild mustard (Sinapis arvensis) and its implications for weed management

Weed Science ◽

10.1017/wsc.2021.66 ◽

2021 ◽

pp. 1-27

Author(s):

Aseemjot Singh ◽

Gulshan Mahajan ◽

Bhagirath Singh Chauhan

Keyword(s):

Salt Stress ◽

Seed Germination ◽

Seedling Emergence ◽

Radiant Heat ◽

Burial Depth ◽

Sinapis Arvensis ◽

Germination Ecology ◽

Wild Mustard ◽

Differential Adaptation ◽

Wide Range

Abstract Wild mustard (Sinapis arvensis L.) is a widespread weed of the southeastern cropping region of Australia. Seed germination ecology of S. arvensis populations selected from different climatic regions may differ due to adaptative traits. Experiments were conducted to evaluate the effects of temperature, light, radiant heat, soil moisture, salt concentration, and burial depth on seed germination and seedling emergence of two [Queensland (Qld) population: tropical region; and Victoria (Vic) population: temperate region] populations of S. arvensis. Both populations germinated over a wide range of day/night (12 h/12 h) temperatures (15/5 to 35/25 C), and had the highest germination at 30/20 C. Under complete darkness, the Qld population (61%) had higher germination than the Vic population (21%); however, under the light/dark regime, both populations had similar germination (78 to 86%). At 100 C pretreatment for 5 min, the Qld population (44%) had higher germination than the Vic population (13%). Germination of both populations was nil when given pretreatment at 150 and 200 C. The Vic population was found tolerant to high osmotic and salt stress compared with the Qld population. At an osmotic potential of −0.4 MPa, germination of Qld and Vic populations was reduced by 85% and 42%, respectively, compared with their respective control. At 40, 80, and 160 mM sodium chloride, germination of the Qld population was lower than the Vic population. Averaged over the populations, seedling emergence was highest (52%) from a burial depth of 1 cm and was nil from 8 cm depth. Differential germination behaviors of both populations to temperature, light, radiant heat, water stress, and salt stress suggests that populations of S. arvensis may have undergone differential adaptation. Knowledge gained from this study will assist in developing suitable control measures for this weed species to reduce the soil seedbank.

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Patterns of seed softening and seedling emergence of nineteen annual medics during three years after a single seed crop in southern Queensland

Australian Journal of Experimental Agriculture ◽

10.1071/ea97060 ◽

1997 ◽

Vol 37 (7) ◽

pp. 767 ◽

Cited By ~ 5

Author(s):

D. L. Lloyd ◽

G. B. Taylor ◽

B. Johnson ◽

K. C. Teasdale

Keyword(s):

Seedling Emergence ◽

Soil Surface ◽

Farming Systems ◽

The Other ◽

Research Station ◽

Hard Seed ◽

Diurnal Cycles ◽

Wide Range ◽

Burr Medic ◽

Annual Medics

Summary. To produce seed to determine the rates of seed softening of annual medics in the subtropics, 8 lines of barrel medic (Medicago truncatula), 3 lines of burr medic (M. polymorpha), 4 lines of snail medic (M. scutellata), and 1 line of each of button medic (M. orbicularis), strand medic (M. littoralis) and gama medic (M. rugosa) were grown at Warra in southern inland Queensland, in 1993. Seed of a fourth line of burr medic, a naturalised line, was harvested from Hermitage Research Station at that time. Pods were placed on the soil surface and buried at a depth of 7 cm, both in flywire envelopes and as free pods. Residual hard seed numbers were determined each year for 3 years from the envelopes, and seedlings were counted and removed from the free pods after each germination event. Patterns of softening of seeds from the same seed populations were also determined after placing them in a laboratory oven with a diurnal temperature fluctuation of 60/15° C for periods of 16, 40 and 64 weeks followed, after each time period, by 4 diurnal cycles of 35/10°C. More than 90% of the original seeds were hard. Seed softening at the soil surface ranged from 26% after 3 years in button medic to almost complete softening in the gama medic after only 2 years. Burial had little effect on the rate of softening of the button medic but about halved the rate of softening of the other lines. The barrel medics were vulnerable to losses of large numbers of seedlings which softened and germinated in January–February and the snail medics from seedlings emerging in August–December. The proportion of soft seeds recovered as seedlings in the buried compared with the surface pods was higher in the larger-seeded medics, snail and gama, and lower in the other, smaller-seeded medics. Laboratory techniques effectively ranked the medic lines for their rate of seed softening in the field and provided some insight into their seasonal patterns of seed softening. A wide range of seed softening patterns is available for fitting the requirements of various farming systems. The most appropriate pattern of softening will depend on the variability of medic seed production between years and the need for self regeneration of the medic after a cereal crop.

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Seed and Germination Biology ofDittrichia graveolens(Stinkwort)

Invasive Plant Science and Management ◽

10.1614/ipsm-d-12-00072.1 ◽

2013 ◽

Vol 6 (3) ◽

pp. 371-380 ◽

Cited By ~ 4

Author(s):

Rachel N. Brownsey ◽

Guy B. Kyser ◽

Joseph M. DiTomaso

Keyword(s):

Seed Germination ◽

Seedling Emergence ◽

Management Strategies ◽

Seed Viability ◽

Base Temperature ◽

Time Model ◽

Wide Range ◽

Total Seed ◽

Thermal Time Model ◽

Seed Characteristics

AbstractUnderstanding seed characteristics and seedling establishment patterns is essential for the development of effective management strategies for invasive annual species.Dittrichia graveolens(stinkwort) has increased its range rapidly within California since 1995, yet its biology is not well understood, which has led to poorly timed management. In this study, seed viability, germination, longevity, and dormancy, as well as seedling emergence characteristics ofD. graveolenswere evaluated in field, greenhouse, and laboratory experiments in Davis, CA, over a 2-yr period (fall 2010 to summer 2012). In the laboratory, seed germination ofD. graveolensoccurred at a wide range of constant temperatures (12 to 34 C). Cumulative germination was comparable to total seed viability (80 to 95%) at optimal germination temperatures, indicating that primary (innate) dormancy is likely absent. The base temperature for germination was identified using a thermal time model: 6.5 C and 4 C for 2010 and 2011 seed populations, respectively. In the field, seedlings emerged from fall through spring following precipitation events. A very low percentage of seedlings (2.5%) emerged in the second year after planting. Equivalent seedling emergence was observed over a wide range of light conditions (100, 50, 27, and 9% of available sunlight) in a greenhouse experiment, indicating that seed germination is not limited by high or low light. Results from these seed experiments improve our understanding of the reproductive biology of this rapidly expanding exotic annual and provide valuable information for developing effective timing and longevity of management programs.

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Ecological Characteristics of Ventenata dubia in the Intermountain Pacific Northwest

Invasive Plant Science and Management ◽

10.1614/ipsm-d-14-00034.1 ◽

2015 ◽

Vol 8 (1) ◽

pp. 57-71 ◽

Cited By ~ 19

Author(s):

John M. Wallace ◽

Pamela L. S. Pavek ◽

Timothy S. Prather

Keyword(s):

Life History ◽

Soil Moisture ◽

Pacific Northwest ◽

Seed Bank ◽

Life History Traits ◽

Seedling Emergence ◽

Management Strategies ◽

Integrated Weed Management ◽

Habitat Types ◽

Wide Range

AbstractVentenata dubia is an exotic winter annual grass that has invaded Conservation Reserve Program (CRP) lands, improved pastures, intensively managed hay fields, and rangelands within the Intermountain Pacific Northwest (PNW). Currently, producers are attempting to develop V. dubia management strategies with little knowledge of its life history traits. We conducted several studies to characterize V. dubia life history patterns. Preliminary germination trials were completed to describe primary and secondary dormancy characteristics. Field studies were conducted to evaluate (1) seed bank persistence patterns, (2) seedling emergence patterns under V. dubia litter, and (3) seedling emergence and phenological development patterns within timothy hay, CRP, and rangeland habitats. Preliminary germination trials suggest that the after-ripening period required for loss of dormancy does not exceed 30 d and that dormancy breakdown peaks at approximately 90 d, after which germination occurs over a wide range of temperatures (9 to 29 C). A small fraction (< 1%) of the seed bank remained germinable up to 3 yr after burial at 2 cm depth in a grassland habitat. Seedling emergence and survival was significantly greater under high V. dubia litter layers (100% cover) compared with bare surface during the drier study year because of higher soil moisture levels maintained under litter. Across habitat types, mean seedling emergence (50% of total) occurred between 33 and 94 growing degree days (GDD) after soil moisture rose above the permanent wilting point in the fall. Seedling emergence periodicity varied among habitat types in relation to spring seedling emergence, ranging from 0 to 13% of total emergence per year. Phenological development differed across sites and years by up to several hundred GDDs but was closely aligned to Julian days. This collection of studies improves our understanding of V. dubia life history traits and will aid integrated weed management strategies in the Intermountain PNW.

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Seed germination and seedling emergence of velvetleaf (Abutilon theophrasti) and Barnyardgrass (Echinochloa crus-galli)

Planta Daninha ◽

10.1590/s0100-83582013000200003 ◽

2013 ◽

Vol 31 (2) ◽

pp. 259-266 ◽

Cited By ~ 8

Author(s):

A. Sadeghloo ◽

J. Asghari ◽

F. Ghaderi-Far

Keyword(s):

Drought Stress ◽

Seed Germination ◽

Salinity Stress ◽

Cropping Systems ◽

Seedling Emergence ◽

Abutilon Theophrasti ◽

Medium Ph ◽

Wide Range ◽

Salinity Levels ◽

Effects Of Temperature

Abutilon theophrasti and Barnyardgrass (Echinochloa crus-galli) are major weeds that affect cropping systems worldwide. Laboratory and greenhouse studies were conducted to determine the effects of temperature, pH, water and salinity stress, and planting depth on seed germination and seedling emergence of Velvetleaf and Barnyardgrass. For Velvetleaf, the base, optimum and ceiling germination temperatures were estimated as 5, 35 and 48 ºC, respectively. Seed germination was sensitive to drought stress and completely inhibited by a potential of -0.6 MPa, but it was tolerant to salinity. Salinity stress up to 45 mM had no effect on the germination of Velvetleaf, but germination decreased with increasing salt concentration. Drought and salinity levels for 50% inhibition of maximum germination were -0.3 MPa and 110 mM, respectively. Seed germination of Velvetleaf was tolerant to a wide range of pH levels. For Barnyardgrass, the base, optimum and ceiling germination temperatures were estimated as 5, 38 and 45 ºC, respectively. Seed germination was tolerant to drought stress and completely inhibited by a potential of -1.0 MPa. Salinity stress up to 250 mM had no effect on seed germination. Drought and salinity levels for 50% inhibition of maximum germination were -0.5 MPa and 307 mM, respectively. A high percentage of seed germination was observed at pH=5 and decreased to 61.5% at acidic medium (pH 4) and to 11% at alkaline medium (pH 9). Maximum seedling emergence of Velvetleaf and Barnyardgrass occurred when the seeds were placed on the surface of the soil or at a depth of 1 cm.

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The Impact of Parthenium Weed-Amended Substrates on the Germination and Early Growth of a Range of Pasture and Crop Species

Agronomy ◽

10.3390/agronomy11091708 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1708

Author(s):

Boyang Shi ◽

Kunjithapatham Dhileepan ◽

Steve Adkins

Keyword(s):

Leaf Litter ◽

Seedling Emergence ◽

Growing Season ◽

Early Growth ◽

Agricultural Crop ◽

Crop Species ◽

Test Species ◽

Wide Range ◽

Parthenium Weed ◽

Test Plants

Parthenium weed (Parthenium hysterophorus L.) is an internationally important invasive weed native to the tropical and sub-tropical Americas, and invasive in more than 30 countries. This weed has serious adverse influences on rangeland and agricultural crop production, on human and animal health, and on the biodiversity of natural communities. Parthenium weed leaf litter can reduce seedling emergence and affect the early growth of a wide range of pasture and crop species. Soil collected from a heavily infested parthenium weed area was shown to reduce seedling emergence of a wide range of test plants (lettuce (Lactuca sativa L.), maize (Zea mays L.), curly windmill grass (Enteropogon acicularis L.), and liverseed grass (Urochloa panicoides P.Beauv.)) by between 20 to 40%; however, the soil had no effect on the subsequent growth of the surviving test plants. Soil amended with dried parthenium weed leaf litter reduced the emergence of test species by ca. 20 to 40%, but it had no effect on the growth of the surviving test plants. One week after emergence, the growth of all test species was stimulated by 9 to 86% in the leaf litter-amended soil with the increased growth matching the increased amounts leaf litter amended. In parthenium weed-infested landscapes, the substrate (soil) is affected by the plant during the growing season by the release of allelopathic chemicals. However, the plant’s litter can affect the community outside of the growing season, first through a residual allelopathic activity, but also by a fertilizing effect as litter breakdown occurs. This study demonstrates the significant ability of parthenium weed to affect plant communities throughout the year and, when considered over several years, this may lead to the creation of a complete monoculture of the weed.

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Germination ecology of Rhynchosia capitata: an emerging summer weed in Asia

Planta Daninha ◽

10.1590/s0100-83582013000200002 ◽

2013 ◽

Vol 31 (2) ◽

pp. 249-257 ◽

Cited By ~ 6

Author(s):

H.H. Ali ◽

A. Tanveer ◽

M.A. Nadeem ◽

H.N. Asghar ◽

M.M. Javaid

Keyword(s):

Seed Germination ◽

Soil Depth ◽

Seedling Emergence ◽

Ecological Factors ◽

Moisture Stress ◽

Burial Depth ◽

Seed Burial ◽

Germination Ability ◽

Wide Range ◽

The One

Rhynchosia capitata is becoming an increasing problem in summer crops, such as cotton, soybean, pearl millet and mungbean in many Asian countries. Laboratory and greenhouse studies have been conducted to determine the effects of several environmental factors on seed germination patterns and seedling emergence of R. capitata. We investigated whether the diverse ecological factors such as temperature, light, salinity, moisture stress, pH, and soil depth affected germination and seedling emergence of R. capitata. Germination increased as temperature increased from 25ºC and significantly reduced at 45ºC. Presence or absence of light did not influence germination. Germination of R. capitata was sensitive to increased salt and moisture stress, as well as to seed burial depth. Only 48% of seeds germinated at 150 mM salt concentration compared to 100% in control (distilled water). Similarly, 15% of seeds germinated at an osmotic potential of ‑0.8 MPa compared to 88% at ‑0.2 MPa. The optimum pH for seed germination of R. capitata was 7 (98% germination), but the seeds also germinated at lower level of pH 5 (85%) and at higher level of pH 10 (75%). In seed burial trial, maximum seedling emergence of 93% occurred at 2 cm depth, and seedling did not emerge from a depth of 12 cm. The high germination ability of R. capitata under a wide range of ecological factors suggests that this species is likely to be the one to cause more problems in a near future, if not managed appropriately.

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