Soil heating and germination: investigations using leaf scorch on graminoids and experimental seed burial

2006 ◽  
Vol 15 (4) ◽  
pp. 509 ◽  
Author(s):  
Mark G. Tozer ◽  
Tony D. Auld
Keyword(s):  
Heat Shock ◽  
Seed Germination ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
Weather Conditions ◽  
Subsequent Growth ◽  
Soil Heating ◽  
Soil Level ◽  
Dead Tissue ◽  
Survival Of Seedlings

Burns conducted to reduce fuels are usually carried out under mild weather conditions. This introduces a risk that soil heating will be insufficient to trigger germination in species with a heat-shock requirement. Resprouting graminoids with leaves or culms arising from subterranean meristems can be used to estimate soil heating because the leaf is burnt to soil level and the subterranean tissue is killed to a depth dependent on the level of soil heating. Provided the meristem survives, the length of dead tissue is exposed following subsequent growth. We sought to determine whether the length of dead tissue (scorch length) was correlated with the post-fire recovery of Acacia suaveolens, a fire-sensitive shrub with seed germination dependent on heat shock. The peak emergence depth for this species varies as a function of soil heating: temperatures above 100°C induce seed death whereas temperatures below 60°C do not break dormancy. We found that average scorch length was correlated with average seedling emergence depth. However, experimental burial of scarified (i.e. non-dormant) seeds showed that the peak emergence depth was similar for seeds sown before, after or in the absence of fire. This suggests that post-germination mortality is also depth-dependent, with seedling survival reduced at depths from 0 to 20 mm. The results suggest that survival of seedlings will be enhanced if soil heating is sufficient to promote germination of seeds buried at least 20 mm deep. Scorch lengths on graminoid leaves provide an indication of whether this condition is met.

Influence of selected environmental factors on seed germination and seedling survival of the arid zone invasive species tobacco bush (Nicotiana glauca R. Graham)

2016 ◽  
Vol 38 (4) ◽  
pp. 417 ◽  
Author(s):  
Singarayer K. Florentine ◽  
Sandra Weller ◽  
Patrick F. Graz ◽  
Martin Westbrooke ◽  
Arunthathy Florentine ◽  
...  
Keyword(s):  
Invasive Species ◽  
Heat Shock ◽  
Seed Germination ◽  
Arid Zone ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Stress Factors ◽  
Burial Depth ◽  
Nicotiana Glauca

Tobacco bush (Nicotiana glauca R. Graham) is an aggressive invading species, which is active after disturbances such as high rainfall events and flooding. Past studies have focussed on population dynamics and allelopathic effects associated with the species, but little is known about its seed ecology. To address this dearth of information, this study aimed to investigate: (i) the effect of various stress factors (temperature, light, osmotic potential, salt stress, heat-shock, a combination of heat-shock and smoke, pH buffer, and burial depth of seed) on seed germination and seedling emergence, and (ii) factors affecting the fate of seedlings. The results show that N. glauca was able to germinate over a broad range of temperatures with highest seed germination occurring at 30/20°C with 12 h of light and 12 h of dark conditions. Seed germination was greatest (89%) when seeds were placed on the soil surface and emergence decreased considerably as planting depth increased from 0.5 to 1.5 cm. Water stress greatly reduced seed germination (58% germination at osmotic potentials below –0.2 MPa) and germination was completely inhibited at water potentials of –0.4 to –0.6 MPa. Although increasing salinity reduced the seed germination of this invasive species, N. glauca seed was able to germinate in both alkaline (81% at pH 10) and acidic (80% at pH 4) conditions. The trial on the effect of seed age and field seed burial on seed germination showed a slight decline in seed germination after 120 days of burial compared with non-buried seeds. Further, the combined effect of heat-shock and smoke effectively inhibited the germination of N. glauca seeds; however, our study shows that seedlings of N. glauca can withstand heat-shock of up to 130°C. Studies such as this will assist in the development of control strategies to prevent the spread of this invasive species into arid landscapes.

Bigleaf maple seedling establishment and early growth in Douglas-fir forests

1988 ◽  
Vol 18 (10) ◽  
pp. 1226-1233 ◽  
Author(s):  
Jeremy S. Fried ◽  
John C. Tappeiner II ◽  
David E. Hibbs
Keyword(s):  
Seed Predation ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
Early Growth ◽  
Douglas Fir ◽  
Stand Development ◽  
Size Distributions ◽  
Canopy Density ◽  
Successful Establishment ◽  
Survival Of Seedlings

Survival, age and height distributions, and stocking of bigleaf maple (Acermacrophyllum Pursh) seedlings were studied in 1- to 250-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stands in western Oregon to identify the stages in stand development in which bigleaf maple is most likely to establish successfully from seed. Maple seedling emergence averaged 30–40% where seeds were planted and protected from rodents but was typically <2% for unprotected seeds. Seedling survival after 2 years was highly dependent on canopy density, measured by percent sky. Average 1st-year survival of seedlings originating from planted, protected seeds was highest in clearcuts (1–2 years old, 36% survival, 56% sky) and pole-size stands (41–80 years old, 30% survival, 17% sky) with sparse understories and canopies. It was lowest in young stands with dense canopies (20–40 years old, 4% survival, 8% sky) and old stands (81–250 years old, 14% survival, 13% sky) with dense understories. Naturally regenerated populations of bigleaf maple seedlings, which occurred in aggregations (0.005–0.04 ha in area), were most abundant (up to 10 000/ha) in pole-size Douglas-fir stands. Although seedling size distributions within stands had a strongly inverse J shaped form, size distributions within aggregations appeared more normal (bell-shaped). Seedling age rarely exceeded 15 years. Seedlings grew slowly in the understory, often reaching only 25 cm in height after 8–10 years, and were intensively browsed by deer. Naturally regenerated seedlings were virtually absent from clearcuts, probably because of dense competing vegetation and lack of seed caused by poor dispersal and seed predation. The "window" for the most successful establishment of bigleaf maple seedlings appears to begin after canopy thinning and end before forbs and shrubs invade.

scholarly journals Seed encrusting with salicylic acid: A novel approach to improve establishment of grass species in ecological restoration

PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0242035
Author(s):  
Simone Pedrini ◽  
Jason C. Stevens ◽  
Kingsley W. Dixon
Keyword(s):  
Salicylic Acid ◽  
Seed Germination ◽  
Ecological Restoration ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
Field Conditions ◽  
Grass Species ◽  
Seed Coating ◽  
Seedling Density ◽  
Survival And Growth

To achieve global ambitions in large scale ecological restoration, there is a need for approaches that improve the efficiency of seed-based interventions, particularly in overcoming the bottleneck in the transition from germination to seedling establishment. In this study, we tested a novel seed-based application of the plant stress modulator compound salicylic acid as a means to reduce seedling losses in the seed-to-seedling phase. Seed coating technology (encrusting) was developed as a precursor for optimising field sowing for three grass species commonly used in restoration programs, Austrostipa scabra, Microlaena stipoides, and Rytidosperma geniculatum. Salicylic acid (SA, 0.1mM) was delivered to seeds via imbibition and seed encrusting. The effects of SA on seed germination were examined under controlled water-limited conditions (drought resilience) in laboratory setting and on seed germination, seedling emergence, seedling growth and plant survival in field conditions. Salicylic acid did not impact germination under water stress in controlled laboratory conditions and did not affect seedling emergence in the field. However, seedling survival and growth were improved in plants grown from SA treated seeds (imbibed and encrusted) under field conditions. When SA delivery methods of imbibing and coating were compared, there was no significant difference in survival and growth, showing that seed coating has potential to deliver SA. Effect of intraspecific competition as a result of seedling density was also considered. Seedling survival over the dry summer season was more than double at low seedling density (40 plants/m2) compared to high seedling density (380 plants/m2). Overall, adjustment of seeding rate according to expected emergence combined with the use of salicylic acid via coating could improve seed use efficiency in seed-based restoration.

Establishment of buffel grass, green panic and Siratro from seed broadcast into a speargrass pasture in Southern Queensland

1981 ◽  
Vol 32 (5) ◽  
pp. 749 ◽  
Author(s):  
SJ Cook ◽  
GR Dolby
Keyword(s):  
Seed Germination ◽  
Untreated Control ◽  
Seedling Survival ◽  
Panicum Maximum ◽  
Buffel Grass ◽  
Native Pasture ◽  
And Control ◽  
Germinable Seed ◽  
Main Factor ◽  
Survival Of Seedlings

The establishment and survival of seedlings from pasture seed oversown into a native speargrass (Hetevopogon contortus) pasture were studied in southern Queensland. Lime pelleted and unpelleted seed of buffel grass (Cenchrus ciliaris), green panic (Panicum maximum var, trichoglume) and Siratro (Macroptilium atvopuvpureum) were either sown into a cultivated seedbed or broadcast into native pasture pretreated as follows: untreated control; mown to 3 cm; or killed with herbicide. Buffel grass was sown both as fascicles and as caryopses. Establishment was similar in all oversown seedbeds with seedling numbers accounting for 37 % of the germinable seed sown, compared to 49% in the cultivated seedbed. Pelleting increased establishment where competition was present, the effect being greatest for Siratro and least for buffel grass fascicles. Establishment of buffel grass caryopses was markedly inferior to that of fascicles. Seedling survival rather than seed germination was the main factor influencing the success of the pasture sowing. Less than 1 % of the grass seedlings survived in the mown and control plots, but 38 % survived where competition was controlled by herbicides. Siratro survived equally as well as the grasses in the herbicide-treated plots, but survived markedly better when in competition with native grasses. Surface broadcasting into native pasture is therefore considered a satisfactory, though risky method of establishment for legumes such as Siratro, but not for grasses, unless competition is controlled.

scholarly journals Regeneration and Endogenous Phytohormone Responses to High-Temperature Stress Drive Recruitment Success in Hemiepiphytic Fig Species

2021 ◽  
Vol 12 ◽  
Author(s):  
Chuangwei Fang ◽  
Huayang Chen ◽  
Diana Castillo-Díaz ◽  
Bin Wen ◽  
Kun-Fang Cao ◽  
...  
Keyword(s):  
High Temperature ◽  
Seed Germination ◽  
Temperature Stress ◽  
Growth And Development ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
Functional Trait ◽  
High Temperature Stress ◽  
Growth Forms ◽  
Early Regeneration

Exposure to high-temperature stress (HTS) during early regeneration in plants can profoundly shape seed germination, seedling growth, and development, thereby providing stress resilience. In this study, we assessed how the timing of HTS, which was implemented as 8 h in 40°C, could affect the early regeneration stages and phytohormone concentration of four hemiepiphytic (Hs) and four non-hemiepiphytic (NHs) Ficus species. Their seed germination, seedling emergence, and seedling survival probabilities and the concentrations of three endogenous phytohormones, abscisic acid (ABA), indole-3-acetic acid (IAA), and salicylic acid (SA) were assessed after HTS imposed during imbibition, germination, and emergence. In both groups, seeds were more sensitive to HTS in the early regeneration process; stress experienced during imbibition affected emergence and survival, and stress experienced during germination affected subsequent emergence. There was no effect from HTS when received after emergence. Survival was highest in hemiepiphytes regardless of the HTS treatment. The phytohormones showed growth form- and regeneration stage-specific responses to HTS. Due to the HTS treatment, both SA and ABA levels decreased in non-hemiepiphytes during imbibition and germination; during germination, IAA increased in hemiepiphytes but was reduced in non-hemiepiphytes. Due to the HTS treatment experienced during emergence ABA and IAA concentrations were greater for hemiepiphytes but an opposite effect was seen in the two growth forms for the SA concentration. Our study showed that the two growth forms have different strategies for regulating their growth and development in the early regeneration stages in order to respond to HTS. The ability to respond to HTS is an ecologically important functional trait that allows plant species to appropriately time their seed germination and seedling development. Flexibility in modulating species regeneration in response to HTS in these subtropical and tropical Ficus species could provide greater community resilience under climate change.

Factors effecting the germination and emergence of a rangeland weed; European heliotrope (Heliotropium europaeum L.)

2018 ◽  
Vol 40 (6) ◽  
pp. 583
Author(s):  
Talia Humphries ◽  
Friedrich F. Graz ◽  
Singarayer K. Florentine
Keyword(s):  
Heat Shock ◽  
Seed Germination ◽  
Osmotic Stress ◽  
Germination Rate ◽  
Seedling Emergence ◽  
Control Treatment ◽  
Research Station ◽  
Burial Depth ◽  
South Wales ◽  
Heliotropium Europaeum

European heliotrope (Heliotropium europaeum L.) is an important weed in semiarid and arid Australia, due to its toxicity to livestock and its ability to out-compete crops for water and soil nutrients. It is an ephemeral species; populations appear in high densities when conditions are favourable, but seeds remain dormant in the soil seedbank for extended periods of time. This study aimed to identify environmental factors that promoted the germination of this weed and factors that de-vitalise seeds. Seeds were collected from the Australian semiarid zone, at Nanya Research Station, New South Wales. The effects on seed germination and seedling emergence of H. europaeum of alternating temperature, photoperiod, drought, salinity, pH range, heat shock combined with smoke exposure, and burial depth were investigated. The highest germination rate was observed under the highest temperature regime, 30/20°C, under a photoperiod of 12h light and 12h dark. The weed germinated under moderate osmotic stress, but the highest germination occurred in the control treatment (no osmotic stress). The effect of salinity and pH on percentage germination was not significant. The effect of the heat shock and smoke treatment significantly reduced seed germination, with germination inhibited when seeds were exposed to 100°C for 3min. Burial depth had a significant effect on seedling emergence, with a burial depth of 0.5cm reducing the germination by ~20%. It is recommended that further research into using fire and tillage interventions for H. europaeum be explored, as these may be used to reduce the viable seedbank of this weed, allowing long-term control to be achieved.

Seed-germination responses of Calotropis procera (Asclepiadaceae) to temperature and water stress in northern Australia

2016 ◽  
Vol 64 (5) ◽  
pp. 441 ◽  
Author(s):  
E. O. Menge ◽  
S. M. Bellairs ◽  
M. J. Lawes
Keyword(s):  
Water Stress ◽  
Seed Germination ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
Seed Mass ◽  
Calotropis Procera ◽  
Northern Australia ◽  
Germination Time ◽  
Seed Biology ◽  
Mean Germination Time

Understanding the seed biology of the introduced weed rubber bush (Calotropis procera (Aiton, W.T.Aiton)) is critical to its management in northern Australia. We examined the numbers of seeds produced and the effects of environmental temperature and water stress on germination performance (germinability G; mean germination time MGT) of rubber bush seeds from across northern Australia. Germination trials were conducted using seeds from wild populations monitored for 3 years. Seed numbers per fruit did not vary significantly among the six populations studied (mean ± s.e. = 433.2 ± 19.0), but seed mass did (range from 8.32 ± 0.24 to 5.24 ± 0.06 mg), with no negative correlation between the measures. Maximum seed germination (68–100%) occurred at 30°C, associated with a mean germination time of 2.58 days. Under water stress, the proportion of germinated seeds declined significantly with increasing temperature from 92.5 ± 1.1% at 20°C and 0 MPa to 2.8 ± 1.7% at 40°C and –0.4 MPa respectively. Seeds were unable to germinate at ambient temperatures ≥40°C, but remained quiescent and hence viable. Planting depth influenced seedling emergence, with minimal germination of seeds on the surface (5.8%) but 88.5% germination at 3-cm depth. The effect of water stress was dependent on temperature, with water stress inducing a reduction in optimum germination temperature from 30°C to 20°C. Phenotypic plasticity in G and MGT did not show clear patterns among populations or years. Short MGTs increase seedling survival by rapid transition from endosperm resources to photosynthesis, whereas seed quiescence (cf. dormancy) optimises germination opportunities in a semiarid environment. Thus, the germination traits reported in the present study are likely to promote seedling survival and potential spread of rubber bush in semiarid Australia.

scholarly journals Effect of Environmental Factors on the Germination and Emergence of Drunken Horse Grass (Achnatherum inebrians)

Weed Science ◽  
2020 ◽  
pp. 1-29
Author(s):  
Yonghuan Yue ◽  
Guili Jin ◽  
Weihua Lu ◽  
Ke Gong ◽  
Wanqiang Han ◽  
...  
Keyword(s):  
Seed Germination ◽  
Environmental Factors ◽  
Abiotic Factors ◽  
Seedling Emergence ◽  
Management Strategies ◽  
Germination Percentage ◽  
Western China ◽  
Burial Depth ◽  
Achnatherum Inebrians ◽  
Water Ph

Abstract Drunken horse grass [Achnatherum inebrians (Hance) Keng] is a perennial poisonous weed in western China. A comprehensive understanding of the ecological response of A. inebrians germination to environmental factors would facilitate the formulation of better management strategies for this weed. Experiments were conducted under laboratory conditions to assess the effects of various abiotic factors, including temperature, light, water, pH and burial depth, on the seed germination and seedling emergence of A. inebrians. The seeds germinated at constant temperatures of 15, 20, 25, 30, 35°C and in alternating-temperature regimes of 15/5, 20/10, 25/15, 30/20, 35/25, 40/30°C, and the seed germination percentages under constant and alternating temperatures ranged from 51% to 94% and 15% to 93%, respectively. Maximum germination occurred at a constant temperature of 25°C, and germination was prevented at 45/35°C. Light did not appear to affect seed germination. The germination percentage of seeds was more than 75% in the pH range of 5 to 10, with the highest germination percentage at pH 6. The seeds germinated at osmotic potentials of 0 MPa to -1.0 MPa, but decreasing osmotic potential inhibited germination, with no germination at -1.2MPa. After 21 d of low osmotic stress, the seeds that did not germinate after rehydration had not lost their vitality. The seedling emergence percentage was highest (90%) when seeds were buried at 1 cm but declined with increasing burial depth and no emergence at 9 cm. Deep tillage may be effective in limiting the seed germination and emergence of this species. The results of this study provide useful information on the conditions necessary for A. inebrians germination and provide a theoretical basis for science-based prediction, prevention and control of this species.

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