Seed Germination Ecology Research Articles

Germination ecology of heteromorphic seeds of slender Russian thistle (Salsola collina)

Abstract Slender Russian thistle (Salsola collina Pall.) is a troublesome weed distributed mainly in the cropping regions of northern China that produces heteromorphic seeds in the same plant. However, limited information is available on the germination ecology of heteromorphic seeds in S. collina. Thus, the present study was conducted to verify the effect of alternating temperature conditions, light conditions, winged perianth, salt concentrations, water stress, and burial depths on the seed germination or seedling emergence of S. collina. The results showed that S. collina produced two different types of fruits/seeds that significantly differed in seed size, seed color, external structure, and germination/dormancy behavior. The type A seeds (green seeds) were nondormant, and the germination percentage was >96% at all alternating day/night temperatures and light conditions; whereas type B seeds (yellow seeds) exhibited dormancy characteristics and poor germination (≤1%). Moreover, the winged perianth did not inhibit the germination of S. collina green seeds. The germination of green seeds declined rapidly when NaCl concentration exceeded 100 mM, and only 2.22% germination was observed at 600 mM NaCl. About 62.00% of green seeds germinated at −0.6 MPa, and 8.00% germination was obtained at −1.2 MPa. The seedling emergence declined with an increase of burial depth, and decreased sharply when the burial depth exceeded 1.0 cm. Only 8.33% seedling emergence occurred at a burial depth of 4.0 cm. The results gathered from present study will help to illustrate the ecological adaptation strategy of S. collina and indicate that shallow tillage can effectively minimize the seedling emergence of S. collina.

Unraveling the influence of environmental factors on fireweed (Senecio madagascariensis) germination and its management implications

AbstractFireweed (Senecio madagascariensis Poir.) has invaded and colonized numerous habitats in the coastal areas of southeastern Australia and is a major weed in cultivated lands as well as in poorly grassed, neglected, and highly grazed pastures. To examine the seed germination ecology of two populations (Felton and Gatton) of S. madagascariensis, experiments were conducted in the laboratory and screen house. The germination of both populations increased as the alternating temperatures increased from the coolest temperatures (15/5 C) to warmer temperatures (25/15 C). However, the highest temperature regime (35/25 C) resulted in the lowest germination rates. The Gatton population exhibited greater tolerance to higher temperatures, resulting in significantly higher germination (2.4 times) than the Felton population at the highest alternating temperature of 35/25 C. Compared with the Felton population, the Gatton population demonstrated higher tolerance to salt and water stress. In comparison to alternating light and dark periods (12 h each) (97% to 98%), the germination of both populations of S. madagascariensis was significantly reduced under complete darkness (24 h) (33% to 39%). A screen house seed burial depth experiment revealed similar emergence of S. madagascariensis seedlings between the populations. The maximum emergence (60%) was observed for seeds placed at the soil surface, followed by a dramatic decline in seedling emergence with an increase in depth. No seedlings emerged from a burial depth of 4 cm. With the addition of wheat (Triticum aestivum L.) crop residue to the soil surface at rates comparable to 4,000 to 8,000 kg ha−1, seedling emergence of S. madagascariensis decreased significantly. Information acquired from this study could be utilized to manage and develop effective weed management strategies for controlling S. madagascariensis in different agroecological conditions.

Vernalization affects the germination performance of the wetland endangered species Eleocharis carniolica

AbstractEleocharis carniolica W.D.J. Koch (Cyperaceae) is an endangered wetland spike rush mainly threatened by habitat loss and fragmentation. Understanding the germination ecology of this species is essential to perform successful conservation and restoration actions. In this study, we investigated the effect of vernalization (i.e. cold stratification), gibberellic acid (GA3) and chemical scarification on seed germination of E. carniolica from wild populations in northern Italy. The results showed that vernalization (i.e. 8-weeks at 4 °C) significantly improved germination probability, speed, and uniformity compared to non-stratified seeds. Gibberellic acid treatment alone or in combination with vernalization did not show a significant improvement in germination. Chemical scarification using sodium hypochlorite increased germination probability, with 8 h of scarification showing the highest success rate. However, 24-h scarification had a negative impact on germination. Overall, vernalization was found to be the most effective method to enhance germination in E. carniolica. These findings provide valuable insights into the seed germination ecology of this endangered species, aiding in its exsitu conservation, propagation, and in-situ restoration efforts. Moreover, they have important implications on future germination dynamics of this endangered species, especially with predicted climate change scenarios.

Herbicide response and germination behavior of two goosegrass (Eleusine indica) populations in the Australian environment

AbstractGoosegrass [Eleusine indica (L.) Gaertn.] is one of the most problematic grassy weeds in the world. It is considered to be an important weed in summer fallows and crops grown in the eastern region of Australia. To examine the seed germination ecology of two populations (Gatton and Ingham) of E. indica and their response to postemergence herbicides in Australian conditions, experiments were carried out in the laboratory and screenhouse. Seedling survival, spike production, and plant biomass of both E. indica populations declined markedly with the application of postemergence herbicides such as butroxydim, clethodim, glufosinate, haloxyfop, and propaquizafop, whereas the application of paraquat failed to control the Ingham population. A dose–response study verified the presence of paraquat resistance in the Ingham population. In this regard, it was observed that the paraquat doses required to achieve a 50% reduction in survival and plant biomass were 27 and 21 times greater in the Ingham population compared to the Gatton population, respectively. Higher alternating temperatures (35/25 and 30/20 C) resulted in greater germination of both populations than lower alternating temperatures (20/10 and 25/15 C). At 20/10 C, the Ingham population failed to germinate; however, about 15% germination in the Gatton population was observed. At the lowest alternate temperature range (15/5 C), neither population germinated. The germination of both populations of E. indica was severely reduced under completely dark conditions compared with the alternating light/dark period. Germination was more tolerant of salt and water stress in the Ingham population compared with the Gatton population. Eleusine indica seedling emergence was comparable among populations, and the greatest emergence (83%) was observed for seeds buried at a depth of 2 cm but then declined dramatically, and no seedlings emerged from an 8-cm burial depth. The information acquired from this study could be used in developing effective management strategies for E. indica.

Spider Plant (Cleome gynandra L.): An Emerging Weed in the Sweet Corn–Brassica Cropping System

Spider plant (Cleome gynandra L.) is an emerging noxious weed, affecting cultivated vegetables in Queensland, Australia. It is a prolific seed producer, forming large seedbanks with variable seedling emergence. A study was carried out to investigate the seed biology of spider plant, focusing on its seed germination ecology, viz., influence of temperatures, illumination conditions, medium salinity, pH, substrate moisture, burial depth, and after-ripening. Freshly harvested seeds were negatively photoblastic and had combinational dormancy. Improved germination was obtained by physical scarification followed by soaking for 16 h, by dry storage for over 6 months, and by the imbibition of gibberellic acid. Maximum germination percentages of 70 to 80% were recorded under constant darkness at alternating day/night temperatures of 20/30 °C, or with 18 to 27 °C constant temperatures. Spider plant showed a broad tolerance to pH but only moderate salt and moisture stress tolerance, since only 42 and 26% germination were observed with 60 mM NaCl and at −0.40 MPa, respectively. Seeds placed on the soil surface did not germinate, however, at a burial depth of 1.0 to 1.5 cm, which resulted in ca. 80% seedling emergence. These findings will assist land managers to predict seasonal emergence and will aid in deploying management approaches to control this weed.

Germination ecology and growth phenology of cowvine (Ipomoea lonchophylla) as influenced by environmental parameters

AbstractCowvine (Ipomoea lonchophylla J.M. Black) is a native and widely spread summer broadleaf weed in Australia. It contains glycoresins, which are toxic to livestock. However, limited information is available on seed germination ecology and growth phenology of this species. A series of experiments were conducted to determine the response of I. lonchophylla to different environmental conditions. Results showed that the primary dormancy exhibited by I. lonchophylla is due to the physical impediment of the hard seed coat. The seed germination percentage was the highest at the constant temperature of 27 C and alternating temperatures of 35/25 C. Germination of I. lonchophylla was not stimulated by light, suggesting that this species is non-photoblastic. Ipomoea lonchophylla germination was intolerant of a medium to high level of salt stress, and germination was completely inhibited at 250 mM NaCl. The emergence of I. lonchophylla was not restricted by seeding depth up to 8 cm, but only 5% emergence was recorded when seeds were planted at a 16-cm depth. The germination percentage was also drastically reduced by 90% to 100% after exposure to either 3 mo in silage, 48-h digestion in steers, or silage plus digestion treatments. The growth and reproductive phenology of I. lonchophylla was affected by emergence time. Plants that emerged in late spring (November 15) were able to produce more berries per plant than those that emerged in midsummer (January 15) in southern New South Wales. Information gained in our study concerning high soil salinity, ensiling, and digestion will help to develop more sustainable and effective integrated weed management strategies for controlling and reducing the spread of this weed.

Retraction: Seed germination ecology of Conyza sumatrensis populations stemming from different habitats and implications for management.

Retraction: Seed germination ecology of Conyza sumatrensis populations stemming from different habitats and implications for management.

Effects of seed germination ecology and its cleaning stage on in vitro seed germination performance of two indigenous bamboo species in Ethiopia

Effects of seed germination ecology and its cleaning stage on in vitro seed germination performance of two indigenous bamboo species in Ethiopia

Seed Germination Ecology of Chenopodium album and Chenopodium murale.

Chenopodium album L. and Chenopodium murale L. are two principal weed species, causing substantial damage to numerous winter crops across the globe. For sustainable and resource-efficient management strategies, it is important to understand weeds' germination behaviour under diverse conditions. For the germination investigations, seeds of both species were incubated for 15 days under different temperatures (10-30 °C), salinity (0-260 mM NaCl), osmotic stress (0-1 MPa), pH (4-10), and heating magnitudes (50-200 °C). The results indicate that the germination rates of C. album and C. murale were 54-95% and 63-97%, respectively, under a temperature range of 10 to 30 °C. The salinity levels for a 50% reduction in the maximum germination (GR50) for C. album and C. murale were 139.9 and 146.3 mM NaCl, respectively. Regarding osmotic stress levels, the GR50 values for C. album and C. murale were 0.44 and 0.43 MPa, respectively. The two species showed >95% germination with exposure to an initial temperature of 75 °C for 5 min; however, seeds exposed to 100 °C and higher temperatures did not show any germination. Furthermore, a drastic reduction in germination was observed when the pH was less than 6.0 and greater than 8.0. The study generated information on the germination biology of two major weed species under diverse ecological scenarios, which may be useful in developing efficient weed management tactics for similar species in future agri-food systems.

Seed-Germination Ecology of Vicia villosa Roth, a Cover Crop in Orchards

Vicia villosa Roth is an annual cover crop that is widely grown in orchards in China. Information on seed ecology is valuable as it helps famers to plant cover crops and manage other weed species in agricultural practice; however, information on V. villosa seed-germination ecology is limited. Thus, this study investigated the seed germination and seedling emergence of V. villosa under various temperatures, photoperiods, levels of salt stress, pH, levels of osmotic stress, and burial depths. The results showed that the germination values of the V. villosa seeds were greater than 93% at the constant temperature range of 5–30 °C and fluctuating temperatures of 5/15 °C–20/30 °C; in particular, the germination of the seeds peaked 20 °C and 15/25 °C, with germination values of 95% and 94.5%, respectively. Light was not necessary for the V. villosa seeds’ germination. When the pH was in the range of 5–10, the germination values of the V. villosa seeds fluctuated between 85% and 94%, and obvious inhibition of germination was observed at pH = 4, with a germination value of 15%. The Vicia villosa seeds exhibited obvious salt tolerance, and the seed-germination value was still greater than 50% when the salt concentration reached 280 mM. The seeds were relatively sensitive to osmotic stress, and the germination value was lower than 50% when the osmotic potential was −0.5 MPa. In addition, the germination value of the seeds peaked when the seeds were 1–2 cm underneath the ground; in particular, the seeds still germinated and emerged when the seeds were buried in soli at a depth of 10 cm. These results confirmed that V. villosa, as a cover crop, has considerable potential to be planted and grown in orchards in China and, furthermore, that it may contribute to early weed management in fields, supporting the establishment of V. villosa populations.

Seed germination ecology of hood canarygrass (Phalaris paradoxa L.) and herbicide options for its control

Hood canarygrass (Phalaris paradoxa L.) is a problematic weed in winter crops of Australia. Experiments were conducted to determine the effects of environmental factors on seed germination of P. paradoxa and wheat (Triticum aestivum L.) and herbicide options for P. paradoxa control. Results revealed that P. paradoxa had higher germination (> 89%) at a temperature range from 15/5 ℃ to 25/15 ℃ [day/night (12 h/12 h] compared with 30/20 ℃ and 35/25 ℃. At a temperature regime of 30/20 ℃, P. paradoxa had 1% germination; however, wheat at this temperature range resulted in 79% germination. Exposure of seeds of P. paradoxa to > 150 ℃ pretreatment (radiant heat for 5 min) resulted in no germination. These results suggest that infestation of P. paradoxa could be reduced by residue burning or by planting wheat crops early in the season when the temperature is relatively high. At a water potential of -0.8 MPa, seed germination of P. paradoxa and wheat was 75 and 96%, respectively. Similarly, at the highest salt concentration (200 mM sodium chloride), seed germination of P. paradoxa and wheat was 73 and 79%, respectively. These observations suggest that like wheat, P. paradoxa is also highly tolerant to water and salt stress conditions, therefore, it could invade the agro-ecosystem under water and salt stress situations. Germination of P. paradoxa was found to be low (10%) on the soil surface, suggesting that no-till systems could inhibit the germination of P. paradoxa. Pre-emergent (PRE) herbicides, namely cinmethylin, pyroxasulfone, and trifluralin, provided 100% control of P. paradoxa; however, in the presence of 2 t ha−1 of residue cover, pyroxasulfone provided better control of P. paradoxa compared with other herbicides. Post-emergent (POST) herbicides clethodim, haloxyfop, and paraquat provided excellent control of P. paradoxa, even if the plant size was large (10-leaf stage). Knowledge generated from this study will help in strengthening the integrated management of P. paradoxa.

Seed germination ecology of common bladderwort (Utricularia vulgaris L.)

Generative reproduction of the carnivorous aquatic plant Utricularia vulgaris (Lentibulariaceae) from seeds may be a critical process in the recovery of natural populations following temporary drying of habitat, and in the colonisation of new potential sites through dispersal of seeds by water birds. However, little is presently known about the seed ecology and germination biology of this species. We tested the germination response of seeds under various temperature and seed storage regimes, to examine the processes required for seed dormancy alleviation and the effects of different germination solution and temperature on germination probability. Seeds likely possess non-deep simple morphophysiological dormancy alleviated by warm stratification. Highest germination success was recorded for warm-stratified seeds and seeds exposed to ethylene. Seeds were photophilous, with germination more successful at 21 °C than at 25 °C and greatest in slightly alkaline (pH 8) germination solution containing KHCO3, CaCl2 and MgSO4 mimicking the mesotrophic humic waters in which the species naturally occurs. In the alkaline solution, 97 % of seeds rose to the surface prior to germination. In natural habitats, this effect may facilitate seedlings reaching the warmer and irradiated water surface. As seed germination success appears linked to light availability, water chemistry, and seed position in the water column, careful management and ecological restoration of remnant habitats harbouring this species may need to ensure positive conservation outcomes.

Seed Germination Ecology of Semiparasitic Weed Pedicularis kansuensis in Alpine Grasslands.

The semiparasitic weed Pedicularis kansuensis Maxim. has rapidly spread in the alpine grasslands of northern China over the past twenty years and has caused serious ecological problems. In order to effectively halt the spread of this weed, a thorough understanding of the dormancy type and the seed-germination ecology of P. kansuensis is required. We have conducted a series of experiments to investigate the effects of plant growth regulators (gibberellin (GA3) and strigolactone synthesis (GR24)), as well as different abiotic (temperature, light, cold stratification, and drought) and biotic (aqueous extracts of three native dominant plants) factors on the seed-germination characteristics of P. kansuensis. The seed-germination percentages ranged from 2% to 62% at all of the temperatures that were examined, with the highest occurring at 25/10 °C. The light conditions did not significantly affect the germination percentage. The seed germination was greatly improved after two to eight weeks of cold stratification. The seed germination decreased dramatically with an increasing polyethylene glycol (PEG-6000) concentration, from 55% to 0%, under 10% and 20% PEG-6000. The seed germination was improved at a proper concentration of GA3, GR24, and the aqueous extracts of Festuca ovina L., Stipa purpurea L., and Leymus secalinus (Georgi) Tzvel. Furthermore, in the pot experiment, the seedling emergence of P. kansuensis was also improved by the cultivation of these three dominant grasses. These findings indicate that the dormancy type of P. kansuensis seeds is non-deep physiological dormancy, and such findings will help in paving the way for the creation of effective weed management strategies, based on a thorough knowledge of germination ecology.

Seed germination ecology of leucaena (Leucaena leucocephala) as influenced by various environmental parameters

AbstractLeucaena [Leucaena leucocephala (Lam.) de Wit] is a perennial weed in more than 25 countries, including Australia. Knowledge regarding the seed biology of L. leucocephala could help in making weed management decisions. Experiments were conducted to study the effect of hot water (scarification), alternating temperatures, heat stress, salt stress, water stress, and burial depth on seed germination of two populations of L. leucocephala collected from Toowoomba and Gatton, Australia. The optimum duration of hot water treatment to break the hard seed coat dormancy was 2 min for both populations. The highest germination (92% to 98%) was recorded at 35/25 C for both populations, and similar germination occurred at 30/20 C. The Toowoomba population recorded greater germination at low temperature (15/5 to 25/15 C) than the Gatton population. Additionally, the Gatton population had higher germination than the Toowoomba population after 5 min of exposure to temperatures of up to 100 C, suggesting that the Gatton population may be more tolerant to heat stress. Germination was completely inhibited at pretreatment (5 min) temperatures of 150 to 250 C. The Toowoomba population recorded 17% greater germination than the Gatton population at a high salt concentration (160 mM NaCl), indicating its greater salt tolerance. At low moisture stress (−0.1 and −0.2 MPa), higher germination was observed in the Toowoomba population than in the Gatton population, whereas germination was similar for both populations at higher water stress levels (−0.4 MPa or lower). Germination was similar for both populations at shallow depths (0 and 1 cm) but higher emergence was recorded for the Toowoomba population at 2 to 8 cm than the Gatton population. Differential germination behaviors of both populations suggest that they adapted differently in their respective local environments. Knowledge gained from this study will help in formulating integrated management practices for L. leucocephala.

Seed size dimorphism in Hyptis suaveolens aids in differentiation of the germination niche.

Seed germination characteristics help predict the degree of invasive success of a species based on capacity of the seeds to germinate and recruit into novel habitats. Hyptis suaveolens (L.) Poit. (Bush mint, Pignut; Lamiaceae) is an invasive plant that is spreading throughout tropical and subtropical regions worldwide. We conducted a study to understand the role of seed size dimorphism in differentiation of germination niche in H. suaveolens. We subjected small and large seeds to varying environmental conditions of temperature (°C), photoperiod (light/dark), salt (NaCl; mM), pH, osmotic potential (MPa), different soil types and ratios (clay:sand) and burial depth (cm). Different germination indices were calculated and their interaction with seed dimorphism studied. There was a significant interaction (P < 0.001) between germination indices and seed dimorphism throughout the treatments. Large seeds had higher germination percentage and rate, indicating higher germination capacity. In addition, these displayed more asynchronous germination under various environments. Small seeds, on the other hand, required a longer germination time as compared to large seeds, indicating slower germination. Differential responses of the two seed morphs to varying environmental conditions, therefore, help H. suaveolens to differentiate its germination niche and establish in heterogeneous environments. These findings will help in devising appropriate management and eradication strategies based on germination ecology of seeds.

Seed germination ecology of Conyza sumatrensis populations stemming from different habitats and implications for management.

Conyza sumatrensis (Retz.) E. H. Walker is an obnoxious weed, emerging as an invasive species globally. Seed germination biology of four populations of the species stemming from arid, semi-arid, temperate, and humid regions was determined in this study. Seed germination was recorded under six different environmental cues (i.e., light/dark periods, constant and alternating day and night temperatures, pH, salinity, and osmotic potential levels) in separate experiment for each cue. Populations were main factor, whereas levels of each environmental cue were considered as sub-factor. The impact of seed burial depths on seedling emergence was inferred in a greenhouse pot experiment. Seed germination was recorded daily and four germination indices, i.e., seed germination percentage, mean germination time, time to reach 50% germination, and mean daily germination were computed. Tested populations and levels of different environmental cues had significant impact on various seed germination indices. Overall, seeds stemming from arid and semi-arid regions had higher seed germination potential under stressful and benign environmental conditions compared to temperate and humid populations. Seed of all populations required a definite light period for germination and 12 hours alternating light and dark period resulted in the highest seed germination. Seed germination of all populations occurred under 5–30°C constant and all tested alternate day and night temperatures. However, the highest seed germination was recorded under 20°C. Seeds of arid and semi-arid populations exhibited higher germination under increased temperature, salinity and osmotic potential levels indicating that maternal environment strongly affected germination traits of the tested populations. The highest seed germination of the tested populations was noted under neutral pH, while higher and lower pH than neutral had negative impact on seed germination. Arid and semi-arid populations exhibited higher seed germination under increased pH compared to temperate and humid populations. Seed burial depth had a significant effect on the seedling emergence of all tested populations. An initial increase was noted in seedling emergence percentage with increasing soil depth. However, a steep decline was recorded after 2 cm seed burial depth. These results indicate that maternal environment strongly mediates germination traits of different populations. Lower emergence from >4 cm seed burial depth warrants that deep burial of seeds and subsequent zero or minimum soil disturbance could aid the management of the species in agricultural habitats. However, management strategies should be developed for other habitats to halt the spread of the species.

Using seminatural and simulated habitats for seed germination ecology of banana wild relatives.

Ecologically meaningful seed germination experiments are constrained by access to seeds and relevant environments for testing at the same time. This is particularly the case when research is carried out far from the native area of the studied species.Here, we demonstrate an alternative—the use of glasshouses in botanic gardens as simulated‐natural habitats to extend the ecological interpretation of germination studies. Our focal taxa were banana crop wild relatives (Musa acuminata subsp. burmannica, Musa acuminata subsp. siamea, and Musa balbisiana), native to tropical and subtropical South‐East Asia. Tests were carried out in Belgium, where we performed germination tests in relation to foliage‐shading/exposure to solar radiation and seed burial depth, as well as seed survival and dormancy release in the soil. We calibrated the interpretation of these studies by also conducting an experiment in a seminatural habitat in a species native range (M. balbisiana—Los Baños, the Philippines), where we tested germination responses to exposure to sun/shade. Using temperature data loggers, we determined temperature dynamics suitable for germination in both these settings.In these seminatural and simulated‐natural habitats, seeds germinated in response to exposure to direct solar radiation. Seed burial depth had a significant but marginal effect by comparison, even when seeds were buried to 7 cm in the soil. Temperatures at sun‐exposed compared with shaded environments differed by only a few degrees Celsius. Maximum temperature of the period prior to germination was the most significant contributor to germination responses and germination increased linearly above a threshold of 23℃ to the maximum temperature in the soil (in simulated‐natural habitats) of 35℃.Glasshouses can provide useful environments to aid interpretation of seed germination responses to environmental niches.

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

AbstractWild 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 populations (Queensland [Qld] population: tropical region; and Victoria [Vic] population: temperate region) 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 controls. At 40, 80, and 160 mM sodium chloride, germination was lower for the Qld population 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 suggest 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.

Seed germination ecology of Sumatran fleabane (Conyza sumatrensis) in relations to various environmental parameters

AbstractSumatran fleabane [Conyza sumatrensis (Retz.) Walker] is an emerging weed in the Australian cropping region. Populations resistant to glyphosate have evolved in Australia, creating the demand for information regarding the seed germination ecology of glyphosate-resistant (R) and glyphosate-susceptible (S) populations of C. sumatrensis. A study was conducted to examine the effects of temperature, light intensity, salt stress, osmotic stress, and burial depth on the germination and emergence of two populations (R and S) of C. sumatrensis. Both populations were able to germinate over a wide range of alternating day/night temperatures (15/5 to 35/25 C). In light/dark conditions, the R population had higher germination than the S population at 20/10 and 35/25 C. In the dark, the R population had higher germination than the S population at 25/15 C. In the dark, germination was inhibited at 30/20 C and above. Averaged over populations, seed germination of C. sumatrensis was reduced by 97% at zero light intensity (completely dark conditions) compared with full light intensity. Seed germination of C. sumatrensis was reduced by 17% and 85% at osmotic potentials of −0.4, and −0.8 MPa, respectively, compared with the control treatment. The R population had lower germination (57%) than the S population (72%) at a sodium chloride concentration of 80 mM. Seed germination was highest on the soil surface and emergence was reduced by 87% and 90% at burial depths of 0.5 and 1.0 cm, respectively. Knowledge gained from this study suggests that a shallow-tillage operation to bury weed seeds in conventional tillage systems and retention of high residue cover on the soil surface in zero-till systems may inhibit the germination of C. sumatrensis. This study also warrants that the R population may have a greater risk of invasion over a greater part of a year due to germination over a broader temperature range.

Correction: Seed germination ecology of Conyza stricta Willd. and implications for management

[This corrects the article DOI: 10.1371/journal.pone.0244059.].