Factors affecting seed germination of feather fingergrass (Chloris virgata)
- Fernando, Nimesha, Humphries, Talia, Florentine, Singarayer, Chauhan, Bhagirath
- Authors: Fernando, Nimesha , Humphries, Talia , Florentine, Singarayer , Chauhan, Bhagirath
- Date: 2016
- Type: Text , Journal article
- Relation: Weed Science Vol. 64, no. 4 (2016), p. 605-612
- Full Text: false
- Reviewed:
- Description: Laboratory experiments were carried out to determine the effect of several environmental factors on seed germination of feather fingergrass, one of the most significant emerging weeds in warm regions of the world. Seed germination occurred over a broad range of temperatures (17/7, 25/10, and 30/20 C), but germination being highest at alternating temperatures of 30/20 C under both 12 h light/12 h dark and 24 h dark conditions. Although seed germination was favored by light, some seeds were capable of germinating in the dark. Increasing salt stress decreased seed germination until complete inhibition was reached at 250-mM sodium chloride. Germination decreased from 64 to 0.7% as osmotic potential decreased from 0 to -0.4 MPa, and was completely inhibited at -0.6 MPa. Higher seed germination (>73%) was observed in the range of pH 6.4 to 8 than the other tested pH levels. Heat shock had a significant effect on seed germination. Germination of seeds placed at 130 C for 5 min was completely inhibited for both dry and presoaked seeds. The results of this study will help to develop protocols for managing feather fingergrass, and to thus avoid its establishment as a troublesome weed in economically important cropping regions.
- Humphries, Talia, Graz, Friedrich, Florentine, Singarayer
- Authors: Humphries, Talia , Graz, Friedrich , Florentine, Singarayer
- Date: 2018
- Type: Text , Journal article
- Relation: Rangeland Journal Vol. 40, no. 6 (2018), p. 583-590
- Full Text: false
- Reviewed:
- Description: 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 12 h light and 12 h 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 3 min. Burial depth had a significant effect on seedling emergence, with a burial depth of 0.5 cm reducing the germination by
Environmental factors effecting the germination and seedling emergence of two populations of an aggressive agricultural weed; Nassella trichotoma
- Humphries, Talia, Chauhan, Bhagirath, Florentine, Singarayer
- Authors: Humphries, Talia , Chauhan, Bhagirath , Florentine, Singarayer
- Date: 2018
- Type: Text , Journal article
- Relation: PLoS ONE Vol. 13, no. 7 (2018), p. 1-25
- Full Text:
- Reviewed:
- Description: Nassella trichotoma (Nees) Hack. ex Arechav. (Serrated tussock) is an aggressive globally significant weed to agricultural and natural ecosystems. Herbicide resistant populations of this C3 perennial weed have emerged, increasing the need for effective wide-scale cultural control strategies. A thorough seed ecology study on two spatially distinct populations of N. trichotoma was conducted on this weed to identify differences in important environmental factors (drought, salinity, alternating temperature, photoperiod, burial depth, soil pH, artificial seed aging, and radiant heat) which influence seed dormancy. Seeds were collected from two spatially distinct populations; Gnarwarre (38 O 9’ 8.892’’ S, 144 O 7’ 38.784’’ E) and Ingliston (37O 40’ 4.44’’ S, 144 O 18’ 39.24’’ E) in December 2016 and February 2017, respectively. Twenty sterilized seeds were placed into Petri dishes lined with a single Whatman® No. 10 filter paper dampened with the relevant treatments solution and then incubated under the identified optimal alternating temperature and photoperiod regime of 25C/ 15C (light/dark, 12h/12h). For the burial depth treatment, 20 seeds were placed into plastic containers (10cm in diameter and 6cm in depth) and buried to the relevant depth in sterilized soil. All trials were monitored for 30 days and germination was indicated by 5mm exposure of the radicle and emergence was indicated by the exposure of the cotyledon. Each treatment had three replicates for each population, and each treatment was repeated to give a total of six replicates per treatment, per population. Nassella trichotoma was identified to be non-photoblastic, with germination (%) being similar under alternating light and dark and complete darkness conditions. With an increase of osmotic potential and salinity, a significant decline in germination was observed. There was no effect of pH on germination. Exposure to a radiant heat of 120C for 9 minutes resulted in the lowest germination in the Ingliston population (33%) and the Gnarwarre population (60%). In the burial depth treatment, the Ingliston population and the Gnarwarre population had highest emergence of 75% and 80%, respectively at a depth of 1cm. Variation between the two populations was observed for the burial depth treatments; Gnarwarre had greater emergence than Ingliston from the 4cm burial depth, while Ingliston had greater emergence at the soil surface than Gnarwarre. The Gnarwarre population had greater overall germination than Ingliston, which could be attributed to the greater seed mass (0.86mg compared to 0.76mg, respectively). This study identifies that spatial variations in N. trichotoma’s seed ecology are present between spatially distinct populations.
- Authors: Humphries, Talia , Chauhan, Bhagirath , Florentine, Singarayer
- Date: 2018
- Type: Text , Journal article
- Relation: PLoS ONE Vol. 13, no. 7 (2018), p. 1-25
- Full Text:
- Reviewed:
- Description: Nassella trichotoma (Nees) Hack. ex Arechav. (Serrated tussock) is an aggressive globally significant weed to agricultural and natural ecosystems. Herbicide resistant populations of this C3 perennial weed have emerged, increasing the need for effective wide-scale cultural control strategies. A thorough seed ecology study on two spatially distinct populations of N. trichotoma was conducted on this weed to identify differences in important environmental factors (drought, salinity, alternating temperature, photoperiod, burial depth, soil pH, artificial seed aging, and radiant heat) which influence seed dormancy. Seeds were collected from two spatially distinct populations; Gnarwarre (38 O 9’ 8.892’’ S, 144 O 7’ 38.784’’ E) and Ingliston (37O 40’ 4.44’’ S, 144 O 18’ 39.24’’ E) in December 2016 and February 2017, respectively. Twenty sterilized seeds were placed into Petri dishes lined with a single Whatman® No. 10 filter paper dampened with the relevant treatments solution and then incubated under the identified optimal alternating temperature and photoperiod regime of 25C/ 15C (light/dark, 12h/12h). For the burial depth treatment, 20 seeds were placed into plastic containers (10cm in diameter and 6cm in depth) and buried to the relevant depth in sterilized soil. All trials were monitored for 30 days and germination was indicated by 5mm exposure of the radicle and emergence was indicated by the exposure of the cotyledon. Each treatment had three replicates for each population, and each treatment was repeated to give a total of six replicates per treatment, per population. Nassella trichotoma was identified to be non-photoblastic, with germination (%) being similar under alternating light and dark and complete darkness conditions. With an increase of osmotic potential and salinity, a significant decline in germination was observed. There was no effect of pH on germination. Exposure to a radiant heat of 120C for 9 minutes resulted in the lowest germination in the Ingliston population (33%) and the Gnarwarre population (60%). In the burial depth treatment, the Ingliston population and the Gnarwarre population had highest emergence of 75% and 80%, respectively at a depth of 1cm. Variation between the two populations was observed for the burial depth treatments; Gnarwarre had greater emergence than Ingliston from the 4cm burial depth, while Ingliston had greater emergence at the soil surface than Gnarwarre. The Gnarwarre population had greater overall germination than Ingliston, which could be attributed to the greater seed mass (0.86mg compared to 0.76mg, respectively). This study identifies that spatial variations in N. trichotoma’s seed ecology are present between spatially distinct populations.
Cultivation of low tetrahydrocannabinol (THC) Cannabis sativa L. cultivation in Victoria, Australia: Do we know enough?
- Humphries, Talia, Florentine, Singarayer
- Authors: Humphries, Talia , Florentine, Singarayer
- Date: 2019
- Type: Text , Journal article
- Relation: Australian Journal of Crop Science Vol. 13, no. 6 (2019), p. 911-919
- Full Text:
- Reviewed:
- Description: Late 2017, the ban on the cultivation and consumption of low tetrahydrocannabinol (THC) Cannabis sativa L. in Victoria, was lifted by the Federal Government of Australia. Its legalization presents the opportunity for Victoria to become a leading producer and distributer of these economically valuable hemp products. However, as a novel crop to Victoria, there is little information available for obtaining economically viable yields. Therefore, the objectives of this review were to firstly, develop an understanding of the environmental requirements shared by C. sativa cultivars, and what conditions promote fibre and grain yields. Secondly, it seeks to identify what farming practices have been conducted throughout Europe, Canada and China, and to explore whether these practices could be adapted to Victoria. Thirdly, the review will assist in making recommendations regarding which cultivars would be 'potential' candidates for commencing trials under Victorian climates so to find out the varieties that can provide high yields for fibre, grain and dual-purpose production. This review notes that Victoria shares a similar climate to central Europe, and has an ideal climate for the development of a successful hemp industry, as it has suitable lengths of daylight throughout spring and summer months and meets the precipitation requirements. This review has thus strongly suggested that the properties and attributes of European varieties of C. sativa should be further researched for site-specific cultivation in Victoria for fibre, grain and dual-purpose production in order to maximise harvest yields. © 2007-2019 Southern Cross Publishing-Australia.
- Authors: Humphries, Talia , Florentine, Singarayer
- Date: 2019
- Type: Text , Journal article
- Relation: Australian Journal of Crop Science Vol. 13, no. 6 (2019), p. 911-919
- Full Text:
- Reviewed:
- Description: Late 2017, the ban on the cultivation and consumption of low tetrahydrocannabinol (THC) Cannabis sativa L. in Victoria, was lifted by the Federal Government of Australia. Its legalization presents the opportunity for Victoria to become a leading producer and distributer of these economically valuable hemp products. However, as a novel crop to Victoria, there is little information available for obtaining economically viable yields. Therefore, the objectives of this review were to firstly, develop an understanding of the environmental requirements shared by C. sativa cultivars, and what conditions promote fibre and grain yields. Secondly, it seeks to identify what farming practices have been conducted throughout Europe, Canada and China, and to explore whether these practices could be adapted to Victoria. Thirdly, the review will assist in making recommendations regarding which cultivars would be 'potential' candidates for commencing trials under Victorian climates so to find out the varieties that can provide high yields for fibre, grain and dual-purpose production. This review notes that Victoria shares a similar climate to central Europe, and has an ideal climate for the development of a successful hemp industry, as it has suitable lengths of daylight throughout spring and summer months and meets the precipitation requirements. This review has thus strongly suggested that the properties and attributes of European varieties of C. sativa should be further researched for site-specific cultivation in Victoria for fibre, grain and dual-purpose production in order to maximise harvest yields. © 2007-2019 Southern Cross Publishing-Australia.
Erigeron bonariensis, erigeron canadensis, and erigeron sumatrensis
- Florentine, Singarayer, Humphries, Talia, Chauhan, Bhagirath
- Authors: Florentine, Singarayer , Humphries, Talia , Chauhan, Bhagirath
- Date: 2021
- Type: Text , Book chapter
- Relation: Biology and Management of Problematic Crop Weed Species, 1st Edition Chapter 7 p. 131-149
- Full Text: false
- Reviewed:
- Description: The global human population is expected to reach 8-10 billion by 2050. According to the United Nations, this expansion in population is expected to increase food demands by double the current demand by 2050. Consequently, existing food production systems will come under significant strain. Exacerbating this food production problem is that agronomic weed species across the globe are already causing significant impacts on essential grain yields. Over the past decades, to address weed infestations, farmers have been using range of herbicides. However, overuse of these chemicals has resulted in many weed species mutating to a more resistant form. To implement a successful integrated weed management approach in the future, it will be essential to document the changes in ecology and biology of significant weed species. This chapter focuses on the three most globally significant weeds: Erigeron bonariensis, Erigeron canadensis, and Erigeron sumatrensis, summarizing their current global distribution, seed ecology, impacts, control strategies, as well as current herbicide resistance. These three species are causing significant impacts on important agricultural products including corn, soybean, cotton, wheat, chickpea, sorghum, orchards, and vineyards. Addressing the problem of high levels of herbicide resistance within the Erigeron species has been attempted through various solutions, including novel herbicide mixtures and application timing. Targeting these species in their earlier growth stage with herbicide combinations can greatly improve the success of integrated treatments, broadening the options for suitable approaches such as the use of zero or no-till systems. Given that, these species have innate traits including (1) high seed production, (2) low levels of seed dormancy, (3) high emergence rates, (4) efficient seed dispersal mechanisms, and (5) a highly competitive nature. These advantages, coupled with their ability to withstand a range of climatic conditions and their increasing herbicide-resistant biotypes, make them a serious agricultural weed species across the globe. In this chapter, we have synthesized the characteristic biological features and the effectiveness of various control options. Very limited information is available on the ecology and biology of E. sumatrensis. We have, nevertheless, harvested a significant amount of useful information which may assist farmers to effectively develop integrated agricultural management practices to reduce the impacts of these three species in their productive lands. © 2021 Elsevier Inc. All rights reserved.
Initiating temperate grassland restoration by controlling the dominant weed species; a case study with Nassella trichotoma
- Authors: Humphries, Talia
- Date: 2022
- Type: Text , Thesis , PhD
- Full Text:
- Description: Temperate grasslands are globally important biomes, in that they (i) provide habitat for a wide diversity of species, (ii) sequester large stocks of carbon, and (iii) provide forage for important pollinators (Chapter 1). These ecosystems often fall within highly fertile areas, and consequently humans have come to depend on them to provide high quality forage for grazing livestock and land for agricultural development. Temperate grasslands are considered to be critically endangered on a global scale. The grazing industry relies upon healthy and productive grasslands for the production of a substantial proportion of human food products, however, when these systems incorporate unsustainable land-management practises, such as over-grazing and continual fertilisation with inorganic matter, has resulted in a significant decline in important native grass species. This has resulted in encroachment of unpalatable, noxious plants, which decrease the quality of available forage. One such noxious weed species, Nassella trichotoma, known commonly as serrated tussock, is having a significance impact on the constitution of temperate grasslands and grazing systems, globally, due to its unpalatability and competitive growth form. In order to return temperate grasslands to a fully-functional and a high-quality forage state, human intervention in terms of ecosystem restoration is required. The control of noxious species, together with the reintroduction and establishment of native species, is a critical step for restoration efforts with the return of native plant diversity, and the re-establishment of ecosystem services, such as habitat for higher trophic levels. This thesis reviews and overlaps the scientific disciplines of ecosystem restoration (Chapter 2), weed science relating to N. trichotoma (Chapter 3), and environmental management in order to provide solutions for controlling N. trichotoma in non-native grassland communities (Chapter 4). The effect of direct herbicide application, soil tillage, grazing exclusion, fire, and broadcasting native seeds for the control of this dominant weeds in a total of 13 different combinations is investigated. The experimental plots were surveyed over a four-year period and soil cores were collected over a three-year period to survey the seedbank density. It was found that the inclusion of fire significantly increased the establishment of the native broadcast species. Also, without the integration of fire or tillage, N. trichotoma recovered, and consequently was observed to be the dominant species in the final sampling period. To support the findings of Chapter 4, research into the seed longevity and seedbank persistence of N. trichotoma was undertaken in Chapter 5. It was found that less than 10% of the seeds were observed to be viable after 12 months of burial in field. In addition to this, the longevity of the seeds was determined by rapidly ageing the seeds through exposure to high relative humidity and temperature. This process determined that N. trichotoma produces transient seedbanks, referring to those that persist for 12 months or less, and therefore the seedbank would be reliant on new seed input annually to remain a competitive threat. This implies that management control of new seed fall is essential to prevent the reestablishment of the seed bank. The seedbank persistence for N. trichotoma is complicated by disturbance events such as fire. To investigate this impact, four different collection years; 2016, 2017, 2018, and 2019 were subjected to increasing heat (80, 100, 120, or 140OC) and time of exposure (1, 3, 6 or 9 minutes) by placing them into a temperature-controlled oven for the given treatment. It was found that only the 140OC treatment was significant for killing N. trichotoma, as detailed in Chapter 6. High moisture content (95%) increased the seeds sensitivity to radiant heat, with all tested temperature effective for killing this species. The seedlings were not killed by the tested treatments. Management implications and recommendations for the control of N. trichotoma in temperate grasslands (Chapter 7) include; (i) the use of herbicide in Autumn to prevent seed set in the following summer, and (ii) in addition to initial herbicide, use, subsequent fire treatment and broadcasting native seeds appear to provide ongoing competition against N. trichotoma reestablishment in treated areas. Further, high fire intensities, where the soil is heated to 140OC or more, can kill N. trichotoma’s seedbank and prevent its recruitment. In all cases of treatment, monitoring recruitment from the seedbank is recommended for up to one year after treating a site. This thesis suggests that localised eradication of N. trichotoma is achievable in as little as three years if (i) above-ground plants are treated, (ii) seedling recruitment from the seedbank is managed intensely within the first year, (iii) high densities of native grass is established to provide competition, and (iv) the addition of new seed is prevented.
- Description: Doctor of Philosophy
- Authors: Humphries, Talia
- Date: 2022
- Type: Text , Thesis , PhD
- Full Text:
- Description: Temperate grasslands are globally important biomes, in that they (i) provide habitat for a wide diversity of species, (ii) sequester large stocks of carbon, and (iii) provide forage for important pollinators (Chapter 1). These ecosystems often fall within highly fertile areas, and consequently humans have come to depend on them to provide high quality forage for grazing livestock and land for agricultural development. Temperate grasslands are considered to be critically endangered on a global scale. The grazing industry relies upon healthy and productive grasslands for the production of a substantial proportion of human food products, however, when these systems incorporate unsustainable land-management practises, such as over-grazing and continual fertilisation with inorganic matter, has resulted in a significant decline in important native grass species. This has resulted in encroachment of unpalatable, noxious plants, which decrease the quality of available forage. One such noxious weed species, Nassella trichotoma, known commonly as serrated tussock, is having a significance impact on the constitution of temperate grasslands and grazing systems, globally, due to its unpalatability and competitive growth form. In order to return temperate grasslands to a fully-functional and a high-quality forage state, human intervention in terms of ecosystem restoration is required. The control of noxious species, together with the reintroduction and establishment of native species, is a critical step for restoration efforts with the return of native plant diversity, and the re-establishment of ecosystem services, such as habitat for higher trophic levels. This thesis reviews and overlaps the scientific disciplines of ecosystem restoration (Chapter 2), weed science relating to N. trichotoma (Chapter 3), and environmental management in order to provide solutions for controlling N. trichotoma in non-native grassland communities (Chapter 4). The effect of direct herbicide application, soil tillage, grazing exclusion, fire, and broadcasting native seeds for the control of this dominant weeds in a total of 13 different combinations is investigated. The experimental plots were surveyed over a four-year period and soil cores were collected over a three-year period to survey the seedbank density. It was found that the inclusion of fire significantly increased the establishment of the native broadcast species. Also, without the integration of fire or tillage, N. trichotoma recovered, and consequently was observed to be the dominant species in the final sampling period. To support the findings of Chapter 4, research into the seed longevity and seedbank persistence of N. trichotoma was undertaken in Chapter 5. It was found that less than 10% of the seeds were observed to be viable after 12 months of burial in field. In addition to this, the longevity of the seeds was determined by rapidly ageing the seeds through exposure to high relative humidity and temperature. This process determined that N. trichotoma produces transient seedbanks, referring to those that persist for 12 months or less, and therefore the seedbank would be reliant on new seed input annually to remain a competitive threat. This implies that management control of new seed fall is essential to prevent the reestablishment of the seed bank. The seedbank persistence for N. trichotoma is complicated by disturbance events such as fire. To investigate this impact, four different collection years; 2016, 2017, 2018, and 2019 were subjected to increasing heat (80, 100, 120, or 140OC) and time of exposure (1, 3, 6 or 9 minutes) by placing them into a temperature-controlled oven for the given treatment. It was found that only the 140OC treatment was significant for killing N. trichotoma, as detailed in Chapter 6. High moisture content (95%) increased the seeds sensitivity to radiant heat, with all tested temperature effective for killing this species. The seedlings were not killed by the tested treatments. Management implications and recommendations for the control of N. trichotoma in temperate grasslands (Chapter 7) include; (i) the use of herbicide in Autumn to prevent seed set in the following summer, and (ii) in addition to initial herbicide, use, subsequent fire treatment and broadcasting native seeds appear to provide ongoing competition against N. trichotoma reestablishment in treated areas. Further, high fire intensities, where the soil is heated to 140OC or more, can kill N. trichotoma’s seedbank and prevent its recruitment. In all cases of treatment, monitoring recruitment from the seedbank is recommended for up to one year after treating a site. This thesis suggests that localised eradication of N. trichotoma is achievable in as little as three years if (i) above-ground plants are treated, (ii) seedling recruitment from the seedbank is managed intensely within the first year, (iii) high densities of native grass is established to provide competition, and (iv) the addition of new seed is prevented.
- Description: Doctor of Philosophy
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