Amaranthus retroflexus L (redroot pigweed) : effects of elevated CO2 and soil moisture on growth and biomass and the effect of radiant heat on seed germination
- Authors: Weller, Sandra , Florentine, Singarayer , Welgama, Amali , Chadha, Aakansha , Turville, Christopher
- Date: 2021
- Type: Text , Journal article
- Relation: Agronomy Vol. 11, no. 4 (2021), p.
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- Description: Amaranthus retroflexus L. (Amaranthaceae), Redroot pigweed, is native to North America, but has become a weed of agriculture worldwide. Previous research into competition with food crops found it significantly reduces yields. Additionally, taxonomy, biomass allocation, physiological responses to light intensity, water stress, elevated CO2, and herbicide resistance have been inves-tigated. To extend other research findings, we investigated growth and biomass yield in response to (i) soil moisture stress, and (ii) drought and elevated CO2. Additionally, we investigated seed germination rates following exposure to three elevated temperatures for two different time periods. Overall, moisture stress reduced plant height, stem diameter, and number of leaves. Elevated CO2 (700 ppm) appeared to reduce negative impacts of drought on biomass productivity. Heating seeds at 120◦C and above for either 180 or 300 s significantly reduced germination rate. These results inform an understanding of potential responses of A. retroflexus to future climate change and will be used to predict future occurrence of this weed. The finding that exposing seeds to high temperatures retards germination suggests fire could be used to prevent seed germination from soil seed banks, particularly in no-till situations, and therefore may be used to address infestations or prevent further spread of this weed. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. **Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliates “Sandra Weller, Singarayer Florentine, Amali Welgama, Aakansha Chadha, Chrisopher Turville" are provided in this record**
Evaluation of the growth response of arid zone invasive species salvia verbenaca cultivars to atmospheric carbon dioxide and soil moisture
- Authors: Weller, Sandra , Javaid, Muhammad , Florentine, Singarayer
- Date: 2020
- Type: Text , Journal article
- Relation: Rangeland Journal Vol. 42, no. 1 (2020), p. 45-53
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- Description: Although climate change is expected to affect the ecology of many weed species, the nature and scale of these responses is presently not well defined. This presages a suite of potential problems for the agricultural industries. Consequently, we investigated the effects of anticipated climate change on biomass and seed production, for two varieties of wild sage, Salvia verbenaca L. var. verbenaca and Salvia verbenaca var. vernalis Bioss. For the investigation, ambient (400 ppm) and elevated (700 ppm) carbon dioxide conditions, in combination with well-watered (100% field capacity) and drought conditions (60% field capacity), were selected to represent alternative climate scenarios. The alteration in biomass production was represented by a combined measurement of nine variables plant height, stem diameter, number of leaves, number of branches, leaf area, leaf thickness, shoot biomass, root biomass and dry leaf weight, and fecundity was measured via two variables 100 seed weight and number of seeds per plant. All biomass measurements were reduced in a drought situation compared with well-watered conditions in ambient carbon dioxide (400 ppm), and each corresponding measurement was greater under elevated carbon dioxide (700 ppm) regardless of water treatment. In contrast, this was not observed for 100 seed weight or number of seeds per plant. Although a similar profile of a reduction in fecundity parameters was observed under drought conditions compared with well-watered conditions in ambient carbon dioxide, there was an increase in seed mass only for var. verbenaca under elevated carbon dioxide in both water treatments. In addition, there was a very small increase in the number of seeds in this species under drought conditions in elevated carbon dioxide, with neither increase in seed mass or seed number being observed in var. vernalis. These results suggest that although future climate change may result in increased competition of both these varieties with desirable plants, their management strategies will need to focus on effects of increased size of the weeds, rather than only attempting to reduce the seed bank holdings. © 2020 Australian Rangeland Society.
Seed germination response of a potential rangeland weed Psilocaulon granulicaule to selected environmental conditions
- Authors: Ranaweera, Rekha , Weller, Sandra , Florentine, Singarayer
- Date: 2020
- Type: Text , Journal article
- Relation: Australian Journal of Botany Vol. 68, no. 5 (2020), p. 363-368
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- Description: Studies show that just over 620 non-native naturalised plant species have been recorded within the Australian rangelands, some of which have a capacity to cause significant impacts on rangeland flora and grazing activity. Although Psilocaulon granulicaule (Haw.), Schwantes is listed as a highly invasive environmental weed species, there has been no previous research into its seed ecology. Therefore, this study was conducted to investigate the effects of temperature, light, pH, water stress, heat-shock, and salinity on the germination of P. granulicaule. In this study, four temperature regimes covering four different day and night temperature variations (17-7°C, 25-15°C, 30-25°C and 40-30°C) and two light regimes (12-h light-12-h dark, 24-h dark) were investigated. The effects of pH, water stress, heat-shock and salinity were investigated, using pH buffers, polyethylene glycol solutions, three heat shock events under four temperatures and a range of NaCl solutions. These tests were conducted under the identified optimum temperature range (25/15°C) and light regime for seed germination. The results showed that both temperature and photoperiod significantly influenced the germination rate, with 94.2% germination in the 25-15°C range under a 12-h light-12-h dark regime. Higher temperatures (30-40°C) reduced seed germination to <58% germination in both light regimes (57.5%, 12-h light-12-h dark; 54.17%, 24-h dark). The highest germination rates were observed in low pH solutions, high moisture levels, low heat-shocks and low salinity. The study showed that this species is sensitive to environmental factors such as temperature, light, pH, moisture, heat shock and salinity, suggesting that these factors can be used as critical indicators to guide effective management practices to address this weed problem. Given that seeds are sensitive to radiant heat, burning could be used as a tool to effectively manage this species. © 2020 CSIRO.
Influence of selected environmental factors on seed germination and seedling emergence of Dinebra panicea var. brachiata (Steud.)
- Authors: Weller, Sandra , Florentine, Singarayer , Chauhan, Bhagirath
- Date: 2019
- Type: Text , Journal article
- Relation: Crop Protection Vol. 117, no. (2019), p. 121-127
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- Description: Dinebra panicea var. brachiata (Steud.) is related to genus Leptochloa., some species of which are significant rice crop weeds. However, little is known about how D. panicea responds to various environmental cues. This study investigates the effects of temperature, light, salt stress, moisture stress, pH, heat shock, smoke, and burial depth on seeds collected in successive years (2015 and 2016) from Queensland, Australia. Seed germination was higher overall for older seeds (2015) compared to younger (2016) at 30/20 °C and 25/15 °C, but there was less difference between light treatments (12 L/D, 24D) in both temperature ranges for older seeds compared to younger. Increasing moisture and salt stress gradually reduced germination, germination was high over the pH range from pH 4 to pH 10, short term (three minutes) heat exposure to 80 °C or less did not inhibit germination, but there was no significant difference between years for any of these environmental cues. Germination was greatly reduced at 100 °C and eliminated at 120 °C. Smoke significantly inhibited germination. Seeds from both years germinated on the soil surface and emerged from 0.2 cm, with no emergence from deeper than 0.5 cm. The data collected from this study may assist land managers to manage infestations of this weed.
Response of Chloris truncata to moisture stress, elevated carbon dioxide and herbicide application
- Authors: Weller, Sandra , Florentine, Singarayer , Mutti, Navneet , Jha, Prashant , Chauhan, Bhagirath
- Date: 2019
- Type: Text , Journal article
- Relation: Scientific Reports Vol. 9, no. 1 (2019), p. 1-10
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- Description: Herbicide resistance has been observed in Chloris truncata, an Australian native C4 grass and a summer-fallow weed, which is common in no-till agriculture situations where herbicides are involved in crop management. To investigate the role of drought and increased atmospheric carbon dioxide (CO2) in determining weed growth, three trials were conducted using a ‘glyphosate-resistant’ and a ‘glyphosate-susceptible’ biotype. The first two trials tested the effect of herbicide (glyphosate) application on plant survival and growth under moisture stress and elevated CO2 respectively. A third trial investigated the effect on plant growth and reproduction under conditions of moisture stress and elevated CO2 in the absence of herbicide. In the first trial, water was withheld from half of the plants prior to application of glyphosate to all plants, and in the second trial plants were grown in either ambient (450 ppm) or elevated CO2 levels (750 ppm) prior to, and following, herbicide application. In both biotypes, herbicide effectiveness was reduced when plants were subjected to moisture stress or if grown in elevated CO2. Plant productivity, as measured by dry biomass per plant, was reduced with moisture stress, but increased with elevated CO2. In the third trial, growth rate, biomass and seed production were higher in the susceptible biotype compared to the resistant biotype. This suggests that a superior ability to resist herbicides may come at a cost to overall plant fitness. The results indicate that control of this weed may become difficult in the future as climatic conditions change. Supplementary information accompanies this paper at https://doi.org/10.1038/s41598-019-47237-x.
Effect of environmental factors on the germination and emergence of Salvia verbenaca L. cultivars (verbenaca and vernalis) : An invasive species in semi-arid and arid rangeland regions
- Authors: Javaid, Muhammad , Florentine, Singarayer , Ali, Hafiz , Weller, Sandra
- Date: 2018
- Type: Text , Journal article
- Relation: PLoS ONE Vol. 13, no. 3 (2018), p. 1-20
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- Description: Salvia verbenaca (wild sage) is a commonly cultivated herbal medicine plant, which is native to the Mediterranean climate regions of Europe, Africa, Asia and the Middle East. However, it has become an invasive species in semi-arid and arid regions of southern Australia. Two varieties are present in this region, var. verbenaca and var. vernalis, each of which can be distinguished by differences in morphology and flowering period. Following trials to determine the optimum temperate regime for germination and response to light and dark, seeds of both varieties were tested for their response to variations in pH, moisture stress, salinity, and burial depth. The temperature and light trial was carried out using three different temperature regimes; 30/20C, 25/15C and 20/12C, and two light regimes; 12 hours light/12 hours dark and 24 hours dark, with var. vernalis responding to relatively higher temperatures than var. verbenaca. The germination rate of neither species was significantly inhibited by complete darkness when compared to rates under periodic light exposure. Both varieties germinated at near optimum rates strongly to very strongly in all pH buffer solutions, from pH 5 to pH 10, but they responded most strongly at neutral pH. Var. vernalis showed slightly more tolerance to reduced moisture availability, moderate to strong salinity, and burial depth, compared to var. verbenaca. However, even a fairly shallow burial depth of 2 cm completely inhibited germination of both varieties. Thus, in circumstances where both varieties are present in a soil seedbank, var. vernalis could be expected to establish in more challenging conditions, where moisture is limited and salinity is ‘moderate to high’, implying that it is a more serious threat for invasive weed in conditions where crop plants are already challenged.
Seed germination response of a noxious agricultural weed Echium plantagineum to temperature, light, pH, drought stress, salinity, heat and smoke
- Authors: Florentine, Singarayer , Weller, Sandra , King, Alannah , Florentine, Arunthathy , Dowling, Kim , Westbrooke, Martin , Chauhan, Bhagirath
- Date: 2018
- Type: Text , Journal article
- Relation: Crop and Pasture Science Vol. 69, no. 3 (2018), p. 326-333
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- Description: Echium plantagineum is a significant pasture weed in the Mediterranean climatic zone of several countries, including Australia. This invasive weed, introduced as an ornamental into Australia (where it is known as Paterson's curse), quickly became established and is now a significant weed of agriculture. Although E. plantagineum is a well-established, highly competitive weed that thrives under disturbance and is tolerant of a wide variety of conditions, including varying soil moisture and drought, and some aspects of its ecology remain unknown. This study investigated germination response to temperature and light, pH, soil moisture, salinity, and pre-germination exposure of seed to heat and smoke. Temperature was found to be more influential on germination than light and the species is tolerant to a wide range of pH. However, available moisture may limit germination, as may elevated salinity. Management of this weed requires approaches that minimise soil seedbank input or prevent germination of soil seedbanks.
An investigation of the effects of stage of ensilage on Nassella neesiana seeds, for reducing seed viability and injury to livestock
- Authors: Weller, Sandra , Florentine, Singarayer , Sillitoe, Jim , Grech, Charles , McLaren, David
- Date: 2016
- Type: Text , Journal article
- Relation: Scientific Reports Vol. 6, no. (2016), p. 1-7
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- Description: The noxious weed Nassella neesiana is established on a wide range of productive land throughout southeastern Australia. N. neesiana seeds, when mature, are sharp, causing injury to livestock, thus posing a problem in fodder bales. To reduce infestations of agricultural weeds in situ, production of silage from weed-infested pastures is practised as part of integrated weed management (IWM). However, there is little data to demonstrate whether this process is useful to reduce infestations or the harmful properties of N. neesiana. Therefore, the minimum duration of ensilage required to reduce the viability of N. neesiana seeds was investigated, both with and without addition of ensilage inoculants in this process. Also, the decreasing propensity of the seeds to injure livestock, after various times and conditions of ensilage, was assessed. Ensilage inoculant reduced seed germination probability to zero after 35 days. When no inoculant was added, zero viability was achieved after 42 days. A qualitative assessment of the hardness of ensilaged seeds found seed husks were softer (and therefore safer) after 42 days, whether inoculant was used or not. Therefore, we suggest that both the viability of N. neesiana seeds and hardness of seed casings are significantly reduced after 42 days, thereby reducing the risks of seed dispersal and injury to livestock.
Influence of selected environmental factors on seed germination and seedling survival of the arid zone invasive species tobacco bush (Nicotiana glauca R. Graham)
- Authors: Florentine, Singarayer , Weller, Sandra , Graz, Patrick , Westbrooke, Martin , Florentine, Arunthathy , Javaid, Muhammad , Fernando, Nimesha , Chauhan, Bhagirath , Dowling, Kim
- Date: 2016
- Type: Text , Journal article
- Relation: Rangeland Journal Vol. 38, no. 4 (2016), p. 417-425
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- Description: 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 12h of light and 12h 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 1.5cm. 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. © 2016 Australian Rangeland Society.
Detecting the seeds of Nassella neesiana in large round hay bales, by means of non-destructive core sampling
- Authors: Weller, Sandra , Florentine, Singarayer , Sillitoe, Jim , Grech, Charles , McLaren, David , Chauhan, Bhagirath
- Date: 2015
- Type: Text , Journal article
- Relation: Plos One Vol. 10, no. 9 (2015), p.
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- Description: In the last three decades or so there has been a significant increase in fodder trading, both in terms of the quantity of fodder traded and in terms of its economic value to the industry. Often, this fodder type may be supplied free of charge to graziers in distress due to circumstances that follow natural disasters such as bushfires, drought, and flood. However, because of the obvious urgency arising from these situations, it is suspected that much relief fodder may unintentionally pose an elevated risk for dispersal of weeds since it may be supplied from pasture not normally used for trade in fodder, and therefore is of unknown quality. Previous destructive method to detect weed propagules in bales of fodder are cumbersome, time consuming and of limited ecological and statistical value. Therefore, objective of this paper was to development of a convenient method to assess round pasture hay bales for the presence of weed propagules, to prevent unintentional spread of noxious species in hay bales. To examine this objective known quantity of seeds were added in a series of distributions to bales of seed free pasture hay, and a positive correlation for the amount of seed added per bale with that recovered in core samples was observed. Whilst the number of seeds detected per bale varied according to the distribution of seeds within the bales and the number of cores analysed, the absolute detection of seeds suggests that this sampling method is worthy of further examination. In addition, a pragmatic estimation of bale remnants after stock feeding has been investigated to more closely estimate the potential size of the remaining seed bank. The authors propose that development of this approach is timely, in the light of future climatic uncertainty driving extreme weather events that increase the need for relief fodder, which can be a potential vector for the spread of noxious weed seeds.
The need for speed: Timely prevention of the dispersal of noxious weeds in relief fodder using efficient sampling procedures
- Authors: Weller, Sandra , Florentine, Singarayer , Sillitoe, Jim , Grech, Charles , McLaren, David , Chauhan, Bhagirath
- Date: 2015
- Type: Text , Journal article
- Relation: Crop Protection Vol. 70, no. (2015), p. 21-27
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- Description: Invasive and noxious weeds are well known as a pervasive problem, imposing significant economic burdens on all areas of agriculture. Whilst there are multiple possible pathways of weed dispersal in this industry, of particular interest to this discussion is the unintended dispersal of weed seeds within fodder. During periods of drought or following natural disasters such as wild fire or flood, there arises the urgent need for 'relief' fodder to ensure survival and recovery of livestock. In emergency situations, relief fodder may be sourced from widely dispersed geographic regions, and some of these regions may be invaded by an extensive variety of weeds that are both exotic and detrimental to the intended destination for the fodder. Pasture hay is a common source of relief fodder and it typically consists of a mixture of grassy and broadleaf species that may include noxious weeds. When required urgently, pasture hay for relief fodder can be cut, baled, and transported over long distances in a short period of time, with little opportunity for prebaling inspection. It appears that, at the present time, there has been little effort towards rapid testing of bales, post-baling, for the presence of noxious weeds, as a measure to prevent dispersal of seeds. Published studies have relied on the analysis of relatively small numbers of bales, tested to destruction, in order to reveal seed species for identification and enumeration. The development of faster, more reliable, and non-destructive sampling methods is essential to increase the fodder industry's capacity to prevent the dispersal of noxious weeds to previously unaffected locales.
Finding needles in a haystack: an investigation of non-destructive method to detect the seeds of Chilean needle grass (Nassella Neesiana (Trin. & Rupr.) Barkworth) in round hay bales
- Authors: Weller, Sandra , Florentine, Singarayer , Ambrose, Graeme , Grech, Charles , McLaren, David
- Date: 2012
- Type: Text , Conference paper
- Relation: 18th Australasian Weeds Conference p. 222-240
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- Description: Preserved fodder is a key component in modern agricultural practice. Hay bales are commonly provisioned for livestock. Unfortunately this is also a significant source of new weed infestations, including those of noxious species. Because hay bales may be of a low absolute value the usual approaches for weed control, for example herbicide treatment, may be expensive to apply and therefore not justified by the expected economic returns for this commodity. The methods of detecting weed seeds in bales that have been employed to date suffer from several deficiencies. These include the inefficiently long time needed for testing, loss of the commodity by overly destructive sampling methods and a serious potential for a lack of ecological representation for the presence of weeds. It is proposed that an alternative method, which is both potentially more rapid and more ecologically representative for detecting the presence of the seeds of noxious weeds in hay bales should be devised.
Detection, quantification and management of the dispersal of Nassella neesiana (Chilean Needle Grass) seeds in hay bales
- Authors: Weller, Sandra , Florentine, Singarayer , Ambrose, Graeme , Grech, Charles , McLaren, David
- Date: 2010
- Type: Text , Conference paper
- Relation: Paper presented at 17th Australasian Weeds Conference: New Frontiers in New Zealand, Together we can beat the weeds p. 428-430
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- Description: Summary This paper outlines a project that intends to investigate the link between the occurrences of weeds in pasture hay crops and weed seeds in bales. Noxious weed in particular pose a threat to the livelihoods of primary producers in this manner. As an example of a noxious weed, this project will investigate Nassella neesiana, Chilean needle grass. This species is a restricted (noxious) weed that infests roadsides, native grasslands and pastures that may be baled for hay. In Victoria it has the potential to cause significant economic harm to agricultural areas and the trade in fodder and hay. This project aims to develop methods for the detection of weed seeds in hay bales and provide more information about the role of hay machinery in their spread. Later, we will investigate the extent of seed shedding from hay bales during transportation by road. This project will attempt to correlate the percentage cover of N. neesiana prior to harvest with the seed content of bales. Trial core samples from bales indicate that seeds of N. neesiana and other grass species were present. However, a correlation has not yet been established between weed biomass and the seed content of bales.