Plant population dynamics in subterranean clover and murex medic swards. I. Size and composition of the seed bank

Blumenthal, MJ; Ison, RL

doi:10.1071/ar9940913

Cited by 6 publications

(5 citation statements)

References 20 publications

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“…The observed changes in seedling survival and seed dormancy breakdown rates altered the predicted performance of transgenic and non‐transgenic lines in grasslands with different floristic composition, which is not surprising as variation in seed dormancy mechanisms including hardseededness and embryo dormancy are known to critically influence the population dynamics of subterranean clover (Blumenthal & Ison 1994; Evans & Hall 1995; Piano et al. 1996).…”

Section: Discussionmentioning

confidence: 90%

“…The observed changes in seedling survival and seed dormancy breakdown rates altered the predicted performance of transgenic and non-transgenic lines in grasslands with different floristic composition, which is not surprising as variation in seed dormancy mechanisms including hardseededness and embryo dormancy are known to critically influence the population dynamics of subterranean clover (Blumenthal & Ison 1994;Evans & Hall 1995;Piano et al 1996). While overall survival, growth and fecundity of both lines were higher in grassland plots dominated by exotic annual species, a distinct genotype by environment interaction was evident in seedling survival and predicted population growth rates across the community gradient.…”

Section: Discussionmentioning

confidence: 91%

“…Variation in seed dormancy mechanisms including hardseededness (the presence of an impermeable seed coat) and embryo dormancy are known to critically influence the population dynamics of subterranean clover (Blumenthal & Ison 1994;Evans & Hall 1995;Piano et al 1996). To determine the initial level of dormancy of second-generation seed produced by transgenic and non-transgenic plants, 150 seeds from each line were sampled from randomly selected burrs on 24 January 2002, placed on moist filter paper, and stored at 15°C for 14 days.…”

Section: Second-generation Seed Germination and Burial Experimentsmentioning

confidence: 99%

Section: Second‐generation Seed Germination and Burial Experimentsmentioning

confidence: 99%

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Ecological risk assessment of transgenic pasture plants: a community gradient modelling approach

et al. 2004

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The extension of transgene technology to pasture species presents new challenges for ecological risk assessment because, unlike most crops, pasture plants are well adapted for persistence in mixed plant communities and are an important source of invasive species worldwide. Despite this, the impact of transgenic pasture plants on native ecosystems remains relatively unstudied. Here we use a community gradient modelling approach to investigate the performance of subterranean clover containing a nutrition-enhancing transgene over a range of ecologically important grassland communities at a study site in south-eastern Australia. Our data, which were collected over a full annual growing season, show that the transgenic clover line has different seedling survival and seed dormancy breakdown rates than the commercial non-transgenic line, which suggests that transgenic populations will decline faster than non-transgenic ones in perennial native grassland communities but could, under optimal climatic conditions, have potentially higher growth rates in grazed annual grasslands. These results demonstrate that changes to ecologically important demographic parameters can occur in plants containing transgenes that are not typically considered fitness enhancing, and that genotype by environment interactions and management regimes that impact on these parameters may influence the invasiveness of transgenic plants. Our study also demonstrates the utility of incorporating plant community gradient modelling into ecological risk assessment protocols designed for transgenic pasture plants.

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Section: Discussionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 91%

Section: Second-generation Seed Germination and Burial Experimentsmentioning

confidence: 99%

Section: Second‐generation Seed Germination and Burial Experimentsmentioning

confidence: 99%

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Ecological risk assessment of transgenic pasture plants: a community gradient modelling approach

et al. 2004

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“…Many studies have been conducted in Mediterranean environments in annual species such as Trifolium subterraneum L. and Medicago spp. (Blumenthal and Ison, 1994;Piano et al, 1996;Taylor, 1996a;1996b;2005;Norman et al, 2006) to characterize their patterns of seed softening (the process whereby the seed coat becomes permeable).…”

Section: Introductionmentioning

confidence: 99%

Seed softening patterns of forage legumes in a temperate/subtropical environment in Uruguay

Canto

Reyno

Real

et al. 2013

Chilean J. Agric. Res.

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Few studies have been conducted in annual and perennial forage legumes to investigate the development of hardseededness and the subsequent pattern of seed softening in temperate and subtropical regions of South America. Experiments were conducted during 2007 and 2008 in central Uruguay to follow the pattern of seed softening in 35 annual and perennial forage legumes, including three native species of Uruguay and five commercial cultivars. Newly ripened seeds of each plant material were placed in mesh packets on the soil surface in mid-summer. Samples were recovered monthly for germination tests and the proportion of residual hard seeds determined. The native species Adesmia bicolor (Poir.) DC., Adesmia securigerifolia Herter, and Ornithopus micranthus (Benth.) Arechav., together with Ornithopus pinnatus (Mill.) Druce cv. INIA Molles behaved similarly. They showed high levels of initial hard seed from 78% in A. bicolor to 99% in A. securigerifolia and O. pinnatus cv. INIA Molles in 2007; displayed pulses of seed softening, particularly in autumn, and retained moderate levels of residual hard seed for the development of a soil seed bank ranging from 15% in A. bicolor to 49% in O. micranthus. These appear to be desirable characteristics for persistence of forage legumes in subtropical grasslands, both for annual and perennial species. Trifolium repens L. and Lotus corniculatus L. produced few hard seeds, only 2% and 13% respectively were hard after 1-mo in the field and were completely soft by July placing extra reliance on their vegetative propagation for persistence. Materials of L. arenarius Brot. showed pronounced late autumn softening, while materials of L. ornithopodioides L. showed extremely high levels of hardseededness (between 96% and 100%) and no softening during the evaluation period, apart from two materials that were completely soft seeded. Mediterranean forage legumes should be properly evaluated in temperate and subtropical regions as their seed softening behavior is likely to be substantially modified in these summer moist environments.

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Effect of phalaris (Phalaris aquatica L.) and lucerne (Medicago sativa L.) density on seed yield and regeneration of subterranean clover (Trifolium subterraneum L.)

Dear¹,

Cocks²,

Swan³

et al. 2000

Aust. J. Agric. Res.

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A mixture of 3 subterranean clover (Trifolium subterraneum L.) cultivars (cvv. Goulburn, Seaton Park, and Dalkeith) was grown with 5–40 plants/m2 of phalaris (Phalaris aquatica L.) or lucerne (Medicago sativa L.) for 3 years at Wagga Wagga, NSW (147°21´E, 35°03´S). Clover seed yield was assessed each year, the number of regenerating clover seedlings was counted, herbage yield of clover and the perennials was measured, and the change in perennial density recorded. The influence of perennials on water availability in spring and light during clover seed set was also examined. The impact of perennial density on clover was assessed using regression analyses. In each of the 3 years, subterranean clover seed yield was negatively related to perennial density, but phalaris suppressed clover seed yield more than equivalent densities of lucerne in 2 of the years. Clover seed yield was positively related (R2 = 0.30–0.85) to clover biomass in spring in all 3 years (except for subterranean clover in phalaris in 1994) and to the proportion of total photosynthetically active radiation reaching the clover canopy beneath the perennial (R2 = 0.33–0.83) in 2 of the 3 years. There was a positive relationship between clover seedling regeneration in autumn and size of the summer seed bank in both years in lucerne (R2 = 0.40–0.76) and in 1 year in phalaris (R2 = 0.76) and a negative association between perennial density and clover seedling regeneration. The rate at which the surface profile (0–37 cm) dried in spring was independent of phalaris and lucerne density over the 3 years and did not differ from that of pure clover. The late season clover cultivar, Goulburn, constituted between 57% and 79% of the seed bank following seed set, substantially more than the earlier flowering cultivars, Seaton Park and Dalkeith. Neither perennial density nor species changed the relative competitiveness of the 3 cultivars. The high seed yield of Goulburn and the lack of a perennial-induced change in surface soil water in spring suggest that growing perennials in association with subterranean clover does not increase the level of moisture stress during clover seed set. The good performance of Goulburn is attributed to superior competitive ability for light in late spring. The basal area occupied by lucerne and phalaris increased with perennial density in each of the first 2 years. However, in the third year, phalaris basal area was similar at all densities. The findings suggest that sowing low densities of lucerne should assist in promoting seed yield and regeneration of subterranean clover. Management of phalaris, which has the capacity to substantially increase plant size at low densities, may require additional strategies such as more frequent grazing in spring.

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Plant population dynamics in subterranean clover and murex medic swards. I. Size and composition of the seed bank

Cited by 6 publications

References 20 publications

Ecological risk assessment of transgenic pasture plants: a community gradient modelling approach

Ecological risk assessment of transgenic pasture plants: a community gradient modelling approach

Seed softening patterns of forage legumes in a temperate/subtropical environment in Uruguay

Effect of phalaris (Phalaris aquatica L.) and lucerne (Medicago sativa L.) density on seed yield and regeneration of subterranean clover (Trifolium subterraneum L.)

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