The Experts below are selected from a list of 246 Experts worldwide ranked by ideXlab platform
Tom J De Jong - One of the best experts on this subject based on the ideXlab platform.
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Testing sex‐allocation theory: flowers vs seeds in hermaphrodite plants
Oikos, 2000Co-Authors: Mariëlle C. J. Rademaker, Tom J De JongAbstract:Plants of the self-compatible Echium uulgare and Cynoglossum Officinale frequently abort seeds, while all flowers contain pollen. Sex allocation then changes with the seed to flower ratio. Based on our field data, we can draw fitness sets. The analysis shows that the fitness set is bowed out and that hermaphroditism is evolutionarily stable in both species. It also predicts correctly the size-dependent pattern of seeds per flower observed in C. Officinale in the field, where small plants produce 0.39 and large plants 0.85 seeds per flower. The model fails to predict the pattern in E. vulgare.
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Is the threshold size for flowering in Cynoglossum Officinale fixed or dependent on environment
New Phytologist, 1998Co-Authors: Tom J De Jong, Leentje Goosen-de Roo, P. G. L. KlinkhamerAbstract:In the monocarpic perennial Cynoglossum Officinale L. the probability of flowering is related to the size of the plant. In previous work it was observed that this relation varies between years. We hypothesized that variable conditions during the winter, the period of vernalization, explain this variation. We collected plants from the field in autumn and placed these under different simulated winter conditions in a climate room. In contrast to our hypothesis, the probability of initiating flowering at a given size was not affected by: (a) the temperature during the cold period, (b) the duration of the cold period, or (c) the application of a plant hormone (GA3) or an inhibitor of gibberellin synthesis (paclobutazol) during the cold period. Winter cold is not necessary for floral initiation, and is only required for elongation of the inflorescence. It is unlikely that winter temperature affects the fraction of plants flowering. Subsequent morphological investigation of flower development in material collected in the field showed that large plants had primordial inflorescences well before vernalization, sometimes as early as August. In plants grown from seeds under constant conditions in a climate room, the probability of initiating the inflorescence differed for plants grown at various temperatures (34·1% at 15°C, 100% at 20°C, and 95% at 25°C). Our results suggest that environmental conditions in August and September, up to 10 months before actual flowering, could affect the fraction of flowering plants.
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Bidirectional selection on threshold size for flowering in Cynoglossum Officinale (hound's-tongue)
Heredity, 1995Co-Authors: Renate A. Wesselingh, Tom J De JongAbstract:Previous studies have demonstrated that many facultative biennials show variation in threshold size for flowering. In order to quantify the genetic variation for this character, we performed a two-way artificial selection experiment on threshold size in Cynoglossum Officinale. The parental generation, established from seed from a natural population, showed large variation in threshold sizes (2.6- 13.4 g). After one generation of selection for low threshold sizes all plants in the F1 flowered at sizes below 3.2 g. In the high selection line none of the F1 plants under 3.6 g flowered, and there were very large nonflowering plants (up to 17.2 g). By interpreting the logistic regression of flowering probability on plant size as a cumulative frequency distribution of threshold sizes, we could derive the frequency distributions of threshold sizes in each generation. These were used to estimate the narrow-sense heritabilities by the standard procedure for artificial selection on a quantitative character. This gave 'heritabilities' of 0.35 and 0.32 for the high and low selection lines, respectively. A previously constructed optimization model, applied to the population in our study area, predicted strong selection against low threshold sizes, but a fairly equal fitness for threshold sizes around and above the optimum. This flat fitness profile may explain why the natural population of Cynoglossum Officinale harbours extensive genetic variation for this character.
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Geographical variation in threshold size for flowering in Cynoglossum Officinale
Acta Botanica Neerlandica, 1993Co-Authors: Renate A. Wesselingh, Tom J De Jong, Peter G. L. Klinkhamer, Marinke J. Van Dijk, Els G. M. SchlatmannAbstract:We investigated variation in two traits that determine generation time, cold- and size-requirement for flowering, within and among EuroPean populations for the monocarpic perennial Cynoglossum Officinale. When grown in an experimental garden in Leiden, no annual individuals were found among plants originating from 22 locations; all plants were biennial under nutrient-rich growing conditions. In a controlled-environment experiment, in which plants received an artificial cold treatment, flowering probability increased gradually with plant size for plants from two natural populations, signifying a large within-population variation in threshold size for flowering. The relationships between plant size and flowering of these two groups were significantly different: plants from Holkham (England) had much higher threshold sizes than plants from Meijendel (The Netherlands). Three plant groups originating from botanic gardens showed a sharp increase in flowering probability with size, indicating less variation in threshold size. Significant differences existed among all five groups. Results indicate the possibility that natural selection acts upon threshold size for flowering in Cynoglossum Officinale
Brian E. Ellis - One of the best experts on this subject based on the ideXlab platform.
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inhibition of seed germination and seedling growth by hound s tongue Cynoglossum Officinale l seed leachate
Weed Biology and Management, 2005Co-Authors: Abdur Rashid, Brian E. Ellis, Nancy H. Furness, Mahesh K. UpadhyayaAbstract:The leaching of phenolics from decoated seeds, seed coats and pericarps of hound’s-tongue (Cynoglossum Officinale L.), factors affecting leaching, and seed germination and seedling growth inhibitory activities of the leachate were investigated. Embryonic axes and cotyledons contained a large amount of methanol-soluble phenolic substances. Decoated seeds released phenolics into an aqueous incubation medium and this solution was capable of inhibiting root elongation of several grassy and broadleaf species, but not of hound’s-tongue. The leachate and the phenolic fraction of the leachate inhibited germination of bluebunch wheatgrass (Pseudoroegnaria spicata (Pursh) A. Love [syn. Agropyron spicatum (Pursh) Scribn. and J. G. Sm.]). The non-phenolic fraction of the leachate did not inhibit seed germination or root and shoot elongation of bluebunch wheatgrass. Low oxygen and an increasing temperature significantly increased the amount of phenolic substances leached from decoated seeds. Increased leaching of phenolic substances related to an increasing temperature was associated with the loss of seed viability. Further investigation of the role of water-extractable hound’s-tongue seed phenolics in the interaction of this species with its biotic environment under field conditions is needed to determine the ecological significance of these findings.
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Inhibition of seed germination and seedling growth by hound’s‐tongue (Cynoglossum Officinale L.) seed leachate
Weed Biology and Management, 2005Co-Authors: Abdur Rashid, Brian E. Ellis, Nancy H. Furness, Mahesh K. UpadhyayaAbstract:The leaching of phenolics from decoated seeds, seed coats and pericarps of hound’s-tongue (Cynoglossum Officinale L.), factors affecting leaching, and seed germination and seedling growth inhibitory activities of the leachate were investigated. Embryonic axes and cotyledons contained a large amount of methanol-soluble phenolic substances. Decoated seeds released phenolics into an aqueous incubation medium and this solution was capable of inhibiting root elongation of several grassy and broadleaf species, but not of hound’s-tongue. The leachate and the phenolic fraction of the leachate inhibited germination of bluebunch wheatgrass (Pseudoroegnaria spicata (Pursh) A. Love [syn. Agropyron spicatum (Pursh) Scribn. and J. G. Sm.]). The non-phenolic fraction of the leachate did not inhibit seed germination or root and shoot elongation of bluebunch wheatgrass. Low oxygen and an increasing temperature significantly increased the amount of phenolic substances leached from decoated seeds. Increased leaching of phenolic substances related to an increasing temperature was associated with the loss of seed viability. Further investigation of the role of water-extractable hound’s-tongue seed phenolics in the interaction of this species with its biotic environment under field conditions is needed to determine the ecological significance of these findings.
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ROLE OF SEED COAT IN REGULATION OF SEED DORMANCY IN HOUNDSTONGUE (Cynoglossum Officinale)
Weed Science, 1998Co-Authors: Elisa Stabell, Mahesh K. Upadhyaya, Brian E. EllisAbstract:Brian E. Ellis University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 To understand the role of the seed coat in regulation of houndstongue seed dormancy, the effects of manipulation of seed coat integrity on seed germination and 02 uptake were studied. The results suggest that the seed coat of this weed regulates dormancy in part by interfering with the diffusion of 02 to the embryo. Scanning electron microscopy showed a network of ridges on the seed coat surface that were partially dissolved following 1.5 min of sulphuric acid scarification. Mechanical scarification removed fragments of the seed coat surface. Both scarification treatments stimulated seed germination. Supply of an elevated level of 02 also stimulated seed germination. 02 uptake by seeds imbibed in O2-saturated water was 150% higher than that for seeds imbibed in air-saturated water. Although all treatments that stimulated seed germination also stimulated 02 uptake, there was a lack of a consistent, quantitative relationship between increases in 02 uptake and seed germination in various experiments. This suggests that limitation of 02 availability to the embryo is not the only factor involved in regulation of houndstongue seed dormancy by the seed coat. Mechanical restriction of embryo expansion by the seed coat may also be important. Methanol-insoluble phenolics constituted < 1% of the total phenolic pool in the embryo. Their potential oxidation could not account for more than a small fraction of the previously reported massive stimulation of 02 uptake by the embryo upon decoating. The present 02 uptake and seed germination studies indicate that not all of the large increase in 02 uptake following decoating is essential for houndstongue seed germination.
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development of seed coat imposed dormancy during seed maturation in Cynoglossum Officinale
Physiologia Plantarum, 1996Co-Authors: E. Stabell, Mahesh K. Upadhyaya, Brian E. EllisAbstract:The relationship between seed phenolics and appearance of seed coat-imposed dormancy during seed development in Cynoglossum Officinale L. was studied. Up to 24 days after anthesis, seeds failed to germinate upon imbibition in Petri dishes at 25°C. At 44 days after anthesis, seeds were fully germinable ; removal of seed coats did not improve their germination or O 2 uptake. At 72 days after anthesis, mature seeds at the base of the cyme did not germinate unless their coats were removed. Removal of seed coat also stimulated O 2 uptake at this harvest date. The methanol-soluble phenolic content of the seeds increased during the early stages of seed development, in both the seed coat and the embryo. As seed development continued, the methanol-soluble phenolic content of the embryo stabilized, but that of the seed coat declined. This decline was associated with an increase in the thioglycolic acid-soluble phenolics, presumably lignins, in the seed coat. These results suggest that polymerization of methanol-soluble phenolics into lignins in the seed coat during later stages of seed development renders the seed coat of C. Officinale impermeable to O 2 , and thus keeps the seed dormant.
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Development of seed coat‐imposed dormancy during seed maturation in Cynoglossum Officinale
Physiologia Plantarum, 1996Co-Authors: E. Stabell, Mahesh K. Upadhyaya, Brian E. EllisAbstract:The relationship between seed phenolics and appearance of seed coat-imposed dormancy during seed development in Cynoglossum Officinale L. was studied. Up to 24 days after anthesis, seeds failed to germinate upon imbibition in Petri dishes at 25°C. At 44 days after anthesis, seeds were fully germinable ; removal of seed coats did not improve their germination or O 2 uptake. At 72 days after anthesis, mature seeds at the base of the cyme did not germinate unless their coats were removed. Removal of seed coat also stimulated O 2 uptake at this harvest date. The methanol-soluble phenolic content of the seeds increased during the early stages of seed development, in both the seed coat and the embryo. As seed development continued, the methanol-soluble phenolic content of the embryo stabilized, but that of the seed coat declined. This decline was associated with an increase in the thioglycolic acid-soluble phenolics, presumably lignins, in the seed coat. These results suggest that polymerization of methanol-soluble phenolics into lignins in the seed coat during later stages of seed development renders the seed coat of C. Officinale impermeable to O 2 , and thus keeps the seed dormant.
P. G. L. Klinkhamer - One of the best experts on this subject based on the ideXlab platform.
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Size-Dependent Sex Allocation in Cynoglossum Officinale for Different Genotypes Under Uniform Favourable Conditions
Plant Biology, 1999Co-Authors: Mariëlle C. J. Rademaker, P. G. L. KlinkhamerAbstract:: Field observations showed that small plants often have lower female investment than large plants. Field-collected data do not elucidate, however, whether this pattern is an in herent effect of size or if it is caused by poorer environmental quality of sites where small plants are growing and/or by geno-typic differences between small and large plants. Therefore, the relationship between plant mass and flower and seed pro duction was measured under favourable conditions using full-sibs and clones of Cynogiossum Officinale. The aim of this study is to determine if the pattern of size-dependent gender was maintained if both small and large plants are grown under fa vourable conditions, and if this pattern is consistent among genotypes. Over all genotypes, smaller plants produced more flowers per unit plant mass compared to large plants. On the other hand, seed production per unit plant mass did not significantly differ between plants of different sizes. As a result, the number of seeds per flower increased with increasing plant mass, large plants produced 1.5 times more seeds per flower compared to small plants. Thus small plants emphasize the male side, whereas large plants emphasize the female side of production. We conclude that, even under favourable environmental condi tions, all genotypes examined maintain size-dependent sex allo cation (SDS). When analysed separately, we found no genetic variation in seed production among genotypes (full sibs and clones). In con trast, genotypes differed significantly in flower production. Nei ther the number of seeds per gram plant mass nor per flower differed significantly among genotypes. In our experiment no evidence was found for a negative genetic correlation between flower production per unit plant mass and seed production per unit plant mass.
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Is the threshold size for flowering in Cynoglossum Officinale fixed or dependent on environment
New Phytologist, 1998Co-Authors: Tom J De Jong, Leentje Goosen-de Roo, P. G. L. KlinkhamerAbstract:In the monocarpic perennial Cynoglossum Officinale L. the probability of flowering is related to the size of the plant. In previous work it was observed that this relation varies between years. We hypothesized that variable conditions during the winter, the period of vernalization, explain this variation. We collected plants from the field in autumn and placed these under different simulated winter conditions in a climate room. In contrast to our hypothesis, the probability of initiating flowering at a given size was not affected by: (a) the temperature during the cold period, (b) the duration of the cold period, or (c) the application of a plant hormone (GA3) or an inhibitor of gibberellin synthesis (paclobutazol) during the cold period. Winter cold is not necessary for floral initiation, and is only required for elongation of the inflorescence. It is unlikely that winter temperature affects the fraction of plants flowering. Subsequent morphological investigation of flower development in material collected in the field showed that large plants had primordial inflorescences well before vernalization, sometimes as early as August. In plants grown from seeds under constant conditions in a climate room, the probability of initiating the inflorescence differed for plants grown at various temperatures (34·1% at 15°C, 100% at 20°C, and 95% at 25°C). Our results suggest that environmental conditions in August and September, up to 10 months before actual flowering, could affect the fraction of flowering plants.
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phenotypic gender in plants effects of plant size and environment on allocation to seeds and flowers in Cynoglossum Officinale
Oikos, 1993Co-Authors: P. G. L. KlinkhamerAbstract:Phenotypic femaleness increases with plant size (dry mass) in the monocarpic perennial Cynoglossum Officinale L.: in the field small plants produce, relative to their weight, many flowers with few seeds per flower, whereas large plants produce relatively few flowers with more seeds per flower. The question is whether size affects gender directly or whether the relationship between size and gender stems from a common factor. In the field large plants may grow on sites with high nutrient availability and therefore have higher nutrient concentrations or large plants may occupy spots with better environmental conditions during the seed filling stage. In an experiment in a coastal dune habitat we found no correlation between leaf nutrient concentration and plant size (...)
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Size-dependent root herbivory on Cynoglossum Officinale
Oikos, 1992Co-Authors: Adriana H Prins, Henk W. Nell, P. G. L. KlinkhamerAbstract:The weevil Ceuthorhynchus (Boraginobius) cruciger was the most important root herbivore of the biennial herb Cynoglossum Officinale in Meijendel, The Netherlands. Only a few other species were found, but always in less than 5% of the plants. The infestation level of flowering plants of C. Officinale was 22% in 1988, 56% in 1989 and 61% in 1990; in rosettes 0% in 1988 and 6% in 1989. Weevil attack was size-dependent: weevils preferred large plants over small plants and, when controlling for size, flowering plants over rosettes
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Meta-population dynamics of biennial plants: how to exploit temporary habitats
Acta Botanica Neerlandica, 1992Co-Authors: E Van Der Meijden, T. J. De Jong, P. G. L. Klinkhamer, C. A. M. Van WijkAbstract:SUMMARY Extinction of local populations of plants of many biennial plant species has been frequently reported. Survival of these species on the meta-population level implies a balance between extinction and regeneration, either through seed dispersal or from the seedbank. We distinguish between three types of biennials (transient, fugitive and persistent) and review the relation between dynamics of local populations and habitat characteristics, such as disturbance. Some species are safe-site limited whereas other species demonstrate a combination of safe-site and seed limitation. Meta-population dynamics are illustrated with two examples (Senecio jacobaea and Cynoglossum Officinale). We distinguish between patch dynamics (loss and genesis of sites that are suitable for population development) and meta-population dynamics of biennials (population behaviour within and between sites, and dispersal). A hypothesis is developed on the regulation of patch dynamics. Finally we discuss the question: what makes biennials suited for exploiting temporary habitats?
Peter G. L. Klinkhamer - One of the best experts on this subject based on the ideXlab platform.
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selective seed abortion increases offspring survival in Cynoglossum Officinale boraginaceae
American Journal of Botany, 2001Co-Authors: Chantal Melser, Peter G. L. KlinkhamerAbstract:Selective embryo abortion is one of the evolutionary explanations for the surplus of ovules found in many plant species. To manipulate the level of embryo abortion, we removed ovules and applied nutrients to plants of Cynoglossum Officinale(Boraginaceae) after they started to flower. From these two treatments and a control series, seeds were collected, germinated, and transplanted in the field to assess the quality of the resulting offspring. Nutrient addition did not increase the number of seeds per flower significantly. Fewer embryos were aborted in the ovule removal treatment. The seeds produced in the ovule removal treatment had a significantly greater mass and significantly lower survival than the offspring from the control group. This difference in survival indicates that offspring of lower quality are selectively aborted in the control group. Offspring from the nutrient addition treatment survived longer. The offspring of the treatments did not differ significantly from the control group in growth. Simple mathematical calculations, based on the differences in offspring quality that we found, indicate that the selective abortion hypothesis can be an important factor explaining the advantage of the ‘‘surplus production’’ of ovules.
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Direct and indirect estimates of the selfing rate in small and large individuals of the bumblebee pollinated Cynoglossum Officinale L (Boraginaceae)
Ecology Letters, 1999Co-Authors: Klaas Vrieling, P. Saumitou- Laprade, J. Cuguen, H. Van Dijk, J. De Jong, Peter G. L. KlinkhamerAbstract:We measured the relationship between selfing rates and flower number in an experimental population of bumblebee pollinated Cynoglossum Officinale, with plants differing in flower number. Results were compared with the prediction of a model based on pollen dynamics and pollinator behaviour. The selfing rate, as measured by multilocus oligonucleotide DNA fingerprinting, increased with flower number and ranged from 0% to 70%. Flowers on large plants received an equal number of visits from bumblebees as flowers on small plants. On large plants more flowers in a row were visited, inducing geitonogamy. The overall relationship between selfing rate and number of flowers can be explained by pollen dynamics and pollinator behaviour without invoking postpollination processes such as differential pollen tube growth and abortion.
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Geographical variation in threshold size for flowering in Cynoglossum Officinale
Acta Botanica Neerlandica, 1993Co-Authors: Renate A. Wesselingh, Tom J De Jong, Peter G. L. Klinkhamer, Marinke J. Van Dijk, Els G. M. SchlatmannAbstract:We investigated variation in two traits that determine generation time, cold- and size-requirement for flowering, within and among EuroPean populations for the monocarpic perennial Cynoglossum Officinale. When grown in an experimental garden in Leiden, no annual individuals were found among plants originating from 22 locations; all plants were biennial under nutrient-rich growing conditions. In a controlled-environment experiment, in which plants received an artificial cold treatment, flowering probability increased gradually with plant size for plants from two natural populations, signifying a large within-population variation in threshold size for flowering. The relationships between plant size and flowering of these two groups were significantly different: plants from Holkham (England) had much higher threshold sizes than plants from Meijendel (The Netherlands). Three plant groups originating from botanic gardens showed a sharp increase in flowering probability with size, indicating less variation in threshold size. Significant differences existed among all five groups. Results indicate the possibility that natural selection acts upon threshold size for flowering in Cynoglossum Officinale
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Meta‐population dynamics of biennial plants: how to exploit temporary habitats
Plant Biology, 1992Co-Authors: Ed Van Der Meijden, T. J. De Jong, Peter G. L. Klinkhamer, C. A. M. Van WijkAbstract:SUMMARY Extinction of local populations of plants of many biennial plant species has been frequently reported. Survival of these species on the meta-population level implies a balance between extinction and regeneration, either through seed dispersal or from the seedbank. We distinguish between three types of biennials (transient, fugitive and persistent) and review the relation between dynamics of local populations and habitat characteristics, such as disturbance. Some species are safe-site limited whereas other species demonstrate a combination of safe-site and seed limitation. Meta-population dynamics are illustrated with two examples (Senecio jacobaea and Cynoglossum Officinale). We distinguish between patch dynamics (loss and genesis of sites that are suitable for population development) and meta-population dynamics of biennials (population behaviour within and between sites, and dispersal). A hypothesis is developed on the regulation of patch dynamics. Finally we discuss the question: what makes biennials suited for exploiting temporary habitats?
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early flowering in Cynoglossum Officinale l constraint or adaptation
Functional Ecology, 1991Co-Authors: T. J. De Jong, Peter G. L. KlinkhamerAbstract:Of the guild of monocarpic perennials that occur on the sand-dunes of Meijendel (The Netherlands), Cynoglossum Officinale L. is the first species to flower. An experiment was set up in which four groups of plants were grown under controlled conditions and transferred to the field at regular intervals. Group 1 flowered before the natural population of Cynoglossum Officinale, group 2 was in synchrony with the population and groups .3 and 4 flowered later. Plants in grfup 2 produced, on average, 45% more seeds than plants in groups 1 and 3. Plants in group 4, failed to reproduce due to heavy rabbit attack, absence of pollinators and unfavourable weather conditions (night frost). Bumble-bees (Bombus spp.) approached experimental plants most frequently during the natural flowering period and remained frequent visitors until 15 August. After this date no plants of Cynoglossum Officinale were approached. Flowering in Cynoglossum Officinale coincides with the most favourable period of seed production. Key-words: Flowering time, monocarpic perennials, natural selection, pollination
Mahesh K. Upadhyaya - One of the best experts on this subject based on the ideXlab platform.
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Allelopathic Influence of Houndstongue (Cynoglossum Officinale) and Its Modification By UV-B Radiation
Weed Technology, 2008Co-Authors: Nancy H. Furness, Barbara Adomas, Qiujie Dai, Mahesh K. UpadhyayaAbstract:Influence of aqueous leaf extracts, leaf residue, and leached-leaf residue of houndstongue, a noxious rangeland weed, on seedling emergence of forage grasses was studied. Ultraviolet-B (UV-B) effects during houndstongue growth on subsequent germination and growth-inhibitory activity of leaf extracts were investigated. Addition of glasshouse-grown houndstongue leaf extract to mineral soil decreased emergence of crested wheatgrass by 13% and prairie junegrass by 20% at 14 d after sowing. Idaho fescue emergence was unaffected. Incorporation of houndstongue leaf- and leached-leaf residue into soil (0.4 g residue : 20 g soil) delayed emergence of forage grasses. At 14 d after sowing, houndstongue leaf residue spread on the soil surface (0.2 g residue : 20 g soil) tended to inhibit seedling emergence more than leaf residues incorporated into soil. In separate experiments, houndstongue plants were grown at 0, 4, 7, and 11 kJ/m2/d biologically effective UV-B radiation for 6 wk, and leaf extracts (0.5, 1, 2, and 4...
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inhibition of seed germination and seedling growth by hound s tongue Cynoglossum Officinale l seed leachate
Weed Biology and Management, 2005Co-Authors: Abdur Rashid, Brian E. Ellis, Nancy H. Furness, Mahesh K. UpadhyayaAbstract:The leaching of phenolics from decoated seeds, seed coats and pericarps of hound’s-tongue (Cynoglossum Officinale L.), factors affecting leaching, and seed germination and seedling growth inhibitory activities of the leachate were investigated. Embryonic axes and cotyledons contained a large amount of methanol-soluble phenolic substances. Decoated seeds released phenolics into an aqueous incubation medium and this solution was capable of inhibiting root elongation of several grassy and broadleaf species, but not of hound’s-tongue. The leachate and the phenolic fraction of the leachate inhibited germination of bluebunch wheatgrass (Pseudoroegnaria spicata (Pursh) A. Love [syn. Agropyron spicatum (Pursh) Scribn. and J. G. Sm.]). The non-phenolic fraction of the leachate did not inhibit seed germination or root and shoot elongation of bluebunch wheatgrass. Low oxygen and an increasing temperature significantly increased the amount of phenolic substances leached from decoated seeds. Increased leaching of phenolic substances related to an increasing temperature was associated with the loss of seed viability. Further investigation of the role of water-extractable hound’s-tongue seed phenolics in the interaction of this species with its biotic environment under field conditions is needed to determine the ecological significance of these findings.
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Inhibition of seed germination and seedling growth by hound’s‐tongue (Cynoglossum Officinale L.) seed leachate
Weed Biology and Management, 2005Co-Authors: Abdur Rashid, Brian E. Ellis, Nancy H. Furness, Mahesh K. UpadhyayaAbstract:The leaching of phenolics from decoated seeds, seed coats and pericarps of hound’s-tongue (Cynoglossum Officinale L.), factors affecting leaching, and seed germination and seedling growth inhibitory activities of the leachate were investigated. Embryonic axes and cotyledons contained a large amount of methanol-soluble phenolic substances. Decoated seeds released phenolics into an aqueous incubation medium and this solution was capable of inhibiting root elongation of several grassy and broadleaf species, but not of hound’s-tongue. The leachate and the phenolic fraction of the leachate inhibited germination of bluebunch wheatgrass (Pseudoroegnaria spicata (Pursh) A. Love [syn. Agropyron spicatum (Pursh) Scribn. and J. G. Sm.]). The non-phenolic fraction of the leachate did not inhibit seed germination or root and shoot elongation of bluebunch wheatgrass. Low oxygen and an increasing temperature significantly increased the amount of phenolic substances leached from decoated seeds. Increased leaching of phenolic substances related to an increasing temperature was associated with the loss of seed viability. Further investigation of the role of water-extractable hound’s-tongue seed phenolics in the interaction of this species with its biotic environment under field conditions is needed to determine the ecological significance of these findings.
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ROLE OF SEED COAT IN REGULATION OF SEED DORMANCY IN HOUNDSTONGUE (Cynoglossum Officinale)
Weed Science, 1998Co-Authors: Elisa Stabell, Mahesh K. Upadhyaya, Brian E. EllisAbstract:Brian E. Ellis University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 To understand the role of the seed coat in regulation of houndstongue seed dormancy, the effects of manipulation of seed coat integrity on seed germination and 02 uptake were studied. The results suggest that the seed coat of this weed regulates dormancy in part by interfering with the diffusion of 02 to the embryo. Scanning electron microscopy showed a network of ridges on the seed coat surface that were partially dissolved following 1.5 min of sulphuric acid scarification. Mechanical scarification removed fragments of the seed coat surface. Both scarification treatments stimulated seed germination. Supply of an elevated level of 02 also stimulated seed germination. 02 uptake by seeds imbibed in O2-saturated water was 150% higher than that for seeds imbibed in air-saturated water. Although all treatments that stimulated seed germination also stimulated 02 uptake, there was a lack of a consistent, quantitative relationship between increases in 02 uptake and seed germination in various experiments. This suggests that limitation of 02 availability to the embryo is not the only factor involved in regulation of houndstongue seed dormancy by the seed coat. Mechanical restriction of embryo expansion by the seed coat may also be important. Methanol-insoluble phenolics constituted < 1% of the total phenolic pool in the embryo. Their potential oxidation could not account for more than a small fraction of the previously reported massive stimulation of 02 uptake by the embryo upon decoating. The present 02 uptake and seed germination studies indicate that not all of the large increase in 02 uptake following decoating is essential for houndstongue seed germination.
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development of seed coat imposed dormancy during seed maturation in Cynoglossum Officinale
Physiologia Plantarum, 1996Co-Authors: E. Stabell, Mahesh K. Upadhyaya, Brian E. EllisAbstract:The relationship between seed phenolics and appearance of seed coat-imposed dormancy during seed development in Cynoglossum Officinale L. was studied. Up to 24 days after anthesis, seeds failed to germinate upon imbibition in Petri dishes at 25°C. At 44 days after anthesis, seeds were fully germinable ; removal of seed coats did not improve their germination or O 2 uptake. At 72 days after anthesis, mature seeds at the base of the cyme did not germinate unless their coats were removed. Removal of seed coat also stimulated O 2 uptake at this harvest date. The methanol-soluble phenolic content of the seeds increased during the early stages of seed development, in both the seed coat and the embryo. As seed development continued, the methanol-soluble phenolic content of the embryo stabilized, but that of the seed coat declined. This decline was associated with an increase in the thioglycolic acid-soluble phenolics, presumably lignins, in the seed coat. These results suggest that polymerization of methanol-soluble phenolics into lignins in the seed coat during later stages of seed development renders the seed coat of C. Officinale impermeable to O 2 , and thus keeps the seed dormant.
