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Showing papers on "Seedling published in 2004"


Journal ArticleDOI
TL;DR: While large-seeding species do have a survival advantage over small-seeded species during seedling establishment, the available evidence suggests that advantages must also accrue during other stages in the life cycle.
Abstract: Summary 1Large-seeded species have long been known to have higher survivorship during establishment than small-seeded species. Here, we assessed the size of this advantage by compiling published data on survival through seedling emergence, seedling establishment and sapling establishment. 2We found no relationship between seed mass and survival through the transition from viable seed in or on the soil to newly emerged seedlings (P = 0.47, n = 33 species). 3Synthesis of data from experimental studies on the advantages of large-seeded species establishing under particular hazards (such as shade, drought or herbivory) confirmed that seedlings of large-seeded species perform better than those of small-seeded species in most situations. However, the magnitude of this advantage was not sufficient to counterbalance the greater number of seeds produced by small-seeded species m−2 of canopy outline year−1. 4Synthesis of data from field studies of populations under natural conditions also showed that large-seeded species have higher survival through early seedling establishment than small-seeded species (P = 0.006, n = 112 species). However, the magnitude of this advantage would only be sufficient to counterbalance the greater number of seeds produced by small-seeded species m−2 of canopy outline year−1 if mortality continued at the same rate for some time. 5The time required for a species with 10-fold larger seeds to recoup the advantage gained by a smaller-seeded species during seed production ranged from 8.8 weeks for the smallest seeded species in the data set, up to an implausible 4.2 years for the largest-seeded species. Thus, while large-seeded species do have a survival advantage over small-seeded species during seedling establishment, the available evidence suggests that advantages must also accrue during other stages in the life cycle. One possibility is that the greater seed production of small-seeded species (m−2 of canopy outline year−1) is partly offset by larger canopies and longer reproductive life spans in large-seeded species.

844 citations


Journal ArticleDOI
TL;DR: It is demonstrated that a primary function of tocopherols in plants is to limit nonenzymatic lipid oxidation during seed storage, germination, and early seedling development, and the vte mutant phenotypes explain the strong selection for retention of toCopherol biosynthesis during the evolution of seed-bearing plants.
Abstract: Tocopherols (vitamin E) are lipophilic antioxidants synthesized by all plants and are particularly abundant in seeds. Despite cloning of the complete suite of tocopherol biosynthetic enzymes and successful engineering of the tocopherol content and composition of Arabidopsis thaliana leaves and seeds, the functions of tocopherols in plants have remained elusive. To address this issue, we have isolated and characterized two VITAMIN E loci (VTE1 and VTE2) in Arabidopsis that when mutated result in tocopherol deficiency in all tissues. vte1 disrupts tocopherol cyclase activity and accumulates a redox-active biosynthetic intermediate, whereas vte2 disrupts homogentisate phytyl transferase activity and does not accumulate pathway intermediates. Mutations at either locus cause significantly reduced seed longevity compared with the wild type, indicating a critical role for tocopherols in maintaining viability during quiescence. However, only vte2 mutants exhibited severe seedling growth defects during germination and contained levels of lipid hydroperoxides and hydroxy fatty acids elevated up to 4- and 100-fold, respectively, relative to the wild type. These data demonstrate that a primary function of tocopherols in plants is to limit nonenzymatic lipid oxidation during seed storage, germination, and early seedling development. The vte mutant phenotypes also explain the strong selection for retention of tocopherol biosynthesis during the evolution of seed-bearing plants.

581 citations


Journal ArticleDOI
TL;DR: The results show that in this species the potential for germination is largely programmed during the seed maturation process, being capable of using mRNAs stored during development and germinating seeds can recapitulate at least part of the seedmaturation program.
Abstract: To investigate the role of stored and neosynthesized mRNAs in seed germination, we examined the effect of α-amanitin, a transcriptional inhibitor targeting RNA polymerase II, on the germination of nondormant Arabidopsis seeds. We used transparent testa mutants, of which seed coat is highly permeable, to better ascertain that the drug can reach the embryo during seed imbibition. Even with the most permeable mutant (tt2-1), germination (radicle protrusion) occurred in the absence of transcription, while subsequent seedling growth was blocked. In contrast, germination was abolished in the presence of the translational inhibitor cycloheximide. Taken together, the results highlight the role of stored proteins and mRNAs for germination in Arabidopsis and show that in this species the potential for germination is largely programmed during the seed maturation process. The α-amanitin-resistant germination exhibited characteristic features. First, this germination was strongly slowed down, indicating that de novo transcription normally allows the synthesis of factor(s) activating the germination rate. Second, the sensitivity of germination to gibberellic acid was reduced 15-fold, confirming the role of this phytohormone in germination. Third, de novo synthesis of enzymes involved in reserve mobilization and resumption of metabolic activity was repressed, thus accounting for the failure in seedling establishment. Fourth, germinating seeds can recapitulate at least part of the seed maturation program, being capable of using mRNAs stored during development. Thus, commitment to germination and plant growth requires transcription of genes allowing the imbibed seed to discriminate between mRNAs to be utilized in germination and those to be destroyed.

393 citations


Journal ArticleDOI
TL;DR: Processes controlling seedling establishment in these southern Scots pine forests differ sharply from those operating in its main distribution area, and may contribute to an understanding of the role of environmental conditions in the balance between competition and facilitation, and assist in forecasting plant regeneration responses to global climate change.
Abstract: Summary 1 We analyse the factors controlling seedling establishment of Scots pine at its southernmost geographical limit (southern Spain), by monitoring emergence, survival and growth for up to 4 years in the microhabitats to which seeds are dispersed Naturally established seedlings were monitored in two mountain ranges, and experimental sowings were performed both in woodlands and in adjacent successional shrublands into which the forest could expand 2 Emergence was high in all microhabitats, although it was highest under the canopy of shrubs Overall survival was low, with c 90% of seedlings dying in the first growing season ( c 98% after several growing seasons) Survival differed among microhabitats, being highest under shrubs and extremely low (or zero) under pines or in bare soil 3 Seedling growth was the highest in areas of bare soil, intermediate under shrubs, and very low under pines 4 Establishment under pines was prevented by both mortality and poor performance, and good performance cannot counteract high mortality in the open Shrubs, however, acted as nurse plants, buffering summer drought without reducing radiation to levels critical for growth, and protecting seedlings from ungulate trampling, hail and frost heave 5 Patterns of recruitment were similar for woodland stands and successional shrublands In addition, patterns of survival for naturally established seedlings were similar to those of seedlings originating from experimental sowings 6 Juveniles were positively associated with shrubs but negatively with bare soil or areas below pine canopies The facilitative effect of shrubs on seedling survival therefore changes the spatial pattern of recruitment from that determined by germination 7 Overall, processes controlling seedling establishment in these southern Scots pine forests differ sharply from those operating in its main distribution area The comparison among contrasting geographical ranges may contribute to an understanding of the role of environmental conditions in the balance between competition and facilitation, and assist in forecasting plant regeneration responses to global climate change

390 citations


Journal ArticleDOI
TL;DR: It is concluded that scatter-hoarding rodents can select for both large seed crops and large seeds, which may reinforce mast seeding.
Abstract: Many tree species that depend on scatter-hoarding animals for seed dispersal produce massive crops of large seeds at irregular intervals. Mast seeding and large seed size in these species have been explained as adaptations to increase animal dispersal and reduce predation. We studied how seed size and seed abundance simultaneously influenced seed dispersal and predation by scatter-hoarding rodents in the large-seeded rain forest tree Carapa procera (Meliaceae) in French Guiana. We individually tracked the fates of 3000 seeds, using remote video monitoring and thread-marking. Seed size was manipulated by broadly varying intraspecific seed mass, whereas effects of seed abundance were examined by tracking seeds in three seed-rich years and two seed-poor years. The hypotheses, that seed mass and seed abundance both enhance dispersal success and that seed abundance reinforces the effect of seed mass, were supported by the results. Most seeds were removed by the scatter-hoarding rodent red acouchy (Myoprocta acouchy) and subsequently were buried in scattered, single-seeded caches up to distances >100 m. Seeds that were not removed failed to establish seedlings. Seed removal was slower, pre-removal seed predation was greater, and seed dispersal was less far in seed-rich years than in seed-poor years, suggesting poorer dispersal under seed abundance. However, this was more than counterbalanced by a disproportionally greater survival of cached seeds in seed-rich years. The per capita probability of seed survival and seedling establishment was at least 4½ times greater under seed abundance. Large seeds were removed faster, were more likely to be scatter-hoarded, and were dispersed farther away than smaller ones, resulting in a higher probability of seedling establishment for larger seeds. Size discrimination was greater under seed abundance, albeit only during seed removal. Overall, large seeds shed in rich years had the highest probability of seedling establishment. Hence, both larger seed size and greater seed abundance stimulate rodents to act more as dispersers and less as predators of seeds. We conclude that scatter-hoarding rodents can select for both large seed crops and large seeds, which may reinforce mast seeding.

369 citations


Journal ArticleDOI
TL;DR: The key issue is that variance in survival of plant life-history stages, and therefore the importance of dispersal, differs greatly among and within plant communities.
Abstract: A profusion of fruit forms implies that seed dispersal plays a central role in plant ecology, yet the chance that an individual seed will ultimately produce a reproductive adult is low to infinitesimal. Extremely high variance in survival implies that variations in fruit production or transitions from seed to seedling will contribute little to population growth. The key issue is that variance in survival of plant life-history stages, and therefore the importance of dispersal, differs greatly among and within plant communities. In stable communities of a few species of long-lived plants, variances in seed and seedling survival are immense, so seed-to-seedling transitions have little influence on overall population dynamics. However, when seedlings in different circumstances have very different chances of survival—in ecological succession, for example, or when dispersed seeds escape density-dependent mortality near parent trees—the biased survival of dispersed seeds or seedlings in some places rath...

357 citations


Journal ArticleDOI
TL;DR: The general assumption that offspring fitness is a fixed positive function of seed size needs to be reconsidered for some systems, and the existence of conflicting selection might explain the occurrence of an optimal seed size in some plant species without invoking a seed number‐size trade‐off.
Abstract: Most theoretical treatments of the evolutionary ecology of offspring size assume a simple and direct effect of investment per offspring on offspring fitness. In this paper I experimentally determine the relationship between seed mass and several main fitness components of the oak Quercus ilex, to estimate phenotypic selection acting on seed mass during the early life cycle and to discover any potential selective conflicts occurring between different stages from dispersal to establishment. I found a positive effect of acorn size on most fitness components related to seedling establishment. Large size increased germination rate and seedling survival, accelerated germination timing, and enhanced seedling growth. Nevertheless, there was also a direct negative effect of acorn size on survival to predation, because large acorns were highly preferred by the main postdispersal seed predators at the study site, wild boars and wood mice. Because of the low probability of escape from predation, the fitness of large acorns estimated on this component was significantly lower than the fitness of smaller acorns. Therefore, seed size affected fitness in two different ways, yielding opposing and conflicting selective forces. These findings suggest that the general assumption that offspring fitness is a fixed positive function of seed size needs to be reconsidered for some systems. The existence of conflicting selection might explain the occurrence of an optimal seed size in some plant species without invoking a seed number-size trade-off.

339 citations


Journal ArticleDOI
TL;DR: The reduction in Na uptake together with a concomitant increase in P, N and Mg absorption and high chlorophyll content in mycorrhizal plants may be important salt-alleviating mechanisms for plants growing in saline soil.
Abstract: A field experiment was conducted to examine the effect of the arbuscular mycorrhizal fungus Glomus macrocarpum and salinity on growth of Sesbania aegyptiaca and S. grandiflora. In the salt-stressed soil, mycorrhizal root colonisation and sporulation was significantly higher in AM-inoculated than in uninoculated plants. Mycorrhizal seedlings had significantly higher root and shoot dry biomass production than non-mycorrhizal seedlings grown in saline soil. The content of chlorophyll was greater in the leaves of mycorrhiza-inoculated as compared to uninoculated seedlings. The number of nodules was significantly higher in mycorrhizal than non-mycorrhizal plants. Mycorrhizal seedling tissue had significantly increased concentrations of P, N and Mg but lower Na concentration than non-mycorrhizal seedlings. Under salinity stress conditions both Sesbania sp. showed a high degree of dependence on mycorrhizae, increasing with the age of the plants. The reduction in Na uptake together with a concomitant increase in P, N and Mg absorption and high chlorophyll content in mycorrhizal plants may be important salt-alleviating mechanisms for plants growing in saline soil.

334 citations


Journal ArticleDOI
TL;DR: 24-epiBL treatment considerably alleviated oxidative damage that occurred under NaCl-stressed conditions and improved seedling growth in part under salt stress in sensitive IR-28 seedlings.
Abstract: The effects of 24-epibrassinolide (24-epiBL) on seedling growth, antioxidative system, lipid peroxidation, proline and soluble protein content were investigated in seedlings of the salt-sensitive rice cultivar IR-28. Seedling growth of rice plants was improved by 24-epiBL treatment under salt stress conditions. When seedlings treated with 24-epiBL were subjected to 120 mM NaCl stress, the activities of superoxide dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6) and glutathione reductase (EC 1.6.4.2) did not show significant difference, whereas the activity of ascorbate peroxidase (EC 1.11.1.11) significantly increased. Increased activity of peroxidase (EC 1.11.1.7) under NaCl stress showed remarkable decrease in the 24-epiBL+NaCl-applied group. Lipid peroxidation level significantly increased under salt stress but decreased with 24-epiBL application revealing that less oxidative damage occurred in this group (24-epiBL+NaCl). In addition, increased proline content in the NaCl-applied group was decreased by 24-epiBL application in the 24-epiBL+NaCl-applied group. Soluble protein content was increased by 24-epiBL application even under NaCl stress, being also higher than control conditions (no 24-epiBL or NaCl treatment). 24-epiBL treatment considerably alleviated oxidative damage that occurred under NaCl-stressed conditions and improved seedling growth in part under salt stress in sensitive IR-28 seedlings.

306 citations


Journal ArticleDOI
TL;DR: Results indicate that AMF promote seedling establishment by integrating emerging seedlings into extensive hyphal networks and by supplying nutrients to the seedlings, and act as a symbiotic support system that promotes seedlings establishment and reduces recruitment limitation in grassland.
Abstract: Recruitment of new seedlings into the vegetation is essential for maintaining species rich plant communities. Hence it is of pivotal importance to understand factors determining seedling recruitment. Here it is tested whether arbuscular mycorrhizal fungi (AMF) promote seedling recruitment in perennial grassland communities. Seeds of four plant species (two grasses and two forbs) were added to patches within 1-year old grassland microcosms that were inoculated with different AMF taxa or to control microcosms that were not inoculated. The seedlings grew larger and obtained more phosphorus when AMF were present. Moreover, the seedlings obtained different amounts of phosphorus in microcosms inoculated with different AMF taxa. The results indicate that AMF promote seedling establishment by integrating emerging seedlings into extensive hyphal networks and by supplying nutrients to the seedlings. AMF, thus, act as a symbiotic support system that promotes seedling establishment and reduces recruitment limitation in grassland.

233 citations


Journal ArticleDOI
TL;DR: In this article, four crop plant species (sweet corn, Zea may; wheat, Triticum aestivum; cucumber, Cucumis sativus; and sorghum, Sorghum bicolor) were tested to assess an ecotoxicity in cadmium-amended soils.

Journal ArticleDOI
TL;DR: It is found that spatially aggregated seed deposition strongly influenced the spatial structure of later stages of a vertebratedispersed rain forest tree, Virola calophylla, and the clumped dispersion at sleeping and parental sites persisted to the seedling/sapling stage.
Abstract: The initial spatial pattern of seed deposition influences plant population and community structure, particularly when that pattern persists through recruitment. In a vertebratedispersed rain forest tree, Virola calophylla, we found that spatially aggregated seed deposition strongly influenced the spatial structure of later stages. Seed dispersion was clumped, and seed densities were highest underneath V. calophylla females and the sleeping sites of spider monkeys (Ateles paniscus), the key dispersal agent. Although these site types had the lowest per capita seed-to-seedling survival, they had the highest seedling/sapling densities. Conversely, seed and seedling/sapling densities were lowest, and seed survival was highest, at sites of diurnal seed dispersal by spider monkeys. Negative density-dependent and positive distance-dependent seed survival thinned seed clumps. Nonetheless, the clumped dispersion at sleeping and parental sites persisted to the seedling/sapling stage because differences in seed deposition were large enough to offset differences in seed survival among these site types.

Journal ArticleDOI
TL;DR: The chilling tolerance, expressed in cell membrane damage, degree of chilling injury, survival rate, and photosynthesis was enhanced in plants of transgenic lines 2, 3, 4 and 5 as compared with wild type plants, which might play an important role of osmoregulation under stress conditions.

Journal ArticleDOI
TL;DR: Sugar beet progeny lines screened for both high water use efficiency and high sugar yield under drought stress conditions in the field were assessed and seedling characteristics, in addition to other physiological components involved in the seed germination process under specific stress conditions, may be considered for breeding purposes.
Abstract: Sugar beet progeny lines screened for both high water use efficiency and high sugar yield under drought stress conditions in the field were assessed for the rate of seed germination and early seedling growth in water deficit stress, induced by mannitol solutions. Seeds of nine different sugar beet progeny lines were grown in three experimental conditions using filter paper, perlite and water agar as substrate. Three levels of 0.0, 0.2 and 0.3 m mannitol concentrations were applied in each experiment. A factorial design was used with three replications. Germination percentage was determined in all experiments. Seedling growth parameters such as cotyledon fresh weight, cotyledon dry weight, root fresh weight, root dry weight (RDW) and root length (RL) were measured experimentally. Abnormality was only recorded in the filter paper experiment. The results showed that drought stress could be simulated by mannitol solution and significant differences were found between stress levels for seedling characteristics. Distinct genetic variances were found among progeny lines with respect to germination and early seedling growth characteristics, except for cotyledons and RDW. Seedling growth and germination rates severely declined at the highest concentration of mannitol. The rate of abnormality was increased progressively at the germination stage with an increase in mannitol concentration but it was more pronounced in the drought-susceptible progeny lines. The highest values of relative germination % and relative growth % of RL were obtained for the most tolerant line. In conclusion, seedling characteristics, in addition to other physiological components involved in the seed germination process under specific stress conditions, may be considered for breeding purposes.

Journal ArticleDOI
TL;DR: Salinity decreased seedling fresh weight and germination percentage, spinach being the exception, and the ratio (Spd + Spm)/Put increased with salinity in all studied species, which would infer increased tolerance to salinity.

Journal ArticleDOI
TL;DR: Results suggest possible different behaviors of cultivars differing in salt tolerance with respect to germination, seedling vigor, plant growth, water content (WC) and Na + /K + contents.

Journal ArticleDOI
01 Jun 2004-Ecology
TL;DR: Results indicate that ECM fungi associated with established willow shrubs are essential in facilitating seedling establishment of successional plant species in the early successional volcanic desert.
Abstract: Ectomycorrhizal (ECM) fungi are symbiotic microorganisms that can significantly improve the water and nutrient uptake of host plants. With reference to ECM fungi, we studied the effects of established shrubs on the subsequent seedling establishment of three woody plant species in a volcanic desert on Mt. Fuji, Japan, during early primary succession. Salix reinii, an alpine dwarf willow, is the pioneer ECM plant at this research site, and many ECM fungi have colonized established willow shrubs. ECM formation was found to be high on S. reinii seedlings that had been transplanted near established willow shrubs. The growth and nitrogen content of the seedlings increased significantly with the numbers of associated ECM fungal species and ECM root tips. ECM formation on transplanted seedlings of Betula ermanii and Larix kaempferi, two subsequent successional tree species, was also higher near the established willow shrubs. Molecular identification showed that almost all of the ECM fungi on transplanted seedlings of the three plant species were of the same species as those observed on the established willow shrubs. These results indicate that ECM fungi associated with established willow shrubs are essential in facilitating seedling establishment of successional plant species in the early successional volcanic desert.

Journal ArticleDOI
TL;DR: The results clearly demonstrated that Prosopis is equipped with a number of biological characteristics that foster its rapid invasion of new areas and is a powerful noxious invader as can be evidenced from its rampant invasion in the study site and elsewhere in the tropics.

Journal ArticleDOI
TL;DR: The results suggest that texasweed seed is capable of germinating and surviving in a variety of climatic and edaphic conditions, and that flooding is not a viable management option for emerged plants oftexasweed.
Abstract: Field, laboratory, and greenhouse experiments were conducted to determine the seed production potential and effect of environmental factors on germination, emergence, and survival of texasweed. Texasweed produced an average of 893 seed per plant, and 90% were viable. Seed exhibited dormancy, and prechilling did not release dormancy. Percent germination ranged from 56% for seed subjected to no prechilling to 1% for seed prechilled at 5 C for 140 d. Seed remained viable during extended prechilling conditions, with 80% of seed viable after 140 d of prechilling. Texasweed seed germinated over a range of 20 to 40 C, with optimum germination (54%) occurring with a fluctuating 40/30 C temperature regime. Seed germinated with fluctuating 12-h light/dark and constant dark conditions. Texasweed seed germinated over a broad range of pH, osmotic potential, and salt concentrations. Seed germination was 31 to 62% over a pH range from 4 to 10. Germination of texasweed ranged from 9 to 56% as osmotic potential d...

Journal ArticleDOI
TL;DR: Experimental results showed that TMS treatments greatly promoted seedling growth and improved seedling quality.
Abstract: The roots of 200 one-year-old Changbai Larch (Larix olgensis) seedlings were soaked for 6 hours at the TMS concentrations of 2000, 1000, 500, 250, 125, and 62 μL·L−1 Mean seedling height, root collar diameter, main root length and number of lateral roots were measured every 15 days during growing season from May 30 to Oct 20 Experimental results showed that TMS treatments greatly promoted seedling growth and improved seedling quality The treatment by 500 μL·L−1 TMS produced the best result, for which the mean height, root collar diameter, main root length, and the number of lateral roots of seedlings were increased by 425%, 307%, 140%, and 316%, respectively, compared to that of the control seedlings As to seedling quality, grade-I seedling and grade-II seedlings were fifty-fifty, and no grade-III seedlings was found The treatment by 500 μL·L−1 TMS resulted in the highest chlorophyll concentration

Journal ArticleDOI
01 Feb 2004-Planta
TL;DR: It is reported that glucose delays germination of Arabidopsis thaliana (L.) Heynh seeds at concentrations below those known to inhibit early seedling development and this inhibition acts on embryo growth and is independent of hexokinase (HXK) function.
Abstract: Here we report that glucose delays germination of Arabidopsis thaliana (L.) Heynh. seeds at concentrations below those known to inhibit early seedling development. This inhibition acts on embryo growth and is independent of hexokinase (HXK) function. Hormones and hormone inhibitors were applied to the germination media and several hormone biosynthesis and signalling mutants were tested on glucose media to investigate a possible role of abscisic acid (ABA), gibberellin and ethylene in the glucose-induced germination delay. Results indicate that the germination inhibition by glucose cannot be antagonized by ethylene or gibberellin and is independent of the HXK1/ABA/ABI4 signalling cascade. These findings suggest that there is a separate regulatory pathway independent of ABI2/ABI4/ABI5. Thus, in a relatively short time frame sugars utilize different signalling cascades to inhibit germination and post-germination growth, underlining the complexity of sugar responses.

Journal ArticleDOI
TL;DR: A large number of independently inherited loci suitable for the improvement of early seedling growth through better seed vigour and/or a higher rate of photosynthesis are found.
Abstract: The improvement of early vigour is crucial for the adaptation of maize (Zea mays L.) to the climatic conditions of central Europe and the northern Mediterranean, where early sowing is an important strategy for avoiding the effect of summer drought. The objectives of this study were to identify quantitative trait loci (QTL) controlling cold-related traits and to investigate the relationships among them. A set of 168 F2:4 families of the Lo964 × Lo1016 cross was grown in a sand–vermiculite substrate at 15/13°C (day/night) until the one-leaf stage. Twenty QTL were identified for the four shoot and two seed traits examined. Analysis of root weight and digital measurements of the length and diameter of primary and seminal roots led to the identification of 40 QTL. The operating efficiency of photosystem II (ΦPSII) was related to seedling dry weight at both the phenotypic and genetic level (r=0.46, two matching loci, respectively) but was not related to root traits. Cluster analysis and QTL association revealed that the different root traits were largely independently inherited and that root lengths and diameters were mostly negatively correlated. The major QTL for root traits detected in an earlier study in hydroponics were confirmed in this study. The length of the primary lateral roots was negatively associated with the germination index (r=−0.38, two matching loci). Therefore, we found a large number of independently inherited loci suitable for the improvement of early seedling growth through better seed vigour and/or a higher rate of photosynthesis.

Journal ArticleDOI
TL;DR: The results emphasize the importance of looking beyond a single type of plant-animal interaction to incorporate potential effects of interacting interactions and how seed size affects the interaction between seeds, dung beetles, and rodents.
Abstract: Seeds dispersed by tropical, arboreal mammals are usually deposited singly and without dung or in clumps of fecal material. After dispersal through defecation by mammals, most seeds are secondarily dispersed by dung beetles or consumed by rodents. These post-dispersal, plant-animal interactions are likely to interact themselves, as seeds buried by dung beetles are less likely to be found by rodents than unburied seeds. In a series of three experiments with seeds of 15 species in central Amazonia (Brazil), we determined (1) how presence and amount of dung associated with seeds influences long-term seed fate and seedling establishment, (2) how deeply dung beetles bury seeds and how burial depth affects seedling establishment, and (3) how seed size affects the interaction between seeds, dung beetles, and rodents. Our overall goal was to understand how post-dispersal plant-animal interactions determine the link between primary seed dispersal and seedling establishment. On average, 43% of seeds surrounded by dung were buried by dung beetles, compared to 0% of seeds not surrounded by dung ( n=2,156). Seeds in dung, however, tended to be more prone than bare seeds to predation by rodents. Of seeds in dung, probability of burial was negatively related to seed size and positively related to amount of dung. Burial of seeds decreased the probability of seed predation by rodents three-fold, and increased the probability of seedling establishment two-fold. Mean burial depth was 4 cm (0.5-20 cm) and was not related to seed size, contrary to previous studies. Probability of seedling establishment was negatively correlated with burial depth and not related to seed size at 5 or 10 cm depths. These results illustrate a complex web of interactions among dung beetles, rodents, and dispersed seeds. These interactions affect the probability of seedling establishment and are themselves strongly tied to how seeds are deposited by primary dispersers. More generally, our results emphasize the importance of looking beyond a single type of plant-animal interaction (e.g., seed dispersal or seed predation) to incorporate potential effects of interacting interactions.

Journal ArticleDOI
01 Feb 2004-Ecology
TL;DR: It is suggested that all dominant species in northern hardwood forests can be seed limited at some spatial scale and that results are consistent with “winning by forfeit” scenarios of diversity maintenance in forest ecosystems.
Abstract: Despite increasing evidence of seed limitation in forest ecosystems, data remain sparse on spatial patterns of seed rain at large (>1 ha) spatial scales. We monitored seed rain (28.5 m2) throughout five northern hardwood forest fragments (27 ha sampled across 14-km2 area) in southeastern Michigan over two years. Four fragments were nearest neighbors (300–700 m), yet varied in species composition, providing the opportunity to detect landscape-scale seed exchange. Of the 37 species of woody plants present in the seed rain (98 032 mature seeds), only three (Betula papyrifera, Ostrya virginiana, and Ulmus americana) had widespread seed dispersions within all fragments containing resident sources (seed in >70% of traps in each fragment). Seed dispersions, measured as the percentage of traps within a fragment receiving seed, differed among species using different dispersal vectors with animal-dispersed species arriving in a lower percentage of seed traps than wind-dispersed seeds. At a given source density, seed dispersions increased with decreasing seed mass. Light-seeded, fecund species such as Betula or Tsuga required lower source densities to saturate fragments with seed compared to heavy-seeded species (Acer, Fraxinus, Tilia). Heavy-seeded wind- and animal-dispersed species also displayed the strongest evidence of seed limitation, with seedling presence significantly associated with presence of seed for Carpinus caroliniana, Fagus grandifolia, Prunus avium, and Tilia americana. Of 17 species, landscape-scale seed exchange was detected for only four disturbance-associated species (Acer negundo, Betula papyrifera, Celastrus scandens, Eleaganus umbellata). No exchange was detected for Acer rubrum, Betula alleghaniensis, or Tsuga canadensis, despite broad seed dispersions (>50%) in fragments with resident sources, suggesting the potential for seed limitation for these species at larger spatial scales. Seed encounter probabilities suggest that potential seed competitors often fail to simultaneously colonize microsites. We suggest that all dominant species in northern hardwood forests can be seed limited at some spatial scale and that results are consistent with “winning by forfeit” scenarios of diversity maintenance in forest ecosystems.

Journal ArticleDOI
TL;DR: The results suggest that Methylobacterium inoculation may alter rice susceptibility to R. solani and emphasizes the importance of evaluating induced systemic resistance while studying plant-associated growth promoting bacteria.
Abstract: Pink-pigmented facultatively methylotrophic bacteria (PPFMs), persistent colonizers of plant leaf surfaces, belong to the genus Methrlobacterium and are mostly transmitted through seeds. Plant growth-promoting activity of methylotrophic bacteria and their effects on disease suppression were evaluated on rice under greenhouse conditions. Rice seeds were inoculated with Methylobacterium sp. strain PPFM-Os-07 and seed germination was evaluated in terms of morphometric measurements, seedling growth, rate of germination (R(subscript G)), and seedling vigour index (SVI). Another experiment was carried out to study the induction of pathogenesis-related proteins (PR-proteins) in rice plants that were inoculated with methylotrophic bacteria by seed imbibition or foliar spray. In the third experiment, sixty-day-old rice plants grown in pots were challenge inoculated with Rhizoctonia solani strain TNAU-01. Methylobacterium inoculation promoted seed germination and plant growth. Increased plant height, number of tillers, plant biomass, and grain yield were observed. The average yield increases for seed imbibition and phyllosphere spray were, respectively, 22.1% and 24.3% greater than control. The bacteria also significantly reduced the sheath blight incidence when applied as either bacterial culture through seed imbibition and or phyllosphere spray. The percent disease reduction recorded for seed imbibition alone and for combined applications of seed imbibition and phyllosphere spray were 17.8% and 23.5%. Rice plants sprayed with PPFM-Os-07 strain showed increased presence of PR-proteins and phenolic contents on day 1 after application. Maximum phenylalanine ammonia lyase (PAL) and peroxidase activity on day 4 and β-1,3-glucanase and chitinase activity on day 5 were recorded. The results suggest that Methylobacterium inoculation may alter rice susceptibility to R. solani. This work emphasizes the importance of evaluating induced systemic resistance while studying plant-associated growth promoting bacteria.

Journal ArticleDOI
TL;DR: The effect of microhabitat and seed burial on the main demographic processes operating during the early recruitment of Quercus ilex, such as postdispersal seed predation, seed germination, and seedling emergence, survival and growth is investigated.
Abstract: This study investigates the effect of microhabitat and seed burial on the main demographic processes operating during the early recruitment of Quercus ilex, such as postdispersal seed predation, seed germination, and seedling emergence, survival and growth. The effect of burial was positive over all the processes analysed in this study, since predation rate was lower (63.6% vs. 88%), whereas germination (53.1% vs. 21.8%) and emergence (32.0% vs. 5.5%) were higher for buried acorns. The quality of some microhabitats remained similar throughout the stages and processes studied. Thus, afforestation provided especially suitable microhabitats for oak establishment, since seed predation was lower, while germination, emergence and seedling survival were higher, than in any other microhabitat. By contrast, the quality of some microhabitats, such as open sites and Holm oaks, differed between recruitment stages. Acorns in open sites escaped predation and germinated easily, but most seedlings died due to summer drought. Similarly, although acorns under Holm oaks can germinate and survive drought, they cannot survive to postdispersal predators. This uncoupling results in a post-dispersal change in the spatial distribution of Q. ilex recruits. Furthermore, there were significant interactions between burial and microhabitat for some demographic processes. The recruitment was in afforestations high irrespective of burial, suggesting that burial is not as beneficial in high-quality habitats as it is in lower-quality ones. An accurate understanding of plant recruitment requires the determination not only of the direct effects of limiting factors but also the potential interactions occurring between them.

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TL;DR: Hic acid applied to the plant growth medium at 1000 mg kg−1 concentration increased seedling growth and nutrient contents of plants and enhanced micro-nutrient contents of plant organs, however, high levels of humic acid arrested plant growth or decreased nutrient contents.
Abstract: The effects of calcium and humic acid on seed germination, growth and macro- and micro-nutrient contents of tomato (Lycopersicon esculentum L.) seedlings in saline soil conditions were evaluated. Different levels of humic acid (0, 500, 1000 and 2000 mg kg−1) and calcium (0, 100, 200 and 400 mg kg−1) were applied to growth media treated with 50 mg NaCl kg−1 before sowing seeds. Seed germination, hypocotyl length, cotyledon width and length, root size, shoot length, leaf number, shoot and root fresh weights, and shoot and root dry weights of the plant seedlings were determined. Macro- and micro-nutrient (N, P, K, Ca, Mg, S, Cu, Fe, Mn and Zn) contents of shoot and root of seedlings were also measured. Humic acid applied to the plant growth medium at 1000 mg kg−1 concentration increased seedling growth and nutrient contents of plants. Humic acid not only increased macro-nutrient contents, but also enhanced micro-nutrient contents of plant organs. However, high levels of humic acid arrested plant growth or de...

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TL;DR: The results suggest that A. ursinum influences other herbaceous plants in plant community via soil and volatile compounds which inhibit seed germination and plant growth.

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TL;DR: The results suggest that establishment limitation, i.e. the reduction of growth and survival from seedling to adult, controls species recruitment in highly fertile sites, thereby isolating these communities from the regional species pool.
Abstract: Summary 1 At local spatial scales, species richness tends to fall as productivity rises. Most explanations have focused on increased extinction, but, instead, we test experimentally whether increased soil fertility reduces recruitment. Specifically, we test whether variation in recruitment is due to source limitation, germination limitation or establishment limitation, and how litter accumulation and seed predation contribute to these processes. 2 We established four crossed experimental treatments in a perennial-dominated early successional plant community over 3 years. We added seed of 30 species, manipulated access by selected seed predators, removed litter and added slow release fertilizer at four levels (0, 8, 16 and 32 g N m−2). 3 Species recruitment and richness both decreased with increasing fertility, but, counter to our expectations, we found that neither seed additions nor litter removal could counteract the negative effects of fertilizer. 4 Seed additions increased seedling density at all fertilizer levels, and seed predation appeared to have no influence on seedling densities. In spite of high seedling densities at all fertilizer levels, final stem density declined by 70% as fertilizer increased. A strong stem density–species richness relationship suggests that declines in final stem density caused more than half of the decline in species richness along this fertility gradient. 5 These results suggest that establishment limitation, i.e. the reduction of growth and survival from seedling to adult, controls species recruitment in highly fertile sites. 6 The high degree of recruitment limitation commonly observed in productive habitats suggests that high productivity causes establishment limitation, thereby isolating these communities from the regional species pool. We suggest that such isolation provides a mechanism to explain why the species composition of productive communities exhibits higher variability than the composition of less productive communities within the same regional source pool.

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TL;DR: It is concluded that volatile oil from E. citriodora is phytotoxic and could be utilized as bioherbicide for future weed management programmes and the energy metabolism of the target plants.