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  • 1
    Electronic Resource
    Electronic Resource
    Impact of overgrazing on seed predation by rodents in the Thar desert, northwestern India (1995)
    Springer
    Ecological research 10 (1995), S. 217-221 
    Details
    ISSN: 1440-1703
    Keywords: desert rodents ; overgrazing ; seed predation ; succession ; Thar desert
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We compared the vegetation structure, rodent density and seed loss rate between protected and disturbed sites affected from grazing by cattle, goats and sheep, in the Thar desert of India. A perennial tussocky grassLasiurus sindicus Hent. was largely dominant in the protected site, whileL. sindicus was rare and replaced by undershrub speciesAerva pseudotomentosa Blatt. & Halb. andCrotalaria burbira Buch.-Ham. in the overgrazed site. In the grazed site, plant coverage was low, but the density of rodent burrows and the frequency of rodent captures were significantly high as compared to the protected site. Corresponding with the density of desert rodents, seed predation was significantly higher in the grazed site than in the protected site. These results suggest that overgrazing by large mammals has strong effects on plant succession by altering not only the species composition and abundance of plant community, but also the habitat suitability for seed-eating rodents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02347944
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  • 2
    Electronic Resource
    Electronic Resource
    Ecological significance of the aerial seed pool of a desert lignified annual, Blepharis sindica (Acanthaceae) (1998)
    Springer
    Plant ecology 135 (1998), S. 177-184 
    Details
    ISSN: 1573-5052
    Keywords: Aerial seed pool ; Blepharis sindica ; Desert ; Discontinuous seed release ; Germination ; Lignified annual ; Seed predation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Reproductive traits of a lignified annual plant, Blepharis sindica were studied in relation to the formation of an 'aerial seed pool' on dead plants in an arid grassland in the Thar Desert of northwestern India. The dead plants remained standing on the soil surface and retained fruits for more than one year. Aerial seed pools developed about 6 cm above the ground. There were no seed pools on or below the ground surface. Only 5.7% of seeds died on dead plants because of insect predation or fungi infection during one year. Seed release was cued by rainfall, and a fraction of seeds on the aerial seed pools was released in each rainfall event. After 13 rainfall events during the monsoon season, 25% of seeds was still retained on the plants. Seed predation on the ground surface was intensive; all cones placed on the soil surface were removed within four days, and 97% of fruits were removed within 10 days. Fifty percent of seeds germinated within 3.5 h, and there were no differences in viability and time required for germination between first year seeds and older seeds. The results indicate that the aerial seed-holding on dead plants is an available way to avoid seed predation in harsh desert environments where seed predation is intense and favorable periods for growth are temporally limited and unpredictable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009713512472
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of seed release timing on plant life-history and seed production in a population of a desert annual, shape Blepharis sindica (Acanthaceae) (1998)
    Springer
    Plant ecology 136 (1998), S. 195-195 
    Details
    ISSN: 1573-5052
    Keywords: Desert annual ; Fluctuating environments ; Seed release ; Thar Desert
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Growth, phenology, survivorship, and seed production were observed in a population of a desert annual, Blepharis sindica, with reference to the variation in the timing of seedling emergence. The population consisted of several cohorts induced by rain-cued seed release within a growing season. The fate of 100 individuals of six cohorts was monitored throughout the growing season. Earlier-established cohorts had significantly larger plant sizes and higher reproductive outputs than later cohorts. The time and duration of each phenological stage varied among the cohorts, and they were also influenced by plant size. Mortalities at the seedling stage, vegetative stage, and reproductive stage increased with the delay of seed release. Seed release was concentrated in the early growing season. Fecundity was highest in the earliest cohort and decreased monotonically in later cohorts. The results suggested that even in temporally varying environments, the superiority of early emergent plants was evident. The seed release patterns in temporally fluctuating desert environments are discussed as a compromise between 'diversified bet-hedging' and an optimal timing for maximizing the reproductive success in a growing season.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009780605806
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  • 4
    Electronic Resource
    Electronic Resource
    BMPs induce direct bone formation in ectopic sites independent of the endochondral ossification in vivo (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 236 (1993), S. 373-380 
    Details
    ISSN: 0003-276X
    Keywords: Cartilage ; Intramembranous ossification ; Collagen ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Bone formation in vivo occurs via two major processes, one of which depends on pre-existing cartilage, and the other does not. Bone morphogenetic proteins (BMPs) have been suggested to induce cartilage formation from non-skeletogenic mesenchymal cell population, which results in osteogenesis through the endochondral sequence. In the present study we examined if BMPs could cause direct bone formation independent of pre-existing cartilage using bovine fibrous collagen membrane (FCM) as a carrier for BMPs. Bovine metatarsal bone was extracted in 4 M guanidine HCl and BMPs were partially purified through the hydroxyapatite chromatography and the Heparin-Sepharose CL6B chromatography. The carrier was loaded with BMPs and then implanted in Wistar rats subcutaneously. The implants were fixed together with surrounding tissue every week after implantation and processed for von Kossa stain, immunohistochemistry, and electron microscopy. The phenotypes of bone and cartilage were identified histologically and immunohistochemically using antibodies against type I and type II collagen. Cartilage and bone were independently induced by 2 weeks. The bone formed directly on the collagen substrate of FCM without pre-existing cartilage. Calcification occurred in the carrier as well as the cartilage and bone matrix. The present study suggests that the BMPs induce osteogenesis in vivo independent of the endochondral sequence. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092360211
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