Showing papers in "Critical Reviews in Plant Sciences in 2004"
TL;DR: The propensity for wetlands to become dominated by invasive monotypes is arguably an effect of the cumulative impacts associated with landscape sinks, including import of hydrophytes that exhibit efficient growth (high plant volume per unit biomass).
Abstract: Wetlands seem to be especially vulnerable to invasions. Even though ≤6% of the earth's land mass is wetland, 24% (8 of 33) of the world's most invasive plants are wetland species. Furthermore, many wetland invaders form monotypes, which alter habitat structure, lower biodiversity (both number and “quality” of species), change nutrient cycling and productivity (often increasing it), and modify food webs. Wetlands are landscape sinks, which accumulate debris, sediments, water, and nutrients, all of which facilitate invasions by creating canopy gaps or accelerating the growth of opportunistic plant species. These and other disturbances to wetlands, such as propagule influx, salt influx, and hydroperiod alteration, create opportunities that are well matched by wetland opportunists. No single hypothesis or plant attribute explains all wetland invasions, but the propensity for wetlands to become dominated by invasive monotypes is arguably an effect of the cumulative impacts associated with landscape sinks, incl...
843 citations
TL;DR: In this article, the authors describe the importance of plants and soil functions on carbon sequestration, review the mechanisms of SOC sequestration within aggregates under different vegetation and soil management practices, and explain methods of assessing distribution of organic matter in aggregates, and identify knowledge gaps with regards to SOC and soil structural dynamics.
Abstract: Soil and crop management practices have a profound impact on carbon (C) sequestration, but the mechanisms of interaction between soil structure and soil organic C (SOC) dynamics are not well understood. Understanding how an aggregate stores and protects SOC is essential to developing proper management practices to enhance SOC sequestration. The objectives of this article are to: (1) describe the importance of plants and soil functions on SOC sequestration, (2) review the mechanisms of SOC sequestration within aggregates under different vegetation and soil management practices, (3) explain methods of assessing distribution of SOC within aggregates, and (4) identify knowledge gaps with regards to SOC and soil structural dynamics. The quality and quantity of plant residues define the amount of organic matter and thus the SOC pool in aggregates. The nature of plant debris (C:N ratio, lignin content, and phenolic compound content) affects the rate of SOC sequestration. Mechanisms of interaction of aggregate dy...
503 citations
TL;DR: In this article, the authors defined sustainability and sustainable cyclic processes, and quantified the degree of non-renewability of a major biofuel: ethanol produced from industrially grown corn.
Abstract: This article defines sustainability and sustainable cyclic processes, and quantifies the degree of non-renewability of a major biofuel: ethanol produced from industrially grown corn. It demonstrates that more fossil energy is used to produce ethanol from corn than the ethanol's calorific value. Analysis of the carbon cycle shows that all leftovers from ethanol production must be returned back to the fields to limit the irreversible mining of soil humus. Thus, production of ethanol from whole plants is unsustainable. In 2004, ethanol production from corn will generate 8 million tons of incremental CO2, over and above the amount of CO2 generated by burning gasoline with 115% of the calorific value of this ethanol. It next calculates the cumulative exergy (available free energy) consumed in corn farming and ethanol production, and estimates the minimum amount of work necessary to restore the key non-renewable resources consumed by the industrial corn-ethanol cycle. This amount of work is compared with the ma...
388 citations
TL;DR: In this paper, a review of the literature examining the manipulation of microbial populations as linked to agricultural production, and discusses new approaches that involve the precision management of microorganisms in the agro-ecosystem is presented.
Abstract: Historically, agricultural production has relied on practices designed to manage nutrients, water, weeds, and crop diseases. Precision agriculture and integrated pest management programs have gone one step further by recognizing the need to target inputs where they are required in the field. The major objective of these programs has been to minimize adverse environmental impacts of intensive agriculture practices and reduce per unit production costs. This review surveys the literature, examining the manipulation of microbial (primarily bacterial) populations as linked to agricultural production, and discusses new approaches that involve the precision management of microorganisms in the agro-ecosystem. It is proposed that our understanding of plant–soil interactions can be greatly refined through the development of “smart” field technology, where real-time, computer-controlled electronic diagnostic devices can be used to monitor rhizosphere and plant health. We submit that “smart field” generated informati...
355 citations
TL;DR: The responses of potential Brassica crops to soil salinity from the whole plant to the molecular level is highlighted and the role of important organic osmotica such as total soluble sugars, free amino acids, and free proline, which are central to osmotic adjustment, have been discussed.
Abstract: Brassica oilseed species now hold the third position among oilseed crops and are an important source of vegetable oil. The most common Brassica oil-seed crops grown for commercial purposes are rape seeds, (Brassica campestris L. and B. napus L.) and mustards (B. juncea (L.) Czern. & Coss. and B. carinata A.Br.). The other Brassica species such as B. nigra (L.) Koch and B. tournefortii Gouan are grown on a very small scale. Brassica napus, B. juncea, and B. carinata are amphidiploids, whereas B. campestris and B. nigra are diploid. Most of the Brassica species have been categorized as moderately salt tolerant, with the amphidiploid species being the relatively salt tolerant in comparison with the diploid species. Due to the higher salt tolerance of the amphidiploids, it has been suggested that their salt tolerance has been acquired from the A (B. campestris) and C (B. oleracea L.) genomes. However, significant inter- and intraspecific variation for salt tolerance exists within brassicas, which can be explo...
321 citations
TL;DR: Root nodule extensins are a legume-specific family of hydroxyproline-rich glycoproteins targeted into the lumen of the infection thread that may serve to regulate fluid-to-solid transitions in the extracellular matrix.
Abstract: Colonization of host cells by rhizobium bacteria involves the progressive remodelling of the plant–microbial interface. Following induction of nodulation genes by legume-derived flavonoid signals, rhizobium secretes Nod-factors (lipochitin oligosaccharides) that cause root hair deformations by perturbing the growth of the plant cell wall. The infection thread arises as a tubular ingrowth bounded by plant cell wall. This serves as a conduit for colonizing bacterial cells that grow and divide in its lumen. The transcellular orientation of thread growth is controlled by the cytoskeleton and is coupled to cell cycle reactivation and cell division processes. In response to rhizobium infection, host cells synthesize several new components (early nodulins) that modify the properties of the cell wall and extracellular matrix. Root nodule extensins are a legume-specific family of hydroxyproline-rich glycoproteins targeted into the lumen of the infection thread. They have alternating extensin and arabinogalactan (A...
305 citations
TL;DR: This review evaluates evidence of the impact of uncomposted plant residues, composts, manures, and liquid preparations made from composts (compost extracts and teas) on pest and disease incidence and severity in agricultural and horticultural crop production.
Abstract: This review evaluates evidence of the impactof uncomposted plant residues, composts, manures, and liquid preparations made from composts (compost extracts and teas) on pest and disease incidence and severity in agricultural and horticultural crop production. Most reports on pest control using such organic amendments relate to tropical or arid climates. The majority of recent work on the use of organic amendments for prevention and control of diseases relates to container-produced plants, particularly ornamentals. However, there is growing interest in the potential for using composts to prevent and control diseases in temperate agricultural and horticultural field crops and information concerning their use and effectiveness is slowly increasing. The impact of uncomposted plant residues, composts, manures, and compost extracts/teas on pests and diseases is discussed in relation to sustainable temperate field and protected cropping systems. The factors affecting efficacy of such organic amendments in prevent...
292 citations
TL;DR: Kudzu, Pueraria montana (Lour.) Merr. variety lobata (Willd) was introduced into the United States at the 1876 Centennial Exposition in Philadelphia, PA as discussed by the authors.
Abstract: Kudzu, Pueraria montana (Lour.) Merr. variety lobata (Willd.) was introduced into the United States at the 1876 Centennial Exposition in Philadelphia, PA. Subsequently, it was planted widely to reduce soil erosion by the Soil Erosion Service and Civilian Conservation Corp. Over 85 million seedlings of kudzu were provided to landowners by government agencies in the southeast in the first half of the 20th century. In 1953, kudzu was removed from the list of approved plants for erosion control, in 1970 it was officially labeled a weed, and in 1997 it was placed on the Federal Obnoxious Weed List. Its rapid elongation rates, high leaf area indices, high photosynthetic rates, and frequent rooting at stem nodes make kudzu an aggressive competitor with native shrubs and trees. Estimates are that kudzu currently covers 3 million hectares throughout the eastern United States and is spreading by 50,000 ha per year. Despite widespread anecdotal statements, little quantitative information is available regarding the e...
230 citations
TL;DR: Comparison studies currently underway on European native and American invasive genotypes of reed canary grass should shed light on the mechanisms responsible for reedCanary grass's aggressiveness and should provide an experimental protocol to test ecological and genetic hypotheses about what makes a species invasive.
Abstract: Invasive species pose a serious threat to native plant communities and are an important contributor to loss of biodiversity. In the case of Phalaris arundinacea, L. (Poaceae), reed canary grass, a cool-season, long-lived perennial plant native to Eurasia and North America, nonnative agronomically important genotypes were introduced to North America for numerous uses such as forage and soil stabilization. Following repeated introductions, reed canary grass became an aggressive invader that takes over natural wet prairies, stream-banks and wetlands. Reed canary grass can outcompete native plant species, resulting in monospecific stands with concomitant loss of plant and insect diversity and ultimately to alteration in ecosystem function. Abiotic factors such as disturbance, changes in hydrological regime, and particularly nutrient runoff to wetlands can enhance reed canary grass establishment and vegetative spread. In addition, the species' capacity for early season growth, rapid vegetative spread, high ste...
222 citations
TL;DR: This work focuses mainly on movement functions of the 30 K superfamily viruses, which encode MPs with structural homology to the 30 kDa MP of Tobacco mosaic virus, one of the most extensively studied plant viruses.
Abstract: Propagation of viral infection in host plants comprises two distinct and sequential stages: viral transport from the initially infected cell into adjacent neighboring cells, a process termed local or cell-to-cell movement, and a chain of events collectively referred to as systemic movement that consists of entry into the vascular tissue, systemic distribution with the phloem stream, and unloading of the virus into noninfected tissues. To achieve intercellular transport, viruses exploit plasmodesmata, complex cytoplasmic bridges interconnecting plant cells. Viral transport through plasmodesmata is aided by virus-encoded proteins, the movement proteins (MPs), which function by two distinct mechanisms: MPs either bind viral nucleic acids and mediate passage of the resulting movement complexes (M-complexes) between cells, or MPs become a part of pathogenic tubules that penetrate through host cell walls and serve as conduits for transport of viral particles. In the first mechanism, M-complexes pass into neighb...
220 citations
TL;DR: Cogongrass is a major impediment to reforestation efforts in southeast Asia, the number one weed in agronomic and vegetable production in many parts of Africa, and is responsible for thousands of hectares of lost native habitat in the southeastern U.S.
Abstract: Cogongrass is considered to be one of the ten most troublesome and problematic weedy species in the world. This species is found throughout tropical and subtropical regions, generally in areas dist...
TL;DR: Initial indications from deployment of transgenics with insect resistance in diverse cropping systems in USA, Canada, Argentina, China, India, Australia, and South Africa suggest that single transgene products in standard cultivar backgrounds are not a recipe for sustainable pest management, and a much more complex approach may be needed.
Abstract: Transgenic resistance to insects has been demonstrated in plants expressing insecticidal genes such as δ -endotoxins from Bacillus thuringiensis (Bt), protease inhibitors, enzymes, secondary plant metabolites, and plant lectins. While transgenic plants with introduced Bt genes have been deployed in several crops on a global scale, the alternative genes have received considerably less attention. The protease inhibitor and lectin genes largely affect insect growth and development and, in most instances, do not result in insect mortality. The effective concentrations of these proteins are much greater than the Bt toxin proteins. Therefore, the potential of some of the alternative genes can only be realized by deploying them in combination with conventional host plant resistance and Bt genes. Genes conferring resistance to insects can also be deployed as multilines or synthetic varieties. Initial indications from deployment of transgenics with insect resistance in diverse cropping systems in USA, Canada, Arge...
TL;DR: The basic ecology and life history of Japanese honeysuckle are well known and described here; however, research needs on the underlying causes of voracity and subsequent ecological impacts of this species are many as mentioned in this paper.
Abstract: Japanese honeysuckle (Lonicera japonica) was introduced outside of Asia in the early 19th century and is now invasive to varying degrees on every continent, except Anarctica, and many archipelagos. The basic ecology and life history of Japanese honeysuckle are well known and described here; however, research needs on the underlying causes of the voracity and subsequent ecological impacts of this species are many. Virtually all ecological experimentation with Japanese honeysuckle has been conducted in the southeastern U.S., thus more data are needed in other regions, particularly South America and Africa. Although Japanese honeysuckle is naturalized in many areas where it has been introduced, there still may be hope for the control of local infestations and its further spread in areas that have a fairly recent introduction history. Japanese honeysuckle may be secure throughout much of its introduced range, but land management principles that discourage its use and public education to prevent further dispersal are recommended strongly.
TL;DR: The emphasis of this review is on components of yield that can be modified either by selective breeding or through use of cultural techniques, and physiological components of seed yield, which are being increasingly exploited in new cultivar development.
Abstract: Squash and pumpkins are important horticultural crops worldwide, but there has been relatively little research to systematically describe yield components and improve productivity in this species. This review outlines some of the basic growth-analysis techniques for describing different aspects of productivity and attempts to summarize investigations on physiological, morphological, and ecological aspects of productivity and the relationship of these factors to eating quality in the three most important domesticated species of Cucurbita—C. pepo, C. maxima, and C. moschata. The emphasis of this review is on components of yield that can be modified either by selective breeding or through use of cultural techniques. Increasing economic crop yield while also balancing the needs to maintain and improve culinary qualities of the edible product will also be discussed. The bush phenotype is being increasingly exploited in new cultivar development. Advantages and disadvantages of using bush genotypes in cultivar d...
TL;DR: This article reviews the membrane interactions of a variety of peptides including alamethicin, melittin, cecropins, magainins, and defensins, finding that specific peptide–lipid interactions are particularly important in the case of antibiotic peptides.
Abstract: This article reviews the membrane interactions of a variety of peptides including alamethicin, melittin, cecropins, magainins, and defensins. The biological activities of the peptides are discussed and correlated to results from biophysical and structural studies. A picture emerges that allows one to understand the mechanisms of lysis and the regulation of the peptides' activities. Specific peptide–lipid interactions are particularly important in the case of antibiotic peptides, which affect the functionality of bacterial membranes, fungal membranes, or both but leave the bilayers of higher organisms, including those of the host cells, intact. Several models are presented and discussed in view of the ensemble of experimental data. These include the barrel stave, the wormhole, the carpet, and the detergent-like model.
TL;DR: A gene-based and a resource-based disease management approach should allow plant pathologists to incorporate the new science for fundamental research to solve practical problems of rice production.
Abstract: Rice production is subject to increasing environmental and social constraints. Agricultural labor and water, which are key resources for rice production, illustrate this point. Nearly all rice-producing countries face reduced availability of agricultural water and shortage of farm labor. Plant pathologists should be concerned with such large-scale evolutions because these global drivers have an impact on not only the rice production system but also on the individual field and single-rice-plant levels. These concerns are closely associated with the long-term sustainability and environmental consequences of the intensification of agricultural systems brought about by problems of feeding a rapidly growing human population. Furthermore, genetic diversity in rice production has been reduced, thus inducing frequent disease epidemics and pest outbreaks. Looking ahead, we need to realize the need to maintain the diversity and yet retain the high productivity of the system. Natural resources, including genetic res...
TL;DR: It is shown that very good evidence has been adduced for the presence and activity of pairing control genes in different allopolyploid species that are entirely bivalent forming and that display a strict disomic inheritance.
Abstract: Polyploidy has played a major role in the evolution of higher plants. Precise control of chromosome pairing is vital for conferring meiotic regularity, and hence reproductive stability in allopolyploids. In this review, we examine whether strong evidence has accumulated for the presence and activity of pairing control genes in different allopolyploid species that are entirely bivalent forming and that display a strict disomic inheritance. We show that very good evidence has been adduced in Triticum species, Avena sativa, Festuca arundinacea, Brassica napus, Gossypium hirsutum, and G. barbadense, and in amphidiploids related to the diploid species Lolium perenne, L. multiflorum, and L. rigidum. More circumstantial evidence has been obtained for polyploids in the genera Aegilops, Hordeum, Nicotiana, and Coffea, which have received far less attention than the other species. Although these pairing regulators seem to control different processes operating throughout the premeiotic interphase and the meiotic pro...
TL;DR: Uncharacterized aminotransferase-like sequences in the Arabidopsis genome are discussed in light of sequence motifs, publicly available transcript expression data, and sequence similarity to characterized homologs from other organisms.
Abstract: Aminotransferases are an important and diverse group of proteins. Of the approximately 25,000 predicted proteins in the Arabidopsis proteome, it is estimated that 4,000 are involved in cellular metabolism. Sequence analyses predict that roughly one percent of the “metabolism” sequences of Arabidopsis encode aminotransferases. Many plant aminotransferase genes have been identified, and their corresponding gene products have been localized and characterized. These studies have implicated aminotransferase reactions in a diverse variety of pathways in plants, including such primary metabolic pathways as amino acid biosynthesis and catabolism, photorespiration, and vitamin biosynthesis, as well as carbon and nitrogen shuttles, and plant stress responses. Thus, these enzymes may be reasonable targets for metabolic engineering to produce crop varieties with enhanced stress resistance and nutrient content. In addition, several aminotransferases that are absent from animals may be excellent targets for herbicides....
TL;DR: The elements of conformational coupling and molecular mechanisms of regulation of the two groups of protein kinases by Ca2+ and Ca2-/calmodulin in plants are summarized.
Abstract: Different input signals create their own characteristic Ca2+ fingerprints. These fingerprints are distinguished by frequency, amplitude, duration, and number of Ca2+ oscillations. Ca(2+)-binding proteins and protein kinases decode these complex Ca2+ fingerprints through conformational coupling and covalent modifications of proteins. This decoding of signals can lead to a physiological response with or without changes in gene expression. In plants, Ca(2+)-dependent protein kinases and Ca2+/calmodulin-dependent protein kinases are involved in decoding Ca2+ signals into phosphorylation signals. This review summarizes the elements of conformational coupling and molecular mechanisms of regulation of the two groups of protein kinases by Ca2+ and Ca2+/calmodulin in plants.
TL;DR: Recent advances in plant biotechnology may enable us to create sterile cultivars of these nonnative ornamental crops of commercial value that should reduce or eliminate the undesirable spread of some nonnative invasive plants into natural areas.
Abstract: The spread of invasive plants is one of the most challenging ecological problems in the 21st Century, causing a $35 billion loss per year to the economy in the United States alone. More than 50% of all invasive plants and 85% of invasive woody species were introduced originally for ornamental and landscape use. Because many nonnative plants are commercially important and widely utilized for various purposes, completely banning their use and prohibiting their imports are unpractical solutions for control. On the other hand, the methods currently used to control the spread of nonnative plants are ineffective, expensive, or environmentally problematic. Recent advances in plant biotechnology may enable us to create sterile cultivars of these nonnative ornamental crops of commercial value. The use of sterile cultivars should reduce or eliminate the undesirable spread of some nonnative invasive plants into natural areas.
TL;DR: This work reviews the literature on nontarget plants that can grow in pesticide-contaminated soil and water, and the fate of pesticides in filter strips, riparian buffers and vegetated remediation environments.
Abstract: Appropriate environmental management of pesticides includes their proper application, use of filter strips and riparian buffers to contain pesticides in runoff from fields, prompt cleanup of spills, and treatment processes for wastewater associated with manufacturing and equipment usage. Plants have beneficial effects in the management of pesticide-contaminated soil and water, including direct metabolism of many pesticides, stimulation of microbial activity in the root zone, extraction of contaminated water, and reduction of infiltrating contaminated water. In this work, we review the literature on nontarget plants that can grow in pesticide-contaminated soil and water, and the fate of pesticides in filter strips, riparian buffers, and vegetated remediation environments. Past research indicates that there are significant differences in the tolerance of plants to pesticides present in soil and water, and that some plants are more effective than others in the remediation of pesticide-contaminated soil and w...
TL;DR: It is believed that plant associations as well as the higher syntaxa can be regarded as fuzzy sets in an operational context for describing vegetation along ecological gradients in synthetic ways and can further the understanding of vegetation variation.
Abstract: The definition of vegetation types at different hierarchical levels, both to study the vegetation processes and for practical cartographic representation, is still considered a critical issue in many circles of plant ecologists. The problems are mainly related to the misleading idea that classification of the vegetation system, as developed by European phytosociologists during the last century within the discipline called syntaxonomy, would imply the assumption of the organismic concept of the plant community. After a short discussion on the role of Braun-Blanquet approach in plant ecology and in landscape ecology, the methods to detect multispecies responses along environmental gradients are briefly reviewed. In the main part of this article, we intend to stress that concepts considered critical, such as plant association and its ecological niche, are just operational tools that have nothing to do with the individualistic or organismic interpretation of plant communities in vegetation studies. Important ...
TL;DR: These findings strongly suggest that gymnosperm and angiosperm B genes have highly related interaction partners and equivalent functions in the male organs of their different host species.
Abstract: Class B floral homeotic genes play a key role in specifying the identity of male reproductive organs (stamens) and petals during the development of flowers. Recently, close relatives (orthologues) of these genes have been found in diverse gymnosperms, the sister group of the flowering plants (angiosperms). The fact that such genes have not been found so far, despite considerable efforts, in mosses, ferns or algae, has been taken as evidence to suggest that B genes originated 300–400 million years ago in a lineage that led to extant seed plants. Gymnosperms do not develop petals, and their male reproductive organs deviate considerably from angiosperm stamens. So what is the function of gymnosperm B genes? Recent experiments revealed that B genes from diverse extant gymnosperms are exclusively expressed in male reproductive organs (microsporophylls). At least for some of these genes it has been shown that they can partially substitute for the Arabidopsis B genes AP3 and PI in ectopic expression experiments,...
TL;DR: This review has focused this review specifically on plant topoisomerases, with an emphasis on their biological role in plant development.
Abstract: Regulation of the topological state of DNA is critical for cellular viability. DNA topoisomerases alter DNA topology and participate in nearly all events related to DNA metabolism such as replication, transcription, recombination, and chromosome segregation. Despite significant progress in our understanding of the structure, mechanism, and the role of topoisomerases in diverse cellular processes in bacteria, yeast, and animal systems, the roles of plant topoisomerases are poorly understood. In recent years expression studies, characterization of recombinant topoisomerases, and gene knockout studies have highlighted the importance of topoisomerases in plant DNA replication, mitosis, cell proliferation, organelle division, meiotic recombination, morphogenesis, and plant development. We have focused this review specifically on plant topoisomerases, with an emphasis on their biological role in plant development.
TL;DR: It is indicated that in vitro shoot organogenesis, just as in in vivo shoot development, is a complex, well-coordinated developmental process, and induction of a single molecular event may not be sufficient to induce the occurrence of the entire process.
Abstract: Shoot organogenesis is one of the in vitro plant regeneration pathways. It has been widely employed in plant biotechnology for in vitro micropropagation and genetic transformation, as well as in study of plant development. Morphological and physiological aspects of in vitro shoot organogenesis have already been extensively studied in plant tissue culture for more than 50 years. Within the last ten years, given the research progress in plant genetics and molecular biology, our understanding of in vivo plant shoot meristem development, plant cell cycle, and cytokinin signal transduction has advanced significantly. These research advances have provided useful molecular tools and resources for the recent studies on the genetic and molecular aspects of in vitro shoot organogenesis. A few key molecular markers, genes, and probable pathways have been identified from these studies that are shown to be critically involved in in vitro shoot organogenesis. Furthermore, these studies have also indicated that in vitro shoot organogenesis, just as in in vivo shoot development, is a complex, well-coordinated developmental process, and induction of a single molecular event may not be sufficient to induce the occurrence of the entire process. Further study is needed to identify the early molecular event(s) that triggers dedifferentiation of somatic cells and serves as the developmental switch for de novo shoot development.
TL;DR: The most recent data indicate an unconscionable 842 million people are chronically hungry in the world, 94 percent in developing countries as mentioned in this paper, and current food shortages, both chronic and acute, are concentrated in sub-Sahara Africa.
Abstract: The most recent data indicate an unconscionable 842 million people are chronically hungry in the world, 94 percent in developing countries. India, China, and other Asian countries that were the center of concern over hunger in 1960 have been among the most successful at increasing food production and consumption. Current food shortages, both chronic and acute, are concentrated in sub-Sahara Africa. There, production has lagged behind needs and fluctuations from natural and human-caused disasters have generated recurring food shortages and need for food aid. Three elements played critical roles in Asia and are likely to be the key to solving food shortages in Africa: rural/agricultural economic growth that generated increased incomes for the rural poor, stability of food prices, and non-agricultural economic growth. U.S. universities have educated many of the agricultural scientists in developing countries and those at CGIAR centers. The international agricultural programs of U.S. universities that have be...
TL;DR: The results of ongoing botanical research on taphonomic processes, genetic identification of ancient plant types, pollen analysis, phytoliths analysis, and seed identification directly affect the strength of paleoethnobotanical models of past human behavior.
Abstract: Paleoethnobotany is a growing subdiscipline of archaeology that utilizes information from numerous other disciplines to show the relationships between ancient plants and ancient peoples. The two primary disciplines that underlie paleoethnobotanical research are archaeology and botany. As such, the results of ongoing botanical research on taphonomic processes, genetic identification of ancient plant types, pollen analysis, phytoliths analysis, and seed identification directly affect the strength of paleoethnobotanical models of past human behavior. Preserved seeds form a significant portion of the archaeobotanical record. They represent not only the environment that was present when they were deposited but also a connection to the activity and culture of ancient people. Using the type of archaeobotanical remains and the archeological context of the remains, paleoethnobotanists study a diverse range of topics. These topics include, but are not limited to, the use of plants in ancient cultures, the developme...
TL;DR: It is proposed that more precise control of selection eases the practical application of resistance management strategies (high-dose–refugia) compared to other resistance strategies.
Abstract: The aim of resistance management is to slow and ideally reverse the development of resistance in the pest population. Since 1996, million of acres of crops have been planted that are genetically engineered with Bacillus thuringiensis (Bt) for insect resistance. The novelty for resistance management is that with Bt technology it is possible to control the principal force in an agroecosystem microevolutionary process from the outset, i.e., selection pressure. In Bt crops, the toxin can be expressed constitutively at a relatively constant dose or expression of the toxin can be restricted to specific crop stages, tissues, or both. Here we propose that more precise control of selection eases the practical application of resistance management strategies (high-dose–refugia) compared to other resistance strategies. The population genetics and ecological and operational factors related to the high-dose–refugia strategy currently used for Bt crops are also reviewed.