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Pennsylvania smartweed [Persicaria pensylvanica(L.) M. Gómez] is a common weed of rice (Oryza sativaL.) in the midsouthern United States and has recently become a concern for farmers because of reduced tillage systems. Acetolactate synthase (ALS) inhibitors have been extensively used for controlling smartweeds in imidazolinone-resistant and conventional rice. In the present study, we confirmed resistance to commonly used ALS inhibitors in rice and characterized the underlying resistance mechanism in aP. pensylvanicabiotype from southeast Missouri. A dose–response experiment was conducted in the greenhouse using bensulfuron-methyl, imazethapyr, and bispyribac-sodium to determine the resistance index (resistance/susceptibility [R/S]) based on GR50estimates. The target-siteALSgene was amplified from R and S plants, and sequences were analyzed for mutations known to confer ALS-inhibitor resistance. TheP. pensylvanicabiotype in question was found to be resistant to bensulfuron-methyl (R/S=2,330), imazethapyr (R/S=12), and bispyribac-sodium (R/S=6). Sequencing of theALSgene from R plants revealed two previously known mutations (Pro-197-Ser, Ala-122-Ser) conferring resistance to sulfonylureas and imidazolinones. This is the first report of ALS-inhibitor resistance inP. pensylvanica.

Broadleaf weed control on rice levees is an emerging problem faced by growers and consultants in Arkansas, USA. Field experiments were conducted at Lonoke and Stuttgart, Arkansas, in 2007 and 2008 to evaluate the effectiveness of various postemergence herbicides applied alone or in tank mixture with propanil or quinclorac for large-sized broadleaf weed control on rice levees. Rice injury was minimal (≤5%) from all herbicides at 2 weeks after treatment (WAT), and no injury was observed at 4 WAT. Sida spinosa (prickly sida) and Amaranthus palmeri (Palmer amaranth) were the most difficult-to-control weeds on levees. Of the herbicides applied alone, 2,4-D generally supplied the highest and most consistent weed control across the six species evaluated. Quinclorac was generally a better tank-mix partner than propanil for control of the weed spectrum evaluated. Propanil at 4.48 kg/ha lowered the activity of several systemic herbicides on S. spinosa, Polygonum pensylvanicum (Pennsylvania smartweed), and Ipomoea wrightii (palmleaf morningglory). Quinclorac plus 2,4-D was the most consistent tank mixture, providing more than 80% control of all weeds at 2 and 4 WAT, except A. palmeri.

Seed dispersal is an important process for plants, but may be particularly important for plants occurring in spatially isolated habitats like wetlands. Variation in the geographic distribution of wetland plant species may be strongly influenced by their ability to use waterbirds, particularly waterfowl to enhance dispersal. We used controlled feeding and germination experiments to investigate recovery, retention time, and germination for the seeds of 10 wetland plant species (Chenopodium album, Digitaria ischaemum, Echinochloa colonum, Echinochloa crusgalli, Eleocharis palustris, Panicum dichotomiflorum, Polygonum lapathifolium, Polygonum pensylvanicum, Rumex crispus, and Scheonoplectus maritimus) and compared how these metrics varied with seed characteristics. We fed a known number of seeds to captive raised mallards (Anas platyrhynchos) and collected fecal samples every 4 hours for 48 hours; all recovered seeds were planted in seedling trays and watched for 60 days to monitor germination. We co...

Current interest in biological-based management of weed seed banks in agriculture furthers the need to understand how microorganisms affect seed fate in soil. Many annual weeds produce seeds in high abundance; their dispersal presenting ready opportunity for interactions with soil-borne microorganisms. In this study, we investigated seeds of four common broadleaf weeds, velvetleaf (Abutilon theophrasti), woolly cupgrass (Eriochloa villosa), Pennsylvania smartweed (Polygonum pensylvanicum), and giant ragweed (Ambrosia trifida), for potential as sources of carbon nutrition for soil fungi. Seeds, as the major source of carbon in an agar matrix, were exposed to microbial populations derived from four different soils for 2 months. Most seeds were heavily colonized, and the predominant 18S rRNA gene sequences cloned from these assemblages were primarily affiliated with Ascomycota. Further, certain fungi corresponded to weed species, regardless of soil population. Relatives of Chaetomium globosum (98–99% sequence identity) and Cordyceps sinensis (99%) were found to be associated with seeds of woolly cupgrass and Pennsylvania smartweed, respectively. More diverse fungi were associated with velvetleaf seeds, which were highly susceptible to decay. The velvetleaf seed associations were dominated by relatives of Cephaliophora tropica (98–99%). In contrast to the other species, only few giant ragweed seeds were heavily colonized, but those that were colonized resulted in seed decay. The results showed that seeds could provide significant nutritional resources for saprophytic microbes, given the extant populations can overcome intrinsic seed defenses against microbial antagonism. Further, weed species-specific associations may occur with certain fungi, with nutritional benefits conferred to microorganisms that may not always result in seed biodeterioration.

Can banded herbicide be eliminated in ridge-tilled soybean (Glycine max)? The effects of banded herbicide, rotary hoeing and cultivation on weed populations and soybean yield in a ridge-tillage system were tested on three farms in Iowa, USA in 1989 and 1990. In 1989, plots either had no herbicide or had herbicide banded in the row at planting in mid-May; all plots received two rotary hoeings and two cultivations. In 1990, treatments were banded herbicide with no rotary hoeing, banded herbicide with one rotary hoeing, and no herbicide with one or two rotary hoeings; all plots received two or three cultivations. In both years, over all weed species [primarily giant foxtail (Setaria faberi), Pennsylvania smartweed (Polygonum pensylvanicum) and redroot pigweed (Amaranthus retroflexus)], seedling emergence was highest in late May and early June, with few seedlings emerging after mid-June. Weed populations were highest in May and June, after which rotary hoeing and cultivation reduced weed numbers in all plots. There were no consistent differences among treatments in weed numbers in early August for the 2 years. In both years, there was no significant difference in soybean yield among treatments. Within-farm mean yields ranged from 2.26 to 3.01 Mg ha−1among farms in 1989 and from 2.07 to 2.93 Mg ha−1among farms in 1990. Ridge-tillage without herbicide was generally equivalent to ridge-tillage with banded herbicide, with respect to total number of weeds and number of broad-leaved weeds remaining in August after tillage, and to soybean yield.

A laboratory bioassay was conducted to describe the effects of cold stratification and solid matrix priming (SMP®) on the germination response of common lambsquarters and Pennsylvania smartweed seeds. Treating seeds of common lambsquarters with a combination of cold stratification and SMP resulted in 78% germination compared with 13% in control seeds. Analogous treatments of Pennsylvania smartweed seeds resulted in 22% germination compared with 1% for control. Improved germination of common lambsquarters and Pennsylvania smartweed seeds suggested that the combination of cold stratification and SMP treatments have potential for improving seed germination in other weed species that exhibit high levels of seed dormancy. Nomenclature: Common lambsquarters, Chenopodium album L. #3 CHEAL; Pennsylvania smartweed, Polygonum pensylvanicum L. # POLPY. Additional index words: Seeds, scarification, stratification, sulfuric acid, potassium hydroxide. Abbreviations: H2SO4, sulfuric acid; KOH, potassium hydroxide; SMP, ...

Soil moisture is frequently manipulated by wetland managers to achieve a desired composition and production of plant species. Pink smartweed (Polygonum pensylvanicum) is a species valued by wetland managers because of its potential seed production and food base for migrating and wintering waterbirds. To improve ability to manage pink smartweed, we measured the influence of four growing-season soil moisture regimes (flooded, field capacity, prescribed moist-soil management, and continuously dry) in playa wetlands of the Southern High Plains of Texas. We used xylem water potential as an index of soil moisture available to the plants and compared vegetation and seed production among the four moisture treatments. Daily net photosynthesis was measured in each playa at 0900, 1200, and 1700 hours. The continuously-flooded wetland had the lowest absolute xylem water potential value (−0.294 MPa), followed by the playa at field capacity (−0.446 MPa), moist-soil managed playa (−0.758 MPa), and dry playa (−1.039 MPa). Vegetation biomass (F3,40 = 97.7, P < 0.001) and seed production (F3,40 = 54.3, P < 0.001) of pink smartweed differed among soil moisture treatments. Conducting moist-soil management (x = 6816 kg/ha) increased vegetation biomass by 44% over the dry treatment (x = 4706 kg/ha). As soil moisture increased to field capacity (x = 9010 kg/ha) vegetation increased by 32% above the moist-soil treatment. Maintaining standing water in a playa maximized vegetation production (x = 12497 kg/ha) of pink smartweed. Seed production was greatest when soil moisture was maintained at field capacity (x = 695 kg/ha). There was no difference in seed production between the moist-soil managed (x = 492 kg/ha) and flooded playas (x = 514 kg/ha), which was 28% lower than the field capacity treatment. Seed production in the dry treatment (x = 377 kg/ha) was 46% lower than the field capacity treatment and 25% below the flooded and moist-soil managed treatments. Net photosynthesis and xylem water potential decreased throughout the day in all treatments except continuously flooded, which corresponded to the increased vegetation production in this treatment. Slight increases in water stress relative to the continuously flooded treatment resulted in a redistribution of resources from vegetation to seed production. Managers should consider maintaining wetland soils at field capacity to increase seed production of pink smartweed.

Plants in playa wetlands are hypothesized to have high decomposition rates due to rapidly fluctuating water levels. Therefore, Polygonum pensylvanicum (a dominant playa species) decomposition rates were studied in relation to four water regimes (F1 (flooded 30% of 321 days), F2 (41%), F3 (58%), or F4 (100%)) in playa wetlands of the Southern Great Plains of Texas, 1996–1997. Decomposition rates of stems, leaves, and seeds were generally lowest (P

Field studies were conducted in 1998 and 1999 to evaluate crop response, weed control, Glycine max yield, and economic returns of labeled (1×) and one-half labeled (½×) rates of early preplant (EPP) sulfentrazone plus chlorimuron and postemergence glyphosate, compared to glyphosate-alone systems in no-till, narrow-row, glyphosate-resistant G. max. Treatments containing a 1× or ½× rate of EPP sulfentrazone plus chlorimuron with glyphosate followed by (fb) a postemergence treatment of glyphosate provided 80 to 100% control of Xanthium strumarium, Ambrosia artemisiifolia, and Polygonum pensylvanicum and 82 to 100% control of Setaria faberi and Amaranthus rudis if glyphosate was applied mid-postemergence (MPOST) or late postemergence (LPOST). Glyphosate alone EPP fb glyphosate postemergence or sequential postemergence treatments of glyphosate provided 77 to 100% control of S. faberi, A. artemisiifolia, and P. pensylvanicum. Glycine max yield did not significantly differ between treatments that contai...

Loss of wetlands to agriculture and development negatively impacts waterfowl. Greentree reservoirs are forested tracts that are purposefully flooded to increase hunting opportunities for sportsman and to provide shelter for waterfowl such as Mallards (Anas platyrhynchos). These human-made wetlands can also make natural foods such as acorns and invertebrates available to Mallards. Food habits analysis conducted in 1959 indicated acorns composed 24% of the volume of diets of Mallards collected from a variety of habitats including agricultural fields, naturally flooded bottomland forests, and greentree reservoirs in Arkansas. However, changes that may have occurred in food use by Mallards in bottomland hardwood habitats in Arkansas since last examined are unclear. We examined foods used by Mallards in greentree reservoirs from November 1990 to February 1991 in southeastern Arkansas. Seventeen species of plants and 21 families/orders of animals occurred in the diet of Mallards. Mallards consumed 65% plant matter, primarily seeds of narrowleaf foresteria (Foresteria angustifolia), Nuttall oak (Quercus nuttallii), Pennsylvania smartweed (Polygonum pensylvanicum), and rice (Oryza sativa). Invertebrate taxa, constituting 6% or more of the sample by both volume and mass, included the orders Coleoptera, Diptera, and Isopoda. Diets of Mallards present in greentree reservoirs in our study indicate Mallards still use natural foods, though agricultural seeds were in close proximity to natural foods.

Variation in the performance of 20 genotypes of Polygonurn pensylvanicum under two nutrient treatments was studied in a garden experiment. Nutrient fertilization enhanced vegetative biomass and fruit biomass production, but did not result in significant genotype-environment interactions, suggesting that nutrient variation of the range used in the experiment has little potential as a microevolutionary factor in this species. Leaf nitrogen concentration was not affected by a nutrient pulse. The degree of transient aphid infestation that occurred during the experiment had a weak positive correlation with final reproductive biomass of plants. Mean density of aphids per leaf was negatively correlated with percent leaf nitrogen and was not affected by genotypic identity of host plants. Resum6 : Dans un jardin experimental, les auteurs ont CtudiC la variation de performance de 20 genotypes du Polygonurn pensylvanicurn, en prCsence de deux rCgimes nutritionnels. L'apport en nutriments augmente la biomasse vCgCtative et la biomasse de la production en fruits, mais ne conduit pas i des interactions gtnoype-environnement significatives, ce qui suggkre que la variation en nutriments, aux quantitCs utilisCes pour l'expkrience, comporte peu de potentiel comme facteur microtvolutionnaire chez cette espkce. La teneur en azote foliaire n'est pas affectte par un apport ponctuel en nutriments. Le degrC d'infestation transitoire par les pucerons, observte au cours de I'exptrience, montre une faible corrtlation positive avec la biomasse reproductive finale des plants. La densitt moyenne des pucerons par feuille est en correlation inverse avec le pourcentage d'azote foliaire et n'est pas influencCe par I'identitC gCnotypique des plants h6tes. Mots clds : Pol~~gonumpensylvat~icut~~, gtnotype-environnement, interaction, plasticit6 phCnotypique, pucerons, nutriments. (Traduit par la rtdaction)

Investigation of the novel phenylpropanoid sucrose esters vanicoside A, vanicoside B and hydropiperoside, derived from Polygonum pensylvanicum L., by negative-ion fast atom bombardment and tandem mass spectrometry has elucidated collision-induced decomposition pathways and identified common trends of fragmentation for this class of compounds. The constant neutral loss spectrum of the crude extract of P. pensylvanicum, monitoring the loss of a p-coumaryl ketene fragment, can be used to identify homologues in the mixture for further investigation. This information can be used to characterize mixtures of this type of compound without the need for derivatization and prior to chromatographic separation, providing a method for guiding the isolation of similar compounds from crude extracts of other plants in the Polygonaceae family.

The Polygonum lapathifolium complex consists of populations that are widely distributed in the Northern Hemisphere and that have been classified at different taxonomic levels. Allozyme data were used to test the current North American taxonomic status of members of the complex (including P. lapathifolium var. lapathifolium, P. lapathifolium var. salicifolium, and P. scabrum) and to verify diploidy in the P. lapathifolium complex and polyploid origins of the morphologically similar P. persicaria and P. pensylvanicum. Of the 15 enzyme systems surveyed in 50 populations of the complex, only 3 of the 23 loci (Acon, Lap, and Skdh) were polymorphic in the North American populations and a total of 6 loci in European populations. Fifteen multilocus genotypes were evident in the complex. Four genotypes (all with Lap-10.67 were exclusive to North American populations of P. lapathifolium, providing support for a North American element of the complex. Nine genotypes (all with Lap-10.63) were found in North American and European populations of P. scabrum, all European populations of the P. lapathifolium complex, and three populations of North American P. lapathifolium var. lapathifolium. Lap-10.67 was also found in the native tetraploid P. pensylvanicum, whereas Lap-10.63 was found in the introduced tetraploid P. persicaria. Genetic distances among populations did not support the current taxonomic divisions within the complex, nor did it support separate species status of P. scabrum. Allozyme data provided support for the allotetraploid origins of P. pensylvanicum and P. persicaria, with members of the P. lapathifolium complex as one of the parents of each. Key words: Polygonum lapathifolium, Polygonum scabrum, Polygonum pensylvanicum, Polygonum persicaria, allozymes.

This experiment evaluated the efficacy of a new diamide insecticide, IKI-3106 50SL (cyclaniliprole), against MBB and JB. All insects were collected from wild populations at Kentland Research Farm in Blacksburg, VA, in the summer of 2014. MBB adults and larvae were collected from untreated snap bean plants, Phaseolus vulgaris , and JB adults were collected from untreated Pennsylvania smartweed, Polygonum pensylvanicum . All insects were brought back to the laboratory and maintained in cages for 24 h prior to use …

Suspected triazine resistant Pennsylvania smartweed plants were discovered near Holy Cross, Dubuque County, IA. Subsequent variable chlorophyllafluorescence assays confirmed these selections to be triazine resistant. This is the first reported evidence ofs-triazine resistance in Pennsylvania smartweed.

The isolation of the protein kinase C inhibitors, vanicoside A (1) and vanicoside B (2), from Polygonum pensylvanicum prompted continued interest in the active principles of this plant. A new, more efficient isolation procedure has been developed to facilitate separation of homologues of vanicosides A and B from the complex extract. Several new phenylpropanoid glycosides have since been isolated. The structures of these principles were determined to be 2'-O-acetylhydropiperoside (4), 6'-O-p-coumarylhydropiperoside (5), 4'-O-acetylvanicoside A (6), and 3'-O-acetylvanicoside B (7) using negative ion FABMS, 1 H NMR, and 2D NMR techniques.

Two new protein kinase C inhibitory glycosides, vanicosides A [1] and B [2] were isolated from Polygonum pensylvanicum (Polygonaceae) by chromatographic techniques guided by bioassays for PKC inhibition. The structures of these glycosides were established primarily by analysis of 1 H- and homonuclear correlated nmr and high-resolution fab mass spectra of 1 and 2 and the derived octaacetate, 3. Both glycosides were found to have p-coumaryl esters at the 1, 3, and 6 carbons of sucrose and a feruloyl ester at the 6' carbon. Vanicoside A [1] also had an acetate group at the 2' carbon

We determined true metabolizable energy (TME) and digestibility of 8 foods commonly available to Canada geese (Branta canadensis) in order to provide managers with a better understanding of the nutritional value of these foods. True metabolizable energy estimates were highest for chufa tubers (Cyperus esculentus ; 16.86 kJ/g), corn (Zea mays; 16.32 kJ/g), and milo (Sorghum vulgare; 15.72 kJ/g), while estimates for soybeans (Glycine max; 14.85 kJ/g), wild millet (Echinochloa crusgalli; 13.77 kJ/g), and rice (Oryza sativa; 11.76 kJ/g) were intermediate in value. Winter wheat foliage (Triticum aestivum; 10.04 kJ/g) and largeseed smartweed seeds (Polygonum pensylvanicum; 6.65 kJ/g) provided the least TME of foods tested. Crude fiber accounted for 76% of the variation in TME. Digestibility values of the 8 foods ranged from 35.1 to 88.5%, with digestibility varying widely among both agricultural and natural foods. To supply Canada geese with a balanced diet and foods high in metabolizable energy (ME), managers should provide a variety of agricultural and natural foods that are low in fiber content.

Brummitt & Taylor (1990) stated that they were "unable to see how or why" the epithet of Mammillaria esperanzaensis should be corrected (Heath 1989) to esperanzensis. They remarked that "it may be common practice to elide the final 'a' when forming such epithets", whereas elision is not involved. Steam (1983: 286) advised that "The first and each non-final component of a Latin compound consists of the stem of a word"; in the case of esperanzensis the stem is esperanz-, to which is added the Latin adjectival suffix -ensis ("indicates country or place of growth or origin or else habitat" Steam, 1983: 308). Recommendation 73D gives three examples of this process: "Ostrya virginiana (from Virginia), Eryngium amorginum (from Amorgos), Polygonum pensylvanicum (from Pennsylvania)". Amorgos is Greek, but in forming a Latin compound the -os case ending (the equivalent of the -us nominative singular case ending of many Latin Second or Fourth Declension nouns) is deleted before adding the Latin adjectival suffix -inum ("indicates possession or resemblance" Stearn, 1983: 309). The toponym Esperanza is a Spanish feminine noun meaning hope, and has an ending that is the exact equivalent of the case ending borne by Latin nouns of the First Declension, which end in -a in the nominative singular (except for some late borrowings from Greek, with -ri transliterated as -e). Steam (1983: 206) stated "Names of Latin form, whatever their origin, are treated grammatically as Latin words. Thus Africa, Alsatia, Jena, Japonia and others ending in -a are declined as feminine nouns in the First Declension". Steam gave the adjectival forms of those names as africanus, alsaticus, jenensis, and japonicus. Other well established examples are canadensis, cubensis andjamaicensis. Hence, as Esperanza ends in -a it is treated as a First Declension noun, and failure to delete the -a before adding a suffix is a correctable orthographic error. Even if, as Brummitt and Taylor argue, Article 73.1 does not itself require, but merely permits, the correction of orthographic errors, the correction of erroneously compounded adjectival epithets is nevertheless obligatory under Article 73.8, which is cited by Article 73.1 as an imposed standardization.

Polygonum pensylvanicum and Abutilon theophrasti, components of old—field communities in central Illinois were grown on a controlled soil moisture gradient to determine whether they exhibit different response centers. Germination response of a constant number of seeds per six moisture resource states, height, biomass, and reproductive response of initially constant numbers of plants per state were monitored. States, ranging from saturation down to 13.61 ± 5.53% moisture, are numbered in order of increasing drought. Maximum height of Polygonum occurred in states 4 and 5, and of Abutilon in 4, 5, 6. Vegetative and reproductive biomass maxima of Polygonum and Abutilon occurred in states 5 and 6, respectively. Abutilon reproduced only in states 5 and 6 where it overtopped the Polygonum canopy, while Polygonum reproduced in all states. Polygonum performance declined sharply in state 6. Thus, Polygonum and Abutilon response centers are displaced toward the wetter and drier ranges of the gradient, respectively. On a within—community level, Abutilon reproduces in less mesic resource states where Polygonum canopy height is reduced. In general, Abutilon reproduction may occur throughout the gradient when the Polygonum canopy opens. The performance of these species is strongly influenced by both physical and biotic conditions. Previously investigated adaptations, including drought resistance and rooting patterns in space and time, appear to underlie divergence along the moisture gradient. The response patterns found here are broad and exhibit considerable overlap as expected in fugitive strategies. The patterns of divergence shown on point and gradient scales in this and our previous work reflect a related complex of adaptations and strongly suggest that competitive divergence occurs in early successional communities.

Setaria faberii, Abutilon theophrasti, and Polygonum pensylvanicum growing together in a 1-yr successional field exhibit differing daily patterns of leaf water potential; S. faberii develops and maintains more negative water potentials than A. theophrasti, and P. pensylvanicum maintains much less negative water potential than either species. Setaria faberii and P. pensylvanicum do not light-saturate at 1.1 X 10 lx irradiance while A. theophrasti approaches light saturation at 8 x 10' lx, indicating that the species are adapted to high light intensities of the open field. In the field, leaf temperatures are maintained appreciably below air temperatures and are in the range of temperatures consistent with near-maximal photo- synthetic rates. Under optimal conditions the rates of photosynthesis are 38, 24, and 18 mg C02 * dm2 * h1 respectively for S. faberii, A. theophrasti, and P. pensylvanicum. Setaria faberii maintains near-maximum photosynthesis down to water potential of -12 bars, photosynthesizes at 30% of maximum at -24 bars, and recovers from potentials of -50 bars. In A. theophrasti photosynthesis remains unchanged to -10 bars, and becomes negligible at -26 bars. In P. pensylvanicum photosynthesis begins to decline sharply at potentials of -6 bars; it becomes negligible at -18 bars; and the plants die at -20 bars. The root systems of the three species grow in different parts of the soil resource: the root system of S. faberii is fibrous and shallow; the tap root of A. theophrasti is sparsely branched and extends to intermediate depths; the tap root system of P. pensylvanicum is moderately branched in the upper soil layers and pro- liferates mostly below the rooting zone of the other two species. The three species have evolved differing intercompenstory mechanisms for habitat ex- ploitation. One apparent niche difference among the species that allows for their coexistence is the exploitation of various levels of the soil and consequently different moisture resources.

Pennsylvania smartweed (Polygonum pensylvani- cum L.) achenes were harvested from plants growing either free from competition or in competition with corn (Zea mays L. 'Pioneer 3780') plants. Seeds were dormant when harvested. After 15 weeks of prechilling, 4 and 35% of the seeds germi- nated from plants with and without corn competition, re- spectively; after 30 weeks of prechilling, more than 92% of all seeds germinated. Scanning electron microscopy re- vealed that the carpel walls of achenes from plants with corn competition were porous with many channels. Carpel walls of achenes from plants without corn competition were without pores and channels. Transmission electron microscopy showed more lipid bodies in the embryo epidermal cells of seeds from plants with corn competition. Cell walls of em- bryos from non-prechilled seeds from plants with corn com- petition contained lipoidosomes that traversed cell walls. Lipoidosomes did not occur in cells of prechilled seeds. Additional index words. Zea mays, crop competition, electron microscopy, cell structure, germination.

Vegetative cover of weeds was determined in 84 agricultural fields representing a number of crops in Alaska. Multivariate statistical techniques were used with weed, soil, and management data to determine if weed vegetation was related to particular environmental and management variables. Field age was the variable that best explained the variation in vegetation composition. In fields recently cleared, native species were most important, being replaced by introduced weed species with increasing field age. Field horsetail (Equisetum arvenseL.) was an exceptional native species that persisted under cultivation. Total weed cover was low in the first few years of cultivation, but increased as introduced species such as common lambsquarters (Chenopodium albumL.), common chickweed [Stellaria media(L.) Cyrillo], quackgrass [Agropyron repens(L.) Beauv.], and foxtail barley (Hordeum jubatumL.) became more prevalent. A number of introduced species such as hempnettle (Galeopsis tetrahitL.) and Pennsylvania smartweed (Polygonum pensylvanicumL.) were restricted to just a few fields, emphasizing the importance of using weed-free seed and other management practices to minimize the spread of introduced weeds.

Weekly root extension of six successional annuals in glass-faced boxes was measured over a growing season in 42 soil resource states. Niche breadth and overlap were calculated and compared to values obtained from published root diagrams of eight tall grass prairie species. Differences in use of soil resources by the successional species were found and interpreted as primitive niche separation to avoid competition. Temporal displacement in absorption of moisture and nutrients is apparently important only to one species (Ipomoea hederacea). The six species showed marked differences in total composition of N, K, Ca, and Mg, although proportional similarities in nutrient use were high. The dominants of the successional community, Setaria faberii, Polygonum pensylvanicum and Ambrosia artemisiifolia had broader niches than the species with lower biomass and density. Two-dimensional overlap matrices in time and space showed Chenopodium album and Setaria to be highest in mean overall overlap, Polygonum and Ambrosia to be inter- mediate, and Abutilon theophrasti and Ipomoea to be lowest. The use of multidimensional resource states in the construction of an overlap matrix incorporating more than one parameter of the niche hypervolume was shown to be more useful than the multiplication of overlaps along each of the two parameters, space and time. Mean overlap in the use of underground space was considerably lower in the mature community (prairie) than in the successional community (oldfield). This corroborates the hypothesis that competition is less important in the evolution of fugitive species of the oldfield than of equilibrium species of the prairie.

The responses of Polygonum pensylvanicum L., an early successional annual, and of Polygonum virginianum L., a late successional perennial, were examined along discontinuous gradients of soil moisture, light and nutrient availability. In the case of P. virginianum both individuals grown from seed and individuals grown from rhizomes were examined. The results show that variation in the response of individuals of a species of different age to environmental variation is as great as that found between the two congeneric species of different successional habitats. In general, individuals of the two species were more similar to one another in response to the resource gradients when both were started from seed, than were individuals of P. virginianum grown from seed and from rhizomes. Potential differences in stored reserves (starting capital) between rhizomes and seeds appeared to have little effect upon responses to resource availability. A number of plant characters were found to vary along the gradients in ways that were unique to the character, the gradient, and the age of the individual. These characters included aspects of leaf size, shape, and orientation, as well as whole plant architecture. Many if not all of these characters are likely to have significant effects upon the functioning of plants. The origin of this difference in response to the gradients of individuals of P. virginianum of differing age may be ontogenetic or may reflect differences in genetic composition created by recombination.

Summary Freshly matured, seeds of the four summer annuals Ambrosia artemisiifolia, Polygonum pensylvanicum, Amaranthus hybridus and Chenopodium album were buried in soil at (12/12 h) daily thermoperiods of 15/6, 20/10, 25/15, 30/15 and 35/20°C and at a constant temperature of 5°C. After 0, 1, 3 and 5 months, seeds of each species at each temperature were exhumed and tested at a 14-h daily photoperiod at all six temperatures. Fresh seeds of A. artemisiifolia and P. pensylvanicum did not germinate at any temperature, those of A, hybridus germinated to 4 and 64% at 30/15 and 35/20°C, respectively, and those of C. album to 11–20% at 25/15, 30/15 and 35/20°C. Seeds of A. artemisiifolia and P. pensylvanicum, which germinate only in spring, required exposure to low (5, 15/6°C) temperature to after-ripen completely (i.e., to gain the ability to germinate over a wide range of temperatures), and little or no after-ripening occurred at high (25/15, 30/15 and 35/20°C) temperatures. Seeds of A. hybridus and C. album, which germinate in spring and summer, required exposure to low temperature to after-ripen completely, but at high temperatures they rapidly gained the ability to germinate at high temperatures. Regardless of the burial temperatures and species, when after-ripening occurred, seeds firs germinated at high and then at low temperatures. The minimum germination temperature for a species decreased with after-ripening temperature and with an increase in the length of the burial period.

To determine the roles of prior evolutionary divergence and competitive displacement of species in successional community organization, and aspects of the colonizing strategy, 6 co- occurring annuals were grown together and alone on a soil moisture gradient. The species had similar broad vegetative and reproductive responses to the gradient. Interspecific competition reduced the niche breadth and similarities of the species. Competitive and gradient stresses were generally ab- sorbed through plasticity, although Polygonum pensylvanicum and Chenopodium album showed some mortality. Response centers of Polygonum, Ambrosia artemisiifolia, and Chenopodium, com- petitively subordinate species, shifted due to interspecific competition. Amaranthus retroflexus and Setaria faberii, the leading competitors, already slightly offset from each other when grown alone, did not shift response centers. Competition delayed the start of flowering in Setaria, Chenopodium, Polvgonum and Ambrosia. Competitive success did not correlate with response breadth or overlap. Polygonum and Abutilon behaved differently in different competitive environments, indicating the existence of competitive refugia. Refugia may be shifted, reduced, or maintained depending on the competitors present. Coexistence may depend on: (1) differences in response to the moisture gradient and other niche dimensions previously investigated, and (2) on heterogeneous and unpredictable distributions of neighbors. Thus, competitive refugia will be unthreatened at some times and places. Key 'ords: colonizing strategy; community organization; competition; experimental gradient analysis; gradient: Illinois; niche; niche overlap; successional community.

The life history of Arhyssus lateralis (Say) was studied in Jackson County, Ill., May 1980–July 1982, and the immature stages were described. The bug was also reared from egg to adult in the laboratory. This bivoltine species overwinters as adults that become active in early to late May, begin feeding and copulating on the heads of maturing Rumex acetosella L., and lay eggs shortly thereafter; it occurs on this host into September. A. lateralis also feeds and reproduces on maturing R. crispus L. (June–August), Polygonum pensylvanicum L. (August–October), and P. hydropiperoides Michaux (August–October). Most eggs were laid singly on the four host plants and 1st–5th instars were never found off the hosts. Seasonal occurrence of the adults and subsequent immature stages is discussed. Adults were last observed during the third week of October. A. lateralis was reared on R. acetosella under a 16L:8D photoperiod at ca. 23.9°C. The incubation period averaged 9.19 days. The average durations of the five subsequent stadia were 4.98, 4.09, 4.08, 5.99, and 9.64 days, respectively.

A major obstacle limiting field studies in plant population biology is that there is no way of uniquely labeling or identifying the seeds produced by a mother plant so that her seedlings can be distinguished from the offspring of other conspecific plants. This article describes experiments undertaken to develop gamma—emitting radionuclide labels that are injected into a plant and are incorporated into the developing seeds and subsequent seedlings. The nuclides were used singly and in combination since each nuclide has unique spectral peaks that can be used to distinguish it from other nuclides. Five species were used: Phaseolus vulgaris, Polygonum pensylvanicum, Impatiens capensis, Bidens frondosa, and B. connata. Easily detectable levels of 58cobalt, 60cobalt, 134cesium, 137cesium, and 75selenium were incorporated by seeds of the five species. The incorporation of 54manganese and 65zinc varied among the species. 88Yttrium, 125antimony, and 85strontium were weak or not present as labels, depending on the species, while 110silver and 46scandium were never found in the seeds. Bean seedlings showed readily detectable amounts of nuclide label, while the nuclides apparently leached out of the Impatiens seedlings. The quantities of nuclides used in these experiments were so low that there was no effect of radiation on plant performance.

A model for determination of economic thresh- olds, or minimum weed population densities justifying the use of postemergence herbicide treatment, for five weed species in soybeans (Glycine max (L.) Merr.) is presented. Sensitivity analysis was performed on the model with respect to economic, statistical, and agronomic variables. The model was refined to include uncertainty about lost field days during the spraying period. Predictions from both the simple and refined models were consistent with economic theory. It was also determined that the economic threshold is sensi- tive to choice of data-collection ranges and functional form in weed-interference studies. Additional index words. Amaranthus bybridus L., Ambrosia artemisiifolia L., Ipomoea purpurea (L.) Roth., Polygonum pensylvanicum L., Xantbium pensylvanicum Wallr., inte- grated pest management, weather risk, AMBEL, PHBPU

The effects of Pennsylvania smartweed(Polygonum pensylvanicumL.) interference in soybeans [Glycine max(L.) Merr. ‘Pickett 71’] were studied in the field under a naturally occurring weed population. Soybean seed yield was reduced an average of 13% by a density of eight Pennsylvania smartweed plants per 10 m of row. Greater yield reductions of 21, 37, and 62% resulted from full-season interference by densities of 16, 32, and 240 weeds per 10 m of row, respectively. Fewer than five weeds per 10 m of row did not significantly reduce crop yield. A natural population of 240 weeds per 10 m of row did not reduce soybean yield if the period of interference was limited to 6 weeks or less after crop emergence. However, more than 6 weeks of weed interference resulted in significant yield reduction. Conversely, if the crop was kept weed-free for a period of 4 weeks or more after emergence, seed yield was not reduced. No allelopathic interaction between the two species was observed in greenhouse studies using a recirculating nutrient solution and alternate pots of soybeans and Pennsylvania smartweed.

The red-headed flea beetle, Systena frontalis (F.), was studied to assess its potential role as a pest of corn. The studies were centered in northwestern Iowa where the beetle had occurred in greatest density. In August 1968, 47 counties were surveyed to determine the density of flea beetles and their frequency of feeding on corn and weed hosts. The main host of the flea beetle was smartweed. Polygonum pensylvanicum L., but several other hosts were recorded for the first time. Eggs, collected from adults brought into the laboratory, required an exposure to cold before hatching occurred, but up to 70% hatched after various periods of exposure at 5. Only 1 adult was obtained from 1370 larvae placed on an artificial diet. The damage caused by the flea beetle is minor com pared with the rootworm infestations occurring in the area where red-headed flea beetles are most abundant in Iowa.

Seeds of yellow foxtail [Setaria lutescens(Weigel) Hubb.], ivyleaf morningglory [Ipomoea hederacea(L.) Jacq.], common cocklebur (Xanthium pensylvanicumWallr.), jimsonweed (Datura stramoniumL.), velvetleaf (Abutilon theophrastiMedic.), and giant ragweed (Ambrosia trifidaL.) were buried in the soil November 20 and 21, 1966 at Urbana, Illinois for noting emergence of seedlings from April 1 through August 18, 1967. Similarly, seeds of yellow foxtail, ivyleaf morningglory, jimsonweed, velvetleaf, giant ragweed, common ragweed (Ambrosia artemisiifoliaL.), and Pennsylvania smartweed (Polygonum pensylvanicumL.) were buried on October 25, 1968 for emergence observations from April 1 to August 18, 1969. Pennsylvania smartweed, giant ragweed, and common ragweed had large flushes of germination from early April through early May, with no emergence after June 1. Velvetleaf displayed similar early flushes and had additional small flushes of emergence in late May or June. Yellow foxtail seedlings also emerged in April and May in 1969 and in May and June during both years. Common cocklebur seedlings emerged abundantly in April and May but less abundantly in June. Ivyleaf morningglory and jimsonweed displayed flushes of emergence sporadically after May 1. Flushes of emergence for all species which occurred after May 1 were preceded by sufficient rainfall to bring the surface 10 cm of soil to field capacity. Cumulative heat units in the soil above 10 C were not correlated with initiation of emergence for any species. The early emergence was attributed to stimuli from general soil warming while emergence after May 1 was stimulated by favorable soil moisture from rainfall.

A study was made of the ontogeny of the achene of Polygonum pensylvanicum L. from fertilization to maturity. The proembryo is classified as the Polygonum Variation, Asterad Type. Cotyledons are initiated three days after anthesis, and by the fifth day procambium is present in the embryo axis. At approximately seven days after anthesis, the embryo begins to curve and occupy a marginal position in the ovary. By ten days the first foliage leaf primordium is initiated at the stem apex of the embryo. At maturity the embryo consists of two cotyledons, a plumule composed of the stem apex and one leaf primordium, and a hypocotyl with a well-developed radicle. Endosperm nuclei begin to divide before the first division of the zygote. Cell wall formation begins in the endosperm at the micropylar end of the embryo sac and proceeds toward the chalazal region. By the fifth day the endosperm is completely cellular, except for a basal projection; and a peripheral meristem has been established. At approximately ten days the peripheral meristem ceases periclinal cell division and becomes the aleurone. At the time of fertilization the ovary wall has its full complement of cell layers. The walls of the outermost cells elongate and become convoluted. Subsequent thickening and lignification of these cell walls produce the hard epicarp of the mature achene. ECONOMIC LOSSES caused by weeds have beein of importance since the beginning of plant cultivation. Among the features that account for the survival and competitive ability of weeds to thrive oni disturbed land are rapid growth, production of large numbers of seeds, prolonged seed dormancy, and sporadic germination. Polygonum pensylvanicum L. (Pennsylvania smartweed) possesses these characteristics. This annual weed grows along ditches, in damp grasslands, waste places, and cultivated ground. The reproductive or disseminating unit of this plant is an achene, often incorrectly referred to as a seed. Although numerous studies on the early stages of embryo development have been reported for members of the Polygonaceae (Soubges, 1919a, b, 1920a, b, 1924; Lonay, 1922; Mahony, 1936) as well as later stages (Stevens, 1912; Woodcock, 1914; Lonay, 1922), no developmental account has been found for the embryo of P. pensylvanicum. The food reserve within the mature achene of I Received for publication 27 January 1971. A portion of a thesis submitted in partial fulfillment of the requirement for the Ph.D. degree at Iowa State University, Ames. The author expresses his sincere gratitude to Dr. John E. Sass for invaluable guidance and criticism throughout this investigation. Thanks are extended to Dr. David W. Staniforth who provided plant material for this investigation. The research was supported in part under Project 1589 of the Agriculture and Home Economics Experiment Station, Iowa State University, David W. Staniforth, project leader; and by a National Science Foundation Summer Fellowship for Teaching Assistants, 1964. Journal Paper No. J-6819 of the Iowa Agriculture and Home Economics Experiment Station, Ames. the Polygonaceae has been reported either as perisperm (Harz, 1885; Coulter and Chamberlain, 1903; Eames, 1961) or endosperm (Lubbock, 1892; Dammer, 1893; Kraemer, 1910; Winton and Winton, 1932; Esau, 1965). Endosperm development in several members of this family has been described by Stevens (1912), Woodcock (1914), and Lonay (1922). The structure of the mature fruit wall in several genera has been described by Harz (1885) and Kraemer (1910). Sirrine (1895) described the cellular arrangement of the fruit wall in P. pensylvanicum and several other species of the Polygonaceae. Winton and Winton (1932) described and illustrated the mature pericarp of P. convolvulus L. and indicated that the fruit wall of P. pensylvanicum is similar. The only report on pericarp development in this genus is by Lonay (1922) in P. aviculare L. LaCroix (1961) used embryo culture, stratification, and electron microscopy techniques to study dormancy in both freshly harvested and stored achenes of P. pensylvanicum. The physiological condition of the embryo and features of enveloping structures can contribute to delayed germination. In freshly harvested achenes, dormancy seemed to be associated with the permeability of the fruit wall. The present study follows the ontogeny of the achene of P. pensylvanicum from fertilization to maturity. Special emphasis is placed on the rapidly developing embryo, endosperm, and maturing fruit wall. Knowledge of the development and the mature structure of the achene should aid future studies on the permeability of

Six populations of the annual plant Polygonum pensylvanicum were analysed for isozyme variability and reproductive effort. The populations were found to be similar in both their isozyme constituents and in their mean reproductive efforts. Mean reproductive effort did not correlate with mean population heterozygosity nor did individual reproductive effort correlate with individual heterozygosity. Polygonum pensylvanicum exhibits several of the features which have been predicted for weedy plant species.

Rates of photosynthesis were measured in each of six replicated genotypes for each of two Polygonum species at five light and seven temperature levels. The early successional species, Polygonum pensylvanicum L., exhibited higher rates of photosynthesis and a more sun-tolerant behavior compared to its later successional relative, Polygonum virginianum L., results that are consistent with previously observed successional trends. Quantitative comparisons of individual genotype plasticity and between-genotype variation indicate that, in general, plasticity contributes more to population flexibility in photosynthetic response of these species than does between-genotype variation. However, the relative contribution of between-genotype variation was found to vary depending on the environmental variable and species studied. Between-genotype variation assumed greater importance in the temperature response than in the light response. Similarly between-genotype variation was more important in P. virginianum than in P. pensylvanicum supporting the notion that later successional species are less plastic. These results establish that significant levels of photosynthetic variation occur even within populations.

The behavior of Polygonum pensylvanicum L., an early successional annual, and Polygonum virginianum L., a later successional perennial were compared on singlefactor gradients of light, nutrients and soil moisture and on a double-factor gradient of light and nutrients. The two species were grown together as well as alone. In most cases, the early successional species was more productive and allocated less of its biomass to belowground parts relative to its later successional congener. The early successional species was also more opportunistic in its utilization of resources as evidenced by its greater responsiveness to varying resource availability. The role of perenniality in the later successional species may be dual. Individuals of P. virginianum started from seed were more responsive to deficiencies in resources than were individuals started from rootstocks in these experiments. In the single-factor experiments where plants were started from seed, there were numerous significant interactions between levels of light, nutrients or moisture with competition in both species. In the double-factor experiment, however, there were no statistically significant interactions between light, nutrients and competition in the perennial started from rootstocks, but all possible interactions were significant in the early successional annual. The result of a large, underground reserve in the perennial was that the effects of resource availabilities of light and nutrients were uncoupled. The competitive superiority of the early successional species over the later successional species was greatly diminished when the later successional species was started from rootstocks instead of from seeds. Regardless of whether individuals of P. virginianum were started from seed or from rootstocks the results of competition between the two species indicate that the early successional species is competitively more competent when resources are abundant and that the later successional species is competitively more competent when resources are scarce.

Polygonum pensylvanicum, spec. nov. 14. Polygonum floribus octandris digynis, pedunculis hispidis, foliis lanceolatis. Habitat in Pensylvania . Kalm. Facies & habitus Polygoni 11, sed majora strictiora omnia. Caulis ramosus, angulatus. Folia lanceolata, acuminata, subtus admodum scabra. Stipulae truncatae, muticae. Pedunculi scabri, setis rigidiusculis apice gluten secernentibus. Spicae subracemosae, flosculis pedicellatis. * Polygonum foliis indivisis, floribus octandris., Published as part of Linnaeus, Carolus, 1753, Species plantarum: exhibentes plantas rite cognitas, ad genera relatas, cum differentiis specificis, nominibus trivialibus, synonymis selectis, locis natalibus, secundum systema sexuale digestas, Stockholm :Laurentius Salvius on page 362, DOI: 10.5281/zenodo.3931989

SUMMARY (1) An abundant mycoflora was found on the seed of Abutilon theophrasti, Datura stramonium, Ipomoea hederacea, and Polygonum pensylvanicum, which are colonizing annuals of early successional habitats. The fungal species differed among the plant species and most were specialists with respect to their hosts. (2) A more extensive mycoflora occurred within seed of Polygonum pensylvanicum and D. stramonium than within seed of I. hederacea and A. theophrasti. Ipomoea hederacea and A. theophrasti had greater resistance to fungal infection than P. pensylvanicum and D. stramonium. Fungi differed in their ability to penetrate seeds. (3) Seed germination and seedling development were affected, both quantitatively and qualitatively, by the fungal isolates. Polygonum pensylvanicum seedlings were more susceptible to fungal invasion than those of A. theophrasti or I. hederacea. (4) Extracts from all tissues of I. hederacea and from the roots of A. theophrasti had antifungal activity. Little activity was detected in extracts from P. pensylvanicum. (5) Plant densities of I. hederacea, D. stramonium and P. pensylvanicum remained fairly constant in the field, after seedling emergence, irrespective of density or species diversity. (6) Fungi mainly affected seed germination and the development of young seedlings; at later stages, herbivory became more important in plant survival.