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Aim How plants cope with increases in population density via root plasticity is not well documented, although abiotic environments and plant ontogeny may have important roles in determining root response to density. To investigate how plant root plasticity in response to density varies with soil conditions and growth stages, we conducted a field experiment with an annual herbaceous species (Abutilon theophrasti). Methods Plants were grown at low, medium, and high densities (13.4, 36.0, and 121.0 plants m−2, respectively), under fertile and infertile soil conditions, and a series of root traits were measured after 30, 50, and 70 days. Results Root allocation increased, decreased, or canalized in response to density, depending on soil conditions and stages of plant growth, indicating the complex effects of population density, including both competitive and facilitative effects. Main conclusions Root allocation was promoted by neighbor roots at early stages and in abundant resource availability, due to low‐to‐moderate belowground interactions among smaller plants, leading to facilitation. As plants grew, competition intensified and infertile soil aggravated belowground competition, leading to decreased root allocation in response to density. Root growth may be more likely restricted horizontally rather than vertically by the presence of neighbor, suggesting a spatial orientation effect in their responses to density. We emphasized the importance of considering effects of abiotic conditions and plant growth stages in elucidating the complexity of density effects on root traits., The research revealed the complexity of root response to density, which may increase, decrease, or canalize, depending on the strength of above‐ and belowground interactions, which varied with soil conditions or growth stage.

BACKGROUND Herbicides acting on biosynthesis of plant pigments have contributed greatly to weed control in recent years. In our previous studies, 2-methoxybenzamides were discovered as a novel type of lead compound for the development of bleaching herbicides. RESULTS A total of 67 benzamide analogues were synthesized and evaluated for herbicidal activity. The structure-activity relationship (SAR) revealed that a methoxyl substitution at the 2-position of the benzoyl moiety is essential for the herbicidal activity of benzamide derivatives, and introduction of small substituents at the meta- or para-position of the benzylamine moiety is also beneficial. Compounds 4, 43 and 44 showed 100% inhibition against Abutilon theophrasti and Amaranthus retroflexus at an application rate of 150 g a.i. ha-1 . CONCLUSION The relationship between the structure and herbicidal activity of 2-methoxybenzamides was discussed intensively. Compounds 4, 43 and 44 may serve as novel candidates with a bleaching effect. © 2021 Society of Chemical Industry.

Agronomy Journa l • Volume 108 , I s sue 3 • 2016 Waterhemp is a diffi cult-to-control weed in maize, soybean [Glycine max (L.) Merr], and grain sorghum [Sorghum bicolor (L.) Moench] production, due to its competitive ability, outcrossing nature, high degree of genetic diversity, and resistance to multiple herbicide sites-ofaction (Horak and Loughlin, 2000; Hager et al., 2002; Steckel and Sprague, 2004; Steckel, 2007; Heap, 2015). Atrazine is still commonly used in maize and grain sorghum for PRE or POST control of waterhemp (Anderson et al., 1996) and other annual dicot weeds, in spite of hundreds of cases of triazine resistance occurring within Amaranthus spp. worldwide (Heap, 2014, 2015). Previous research reported that elevated rates of atrazine metabolism via GST activity contribute to atrazine POST resistance within two waterhemp populations (Ma et al., 2013). Th e MCR and ACR are both resistant to atrazine POST, and their responses have been compared with an herbicide-sensitive population, WCS (from Wayne County, Illinois) (Patzoldt et al., 2005; Hausman et al., 2011; Ma et al., 2013). Diff erences in PRE vs. POST activity of atrazine among several atrazine-resistant waterhemp populations identifi ed from Illinois were noted in previous studies (Patzoldt et al., 2003, 2005). In particular, an atrazine-resistant waterhemp population from Illinois (diff erent than MCR and ACR) was not resistant to atrazine PRE at a rate of 1.5 kg ha–1 (Patzoldt et al., 2003). Moreover, the ACR and MCR populations were not controlled but responded equally to atrazine POST at the rate of 560 g ha–1 (Hausman et al., 2011), and both populations demonstrated almost identical rates of atrazine metabolism (Ma et al., 2013) when 14C-atrazine was supplied using an excised-leaf assay (Ma et al., 2015). In addition to waterhemp, other dicot weed populations (most notably Abutilon theophrasti Medic.) have displayed non target-site resistance (NTSR) to atrazine POST (Anderson and Gronwald, 1987; Gronwald et al., 1989; Gray et al., 1996), and each has displayed enhanced rates of rapid metabolism via glutathione-atrazine conjugation (catalyzed by elevated GST activity) as the mechanism of resistance (Anderson and Gronwald, 1991; Gray et al., 1996). Th is is an important physiological factor to consider when studying NTSR mechanisms in weeds because GST enzymes are encoded by nuclear genes (Anderson and Gronwald, 1987; Patzoldt et al., 2003; Frova, 2006). In contrast, the target site for atrazine Differential Responses to Preemergence and Postemergence Atrazine in Two Atrazine-Resistant Waterhemp Populations

Several different alkoxycarbonyl-substituted 2-benzoxazolinone moieties have been incorporated into a tetrahydroisoindoline-1,3-dione scaffold to provide 25 compounds (1a–1u and 2a–2d). The structures of these compounds were confirmed by 1H and 13C NMR, HRMS and X-ray single-crystal diffraction. Some of these compounds (1g, 1h, 1j, 1k) exhibited excellent herbicidal activities against Abutilon theophrasti, Amaranthus retroflexus and Echinochloa crus-galli at a rate of 375 g AI·ha−1. Among them, compounds 1h and 1j displayed the best post-emergence herbicidal effect against Abutilon theophrasti with ED50 values of 1.8 and 5.3 g AI·ha−1, respectively, which are superior to that of the commercial acifluorfen (44.3 g AI·ha−1). Field trials demonstrated that compound 1h exhibited similar herbicidal activity to a high concentration atrazine, and found to be safer for maize than atrazine. The results of this study therefore show that compound 1h could potentially be used as a post-emergence herbicide for maize fields.

Summary Weed seeds in and on the soil are the primary cause of weed infestations in arable fields. Previous studies have documented reductions in weed seedbanks due to cropping system diversification through extended rotation sequences, but the impacts of different rotation systems on additions to and losses from weed seedbanks remain poorly understood. We conducted an experiment in Iowa, USA, to determine the fates of Setaria faberi and Abutilon theophrasti seeds in 2-, 3- and 4-year crop rotation systems when seed additions to the soil seedbank were restricted to a single pulse at the initiation of the study. Over the course of the experiment, seedlings were removed as they emerged and prevented from producing new seeds. After 41 months, seed population densities dropped >85% for S. faberi and >65% for A. theophrasti, but differences between rotation systems in the magnitude of seedbank reductions were not detected. Most of the reductions in seedbank densities took place from autumn through early spring in the first 5 months following seed deposition, before seedling emergence occurred, suggesting that seed predation and/or seed decay was important. For S. faberi, total cumulative seedling emergence and total seed mortality did not differ between rotation systems. In contrast, for A. theophrasti, seedling emergence was 71% lower and seed mortality was 83% greater in the 3- and 4-year rotation systems than in the 2-year system. Results of this study indicate that for certain weed species, such as A. theophrasti, crop rotation systems can strongly affect life-history processes associated with soil seedbanks.

BACKGROUND Root-knot nematodes and soil-borne diseases constrain the rapid development of protected agriculture in China, especially while phasing out methyl bromide (MB). The fumigant sulfuryl fluoride (SF) is currently used as an alternative to MB for the disinfestation of buildings and post-harvest commodities. Our experiments aimed to evaluate a novel application of SF as a soil fumigant in greenhouses in China. RESULTS Dose–response experiments indicated that SF has good efficacy on root-knot nematodes (Meloidogyne spp.) and moderate activity against Fusarium spp. and weeds (Digitaria sanguinalis (L.) Scop. and Abutilon theophrasti Medicus). The field trials indicates that SF has good efficacy, between 80 and 94%, on Meloidogyne spp., and Fusarium spp. at the rates of 25–50 g m−2 in tomato and cucumber in Beijing and Shandong Province. Marketable yield and plant vigour was not significantly different in SF and MB treatments. SF has lower emissions than MB during the fumigation operation. It is simple to apply, can be used at low temperature, and has a short plant-back time. SF was found to be an economically feasible alternative to MB for nematode control in China. CONCLUSION SF can be used as a soil fumigant to control root-knot nematodes and to reduce the levels of key soil pathogens. © 2013 Society of Chemical Industry

Summary Soyabean (Glycine max) was grown at ambient and projected levels of atmospheric carbon dioxide (+250 μmol mol−1 above ambient) over two field seasons with and without the presence of a weed, Abutilon theophrasti, to quantify the potential effect of rising atmospheric carbon dioxide concentration on weed–crop interactions and potential yield loss in soyabean. Under weed-free conditions, elevated CO2 resulted in stimulations in soyabean seed yield and associated components, including pod number. At an approximate density of 6 plants m−2, A. theophrasti competition resulted in a significant reduction (−40%) in soyabean seed yield. Although differences in seed yield reduction by A. theophrasti were observed as a function of year, the relative decrease in seed yield with A. theophrasti biomass did not differ in response to CO2. Although careful weed management will be necessary if CO2-induced increases in seed yield for soyabean are to be achieved, these data suggest that soyabean seed yield may be more resilient in competition with A. theophrasti as a function of rising atmospheric levels of carbon dioxide.

Thirteen novel N-(2-fluoro-5-(3-methyl-2,6-dioxo-4-(trifluoromethyl)-2,3-dihydropyrimidin-1(6H)-yl)phenyl)-2-phenoxy)acetamides were designed and synthesized utilizing 4-fluoro-aniline and ethyl 3-amino-4,4,4-trifluoro-but-2-enoate as starting materials. The chemical structures of all compounds were confirmed by 1H NMR, IR, mass spectrum and elemental analyses. Subsequently, the herbicidal activities of the as-prepared compounds were evaluated in the greenhouse. Bioassay results indicated that most of compounds had better herbicidal activities against dicotyledonous weeds. Among all the tested compounds, compounds 4a–4i showed good herbicidal activities at both pre-emergence and post-emergence treatment against two or three kinds of dicotyledonous weeds, such as Abutilon theophrasti Medic, Amaranthus ascendens L, and Chenopodium album L at the dosage of 75 g ai/ha.

Abutilon pitcairnense Fosberg (Malvaceae) is currently extinct in the wild. It is endemic to Pitcairn Island, in the South Central Pacific. Islander Carol Warren refound it in 2002, after a period of over 20 years, during which time it was presumed extinct. The history of its collection and naming, its taxonomy, a botanical description and the first botanical illustrations of Abutilon pitcairnense are provided from plants flowering at the National Botanic Gardens of Ireland, Glasnevin, Dublin in January 2010, the former and current location on Pitcairn Island, former habitat photograph, and cultivation requirements are discussed.

Pakisides A and B (1 and 2, resp.), new catalpol-type iridoid glycosides, and a new glycoside, 3, of scutellarein have been isolated from the AcOEt-soluble fraction of the whole plant of Abutilon pakistanicum, along with buddlejoside and lapachol. The structures of new compounds were elucidated by spectroscopic techniques including 1H-and 13C-NMR (DEPT), and 2D-NMR experiments.

During the last ice age, CO2 concentration ([CO2]) was 180-200 micromol/mol compared with the modern value of 380 micromol/mol, and global temperatures were approximately 8 degrees C cooler. Relatively little is known about the responses of C3 and C4 species to long-term exposure to glacial conditions. Here Abutilon theophrasti Medik. (C3) and Amaranthus retroflexus L. (C4) were grown at 200 micromol/mol CO2 with current (30/24 degrees C) and glacial (22/16 degrees C) temperatures for 22 d. Overall, the C4 species exhibited a large growth advantage over the C3 species at low [CO2]. However, this advantage was reduced at low temperature, where the C4 species produced 5 x the total mass of the C3 species versus 14 x at the high temperature. This difference was due to a reduction in C4 growth at low temperature, since the C3 species exhibited similar growth between temperatures. Physiological differences between temperatures were not detected for either species, although photorespiration/net photosynthesis was reduced in the C3 species grown at low temperature, suggesting evidence of improved carbon balance at this treatment. This system suggests that C4 species had a growth advantage over C3 species during low [CO2] of the last ice age, although concurrent reductions in temperatures may have reduced this advantage.

Weed tolerance of UV-B radiation varies with species, and the radiation could affect weed ecology and management. Variations in growth, photosynthesis and defense system among four important agronomic weeds, Abutilon theophrasti Medik, Amaranthus retroflexus L., Digitaria sanguinalis (L.) Scop and Chloris virgata Swartz, under increased UV-B radiation (ambient and increased radiation at 2.7, 5.4 and 10.8 kJ-m−2-d−1) were studied in the greenhouse experiment. After 2 weeks of radiation, the shoots’dry mass decreased with increasing UV-B radiation except for D. sanguinalis. The reduction in biomass was the result of changes in morphology and physiology. Higher levels of UV-B treatment decreased the leaf area, plant height, net photosynthetic rate and chlorophyll contents, while it increased the contents of wax and UV-B absorbing compound in all species, except for A. retroflexus, which did not increase significantly. The activity of superoxide dismutase, catalase, ascorbate peroxide and the content of ascorbic acid changed differently among the weed species as UV-B radiation increased. D. sanguinalis was the most tolerant and A. retroflexus the most sensitive to increased UV-B radiation. The results also show that the two grass species (D. sanguinalis and C. virgata) were more tolerant to UV-B radiation than the two broad-leafed species (A. theophrasti and A. retroflexus). The UV-B absorbing compound and leaf wax played important roles against UV-B damages in the two grass weeds. The overall results suggest that weed community, competition and management will be altered by continuous ozone depletion. (Handling editor: Li-Xin Zhang)

Twelve isolates of Diaporthe/Phomopsis species from soybean (six isolates) and Abutilon theophrasti (velvetleaf) (six isolates) were studied for their pathogenicity to soybean and their effect on soybean seed germination and seedling survival after artificial seed inoculation. The following criteria were taken into consideration: number of germinated and rotten seeds, seedlings with necrosis, germ length and length of necrotic lesion. All tested Diaporthe/Phomopsis isolates caused seeds rot. P. longicolla isolates from soybean plants (PL1 and PL2) and isolates from velvetleaf (AbPL1 and AbPL2) exhibited statistically significant decrease in germ growth. These germs were only 1.0–1.8 cm long. No relation between length of germs and length of necrosis was found. The highest percentage of decayed seedlings was determined in the isolates AbPL1 and 2 as well as in PS 1 and PL 1 20 days after inoculation. Results of our research showed that Diaporthe/Phomopsis species from velvetleaf could be more pathogenic on soybean than isolates of the same species from soybean.

Summary 1. We examined biomass and root proliferation responses of Abutilon theophrasti Medic. to the density of high nutrient patches and the patch‐background contrast. Contrast in nutrient content between a patch and the background soil, as well as patch density, are important features of heterogeneous soil environments that have received little research attention. 2. Plants were grown in pots with no, one or two organic nutrient patches, and the equivalent nutrition of no, one or two patches in the background soil in a factorial design. Plant performance (root and shoot biomass) and root proliferation (root length inside and outside high-nutrient patches) were measured. 3. Root and shoot biomass increased with increasing nutrient heterogeneity, and root biomass declined with increased background soil nutrient availability. Patch‐ background contrast did not alter root or shoot biomass, nor allocation to roots. Biomass responses appeared to be driven by heterogeneity, as plants with access to the same total nutrients were larger when nutrients were concentrated in patches. The root proliferation response was not affected by either the density of patches or the degree of contrast. 4. A conceptual model is presented describing how a plant’s overall nutrient status could respond to changes in the patch‐background contrast. The model predicts that nutrient-sufficient plants should not respond to patches, but nutrient-limited plants should proliferate roots proportionally to the contrast. The proliferation response should saturate when the total nutrients in both patch and background are no longer limiting.

The Tanzanian medicinal plant Abutilon grandiflorum G. Don was studied for its in vivo and in vitro antiplasmodial effects. The ethyl acetate extract showed prominent in vivo activity against P. vinckei vinckei in mice and in vitro against P. falciparum strains HB3 and FCB. The extract was only moderately cytotoxic if tested in vitro against the colon cell line HT29. In the in vivo study, the results were significantly influenced by the treatment schedule used, i.e. early treatment with higher doses was more successful than applying the same overall amount over a longer period. Phytochemical analysis of the extract provided no conclusive evidence for the observed parasitological effects.

Weed competition studies with grain sorghum [Sorghum bicolor (L.) Moench are limited. Improved knowledge of growth in response to weed competition could contribute to development of sorghum hybrids that compete better with weeds. Velvetleaf (Abutilon theophrasti Medic.) competition with sorghum hybrids was evaluated in field experiments on a Sharpsburg silty clay loam soil (fine smectitic, mesic Typic Arguidoll) in 1996 and 1997 at Lincoln, NE. The objective was to determine the effects of velvetleaf competition on interception of photosynthetically active radiation (PAR), growth, and yield of sorghum hybrids with different heights. Sorghum hybrids used were 'FS2' (1.8 to 2.4 m tall) and 'DK54' and 'X260' (1.2 to 1.5 m tall). Weed treatments included sorghum in monoculture and grown in mixture with velvetleaf. Medium-height hybrids had 0.4 greater mid-season leaf area indices (LAIs) than the tall hybrid in 1996, and in 1997, DK54 had 0.4 to 0.6 greater LAI than the other hybrids after 500 growing degree days. Interception of PAR was similar among hybrids except for 2 to 10% less for X260 in mixture in 1996. In 1996, when weed pressure was greater, the tall hybrid had greater relative growth rate and net assimilation rate but lower leaf area ratio than for the medium-height hybrids. Sorghum intercepted more radiation and produced more biomass in monoculture than in mixture, but the reduction in growth and yield in presence of velvetleaf was less for the tall hybrid. Development of tall sorghum hybrids with high LAI would be useful for integrated weed management.

Velvetleaf seeds have been found in imported grains in Japan. The plants from these seeds show a weedy growth habit, such as that seen in the noxious velvetleaf which has recently emerged in Japan and noted in our previous study. To elucidate the genetic background of the velvetleaf strains found in imported grains we evaluated the genetic variation of six strains and an additional 39 worldwide velvetleaf accessions using the intersimple sequence repeat (ISSR) polymorphism. Cluster analysis based on the ISSR polymorphism emitted two major clusters which corresponded well with classification by growth habit, that is, crop type and weed type. Five of the six strains from the imported grains formed a small cluster. All six strains united into one major cluster containing the weed type accessions, while all of the old Japanese accessions formed another major cluster containing the crop type accessions. The genetic difference between imported weedy velvetleaf and old Japanese accessions suggests that imported velvetleaves are the source of the recent outbreak of the noxious velvetleaf in Japan.

The source of the velvetleaf spreading its distribution rapidly and causing serious problems in forage fields all over Japan since the mid 1980s was thought to be a new accidental introduction of seeds from velvetleaf mingled in some imported grains from the USA and Australia. However, velvetleaf used to be cultivated as a fiber crop until the 1880s. We examined the intraspecies variations, such as morphological characteristics and growth habits, using accessions previously collected and obtained from imported grains. Using principal component analysis (PCA), the accessions were classified into crop type and weed type. The crop type capsule was mostly an ivory color, and the weed type was mostly an ebony color. The crop type showed characteristics of a fiber crop, such as an erect form, uniform flowering and a low seed dormancy rate. Conversely, the imported grains were classified into the weed type which showed a strong weedy nature, such as branched form, long flowering period, high reproductive ability and a high dormancy rate. These results suggest that the new introduction is different from the indigenous fiber crop, and may possibly be the source of the present invasive velvetleaf because of its strong weedy nature. However, further studies comparing the new introduction directly with the present velvetleaf are necessary.

Selection of crop genotypes that are more competitive with weeds for light interception may improve crop yield stability in the presence of weeds. The effects of interference on ecophysiological characteristics of Abutilon theophrasti Medic. and three morphologically diverse grain sorghum hybrids was evaluated to determine the relative tolerance and suppressive ability of the three hybrids and specific traits that may contribute to those differ ences. A tall hybrid was more tolerant to A. theophrasti interference than two medium stature hybrids. Early leaf area growth of two medium-stature sorghum hybrids was reduced by A. theophrasti interference, whereas early growth of a tall hybrid was unaffected. The height of A. theophrasti was greater than two moderate-stature hybrids but lower than the tall hybrid. Greatest leaf area density (L D ) of the tall sorghum hybrid was above that of A. theophrasti, whereas greatest L D of medium-stature hybrids was below that of the weed. In monoculture, the partitioning of new biomass to various plant organs was similar among sorghum hybrids, whereas the tall sorghum hybrid partitioned less biomass to leaves and more to stems than medium hybrids in mixture. The results indicate that the three hybrids differ in their susceptibility to A. theophrasti competition. Crop traits that may contribute to greater crop competitiveness include greater maximum height and its growth rate and greater height of maximum leaf area distribution.

For most studies involving the response of plants to future concentrations of atmospheric carbon dioxide (CO2), a current concentration of 360–370 μatm is assumed, based on recent data obtained from the Mauna Loa observatory. In the present study, average seasonal diurnal values of ambient CO2 obtained at ground level from three global locations (Australia, Japan and the USA) indicated that the average CO2 (at canopy height) can vary from over 500 μatm at night to 350 μatm during the day with average 24-h values ranging from 390 to 465 μatm. At all sites sampled, ambient CO2 rose to a maximum value during the pre-dawn period (03.00–06.00 hours); at sunrise, CO2 remained elevated for several hours before declining to a steady-state concentration between 350 and 400 μatm by mid-morning (08.00–10.00 hours). Responses of plant growth to simulations of the observed variation of in situ CO2 were compared to growth at a constant CO2 concentration in controlled environment chambers. Three diurnal patterns were used (constant 370 μatm CO2, constant 370 during the day (07.00–19.00 hours), high CO2 (500 μatm) at night; or, high CO2 (500 μatm) at night and during the early morning (07.00–09.00 hours) decreasing to 370 μatm by 10.00 hours). Three plant species − soybean (Glycine max, L (Merr.), velvetleaf (Abutilon theophrasti L.) and tomato (Lycopersicon esculentum L.) − were grown in each of these environments. For soybean, high night-time CO2 resulted in a significant increase in net assimilation rate (NAR), plant growth, leaf area and biomass relative to a constant ambient value of CO2 by 29 days after sowing. Significant increases in NAR for all three species, and significant increases in leaf area, growth and total biomass for two of the three C3 species tested (velvetleaf and soybean) were also observed after 29 days post sowing for the high night/early morning diurnal pattern of CO2. Data from these experiments suggest that the ambient CO2 concentration experienced by some plants is higher than the Mauna Loa average, and that growth of some agricultural species at in situ CO2 levels can differ significantly from the constant CO2 value used as a control in many CO2 experiments. This suggests that a reassessment of control conditions used to quantify the response of plants to future, elevated CO2 may be required.

Two mycotrophic species (Lactuca sativa and Abutilon theophrasti) and one nonmycotrophic species (Beta vulgaris) were grown in a P-deficient soil, and the effects of mycorrhizal inoculation on three variables that determine growth rate were assessed for each. The phosphorus-use efficiency (PUE, dW/dP) is the ratio of d. wt increase to P content increase. Plant P is the amount of P (the limiting resource) controlled by the plant, which can be allocated to various purposes. The phosphorus efficiency index (PEI, dP/Pdt) is the efficiency with which plant P is used to acquire P from the soil. Inoculated and control plants of a given species initially contained the same amount of P because all plants were grown from seed. Mycorrhizal colonization significantly increased the PEI of Lactuca and Abutilon (by 23 and 32%, respectively). As expected, mycorrhizal inoculation did not significantly increase the PEI of Beta. As a result, mycorrhizal inoculation significantly increased the P content of Lactuca and Abutilon, but not Beta. Mycorrhizal colonization decreased the PUE of lettuce, but did not significantly affect that of Abutilon or Beta. Mycorrhizal inoculation therefore slightly increased the growth rate of Lactuca, greatly increased the growth rate of Abutilon, and ultimately had no significant effect on the growth rate of Beta.

It is well known that ammonium sulphate (AMS) overcomes the antagonistic effect of cations found in hard water on glyphosate activity. In this paper we examine the effect of AMS on glyphosate-trimesium activity when sprayed in deionised water and following hydroponic application to roots of two tolerant broadleaved weeds (Abutilon theophrasti Medik and Convolvulus arvensis L) and one susceptible grass (Sorghum halepense L). The increase in activity from foliar sprays with AMS was greatest on A theophrasti, followed by C arvensis, with no significant improvement on S halepense. Following root treatment of the same weed species, glyphosate-trimesium showed a marked increase in activity against A theophrasti with AMS, with lower levels of enhancement on the other two species. This matched the higher calcium content of A theophrasti (3.1% dry weight) compared to C arvensis (1.5%) and S halepense (1.0%). Scanning electron microscopy and X-ray microanalysis were used to identify the presence of antagonistic elements (Mg and Ca) on leaf surfaces of A theophrasti. Misting of leaf surfaces promoted the leaching of substances rich in calcium from within the leaf on to the surface. In addition, species such as A theophrasti have specialised trichomes known as chalk glands which are a source of cations. Data are presented which show that, in uptake studies with [14C]glyphosate-trimesium, anomalous results may be found unless an acidified wash solution is used to remove residual surface material, which remains as an insoluble deposit with aqueous methanol washing. It is proposed that the reduced potency shown by glyphosate on certain species such as A theophrasti can be partially explained by the interaction of the herbicide anion with antagonistic cations both on and within the plant. © 2000 Society of Chemical Industry

Infection with phloem limited Abutilon Mosaic Virus caused localized carbohydrate accumulation (high levels of starch, sucrose, and hexoses) in leaves of Abutilon striatum during early symptom development. In mature leaves with attenuated symptoms, tissues showing faint vein-clearing had markedly higher carbohydrate contents than uniformly green areas of the same leaf. A similar pattern of carbohydrate accumulation was found in pale-green mosaics in mature leaves with overt symptoms when compared to green-islands of the same leaf, but overnight carbohydrate loses were comparable to controls. Because leaves with attenuated symptoms showed no further symptom development whereas the pale-green mosaics became yellow and eventually necrotic in leaves with overt symptoms, it seems unlikely that carbohydrate accumulation following impaired translocation was responsible for symptom expression. High carbohydrate status in leaves with attenuated symptoms had little effect on nonphotochemical quenching during early stages of photosynthetic induction. In leaves with overt symptoms, areas of high carbohydrate status with pale-green mosaics showed markedly slower nonphotochemical quenching. Early symptom areas of young leaves, and advanced symptom areas of mature leaves had low starch contents but were otherwise similar to controls in carbohydrate status. Impaired nonphotochemical quenching in these tissues tended to reflect the state of symptom development, rather than carbohydrate status. Plants with overt symptoms grew about half as fast as plants with attenuated symptoms.

Summary Interactive effects of CO2 and water availability have been predicted to alter the competitive relationships between C3 and C4 species over geological and contemporary time scales. We tested the effects of drought and CO2 partial pressures (pCO2) ranging from values of the Pleistocene to those predicted for the future on the physiology and growth of model C3 and C4 species. We grew co-occurring Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture at 18 (Pleistocene), 27 (preindustrial), 35 (current), and 70 (future) Pa CO2 under conditions of high light and nutrient availability. After 27 days of growth, water was withheld from randomly chosen plants of each species until visible wilting occurred. Under well-watered conditions, low pCO2 that occurred during the Pleistocene was highly limiting to C3 photosynthesis and growth, and C3 plants showed increased photosynthesis and growth with increasing pCO2 between the Pleistocene and future CO2 values. Well-watered C4 plants exhibited increased photosynthesis in response to increasing pCO2, but total mass and leaf area were unaffected by pCO2. In response to drought, C3 plants dropped a large amount of leaf area and maintained relatively high leaf water potential in remaining leaves, whereas C4 plants retained greater leaf area, but at a lower leaf water potential. Furthermore, drought-treated C3 plants grown at 18 Pa CO2 retained relatively greater leaf area than C3 plants grown at higher pCO2 and exhibited a delay in the reduction of stomatal conductance that may have occurred in response to severe carbon limitations. The C4 plants grown at 70 Pa CO2 showed lower relative reductions in net photosynthesis by the end of the drought compared to plants at lower pCO2, indicating that CO2 enrichment may alleviate drought effects in C4 plants. At the Pleistocene pCO2, C3 and C4 plants showed similar relative recovery from drought for leaf area and biomass production, whereas C4 plants showed higher recovery than C3 plants at current and elevated pCO2. Based on these model systems, we conclude that C3 species may not have been at a disadvantage relative to C4 species in response to low CO2 and severe drought during the Pleistocene. Furthermore, C4 species may have an advantage over C3 species in response to increasing atmospheric CO2 and more frequent and severe droughts.

Combining empirical research with simulation modeling may improve our understanding of the dynamics of crop:weed competition and for testing hypotheses on the importance of specific traits for enhancing crop performance in mixtures. Two field experiments were conducted to quantify and compare estimates of traits important for radiation interception and utilization in four maize hybrids and Abutilon theophrasti grown in monoculture. Early leaf area growth rate did not vary among maize hybrids within a year, but varied among years. The response of CO 2 assimilation rate to absorbed radiation and leaf nitrogen content did not differ among hybrids. Abutilon theophrasti and two old maize hybrids partitioned more new biomass to stem relative to reproductive organs than newer hybrids. Old hybrids had greater specific leaf area during the period of most rapid growth, grew taller, and leaf area was distributed higher in their canopy. Extinction coefficients for diffuse radiation did not differ among hybrids or between years. Results suggest that these four maize hybrids may differ in their ability to intercept incident radiation, which may influence their ability to compete for light.

An experimental approach was used to examine the effects of spatial nutrient heterogeneity and planting density on the sizes of plants within populations of Abutilon theophrasti. Planting locations were generated using random numbers and replicated among populations growing on two different scales of heterogeneity and homogeneous soils. The same quantity of nutrients (dehydrated cow manure) was added to each population, regardless of the spatial nutrient distribution. The higher density was achieved by adding additional planting locations to those present at the lower density. Plant biomass was compared among ten planting locations present in all populations. Plants in seven locations were smaller at the higher density, but the spatial distribution of nutrients affected plant size in only two locations. At the population level, the higher density reduced mean plant biomass and increased both total biomass and the coefficient of variation in biomass, a measure of size inequality. Only when populations on both scales of heterogeneity were together compared with those on homogeneous soils were population-level measurements found to be significantly affected by soil treatment; heterogeneity resulted in decreased total biomass and an increase in the coefficient of variation, apparently due to an increase in the number of small plants in the population. These results, together with the finding that fine root biomass increased in nutrient-enriched patches, suggest that on heterogeneous soils most plants were able to access nutrient patches.

Crops that better tolerate weed competition or preempt resources from weeds may reduce dependence on herbicides for weed control and benefit an integrated weed management program. Irrigated field experiments were conducted to identify morphological traits of corn (Zea mays L.) that enhance its tolerance and weed suppressive ability. Two old (circa 1940) and two modern corn hybrids were grown in mixture with five target densities of velvetleaf (Abutilon theophrasti Medik.) in two years. Corn height and leaf area index (LAI) were measured periodically throughout the growing season. Vertical leaf area distribution was measured at corn anthesis. Quantitative estimates of these traits were obtained for each experimental unit using linear and nonlinear regression analysis. Magnitude of the correlation between these trait estimates and corn yield reduction in mixture with velvetleaf or velvetleaf seed capsule production was used as an indicator of the importance of each trait to the enhancement of corn tolerance or velvetleaf suppressive ability. Canopy traits having highest correlation with corn relative yield in 1995 were maximum LAI (r = -0.38) and crop density (r = -0.24). Those with highest correlation in 1996 were crop density (r = -0.36), degree days accumulated between emergence and 50% maximum height (r = 0.34) and LAI (r = 0.19), and vertical leaf area distribution (0.49). Corn canopy traits were not correlated with velvetleaf seed production in 1995. However, vertical leaf area distribution (r = 0.60), maximum LAI (r = 0.32), and corn density (r = -0.26) were correlated with velvetleaf seed production in 1996. Results suggest that increasing maximum corn LAI, rate of canopy closure, or height at which leaf area occurs in the canopy can improve corn tolerance and velvetleaf suppressive ability. These traits can be modified by varying cultural practices such as row spacing and population density, or through breeding.

A portable Chi fluorescence imaging system was used to characterise nonuniform Chi fluorescence quenching in Abutilon striatum leaves infected with phloem-localised abutilon mosaic virus. The instrument was used to observe fluorescence emission at intervals during induction transients, and to map nonphotochemical quenching during saturating pulses applied in the course of these transients. Two symptom types were distinguished: yellow vein-associated motifs that showed lower maximum Chi fluorescence than nearby green tissues, but virtually zero nonphotochemical quenching, and vein-defined mosaics (pale green) that initially showed normal maximum Chi fluorescence but strongly impaired nonphotochemical quenching. Mature vein-defined mosaics (yellow to white areas) resembled vein-associated symptoms with zero nonphotochemical quenching. Islands of apparently healthy green tissue enclosed by mosaic symptoms showed slower nonphotochemical quenching than controls. Possible effects of localised carbohydrate accumulation, thought to follow from infection by the phloem-limited virus, on photosynthetic processes as well as the synthesis and stability of chloroplast protein complexes, are discussed in the context of symptom development.

We tested whether plants allocate proportionately less biomass to roots in response to above-ground competition as predicted by optimal partitioning theory. Two population densities of Abutilon theophrasti were achieved by planting one individual per pot and varying spacing among pots so that plants in the two densities experienced the same soil volume but different degrees of canopy overlap. Density did not affect root∶shoot ratio, the partitioning of biomass between fine roots and storage roots, fine root length, or root specific length. Plants growing in high density exhibited typical above-ground responses to neighbours, having higher ratios of stem to leaf biomass and greater leaf specific area than those growing in low density. Total root biomass and shoot biomass were highly correlated. However, storage root biomass was more strongly correlated with shoot biomass than was fine-root biomass. Fine-root length was correlated with above-ground biomass only for the small subcanopy plants in crowded populations. Because leaf surface area increased with biomass, the ratio between absorptive root surface area and transpirational leaf surface area declined with plant size, a relationship that could make larger plants more susceptible to drought. We conclude that A. theophrasti does not reallocate biomass from roots to shoots in response to above-ground competition even though much root biomass is apparently involved in storage and not in resource acquisition.

1. Our goal was to determine whether mycorrhizal infection of one generation of plants could influence the competitiveness of the subsequent generation. 2. We grew the offspring of mycorrhizal (M) and non-mycorrhizal (NM) Abutilon theophrasti plants together in dense populations in large boxes in a greenhouse. 3. Offspring of M plants were larger than offspring of NM plants. As the experiment progressed, the difference in size was magnified and self-thinning occurred. 4. Compared with offspring of NM plants, offspring of M plants had a twofold greater survival and collectively produced a total of nearly four times as many seeds. 5. We conclude that mycorrhizal infection of the parent generation can increase the competitive ability of the offspring.

We studied the effects of CO2 elevation on leaf and canopy photosynthesis and optimal leaf area index (LAI) for stands of the annual species Abutilon theophrasti and Ambrosia artemisiifolia. Leaf photosynthesis was modeled as a function of photosynthetic photon flux density (PPFD) and nitrogen content per unit leaf area (NL). There was a curvilinear relationship between the light-saturated rates of leaf photosynthesis (Pmax) and NL. CO2 elevation significantly increased Pmax as a function of NL in both species. Dark respiration (Rd) was linearly correlated with NL. CO2 elevation slightly but significantly increased Rd in Abutilon, while it had no significant effect on Rd in Ambrosia. The initial slope of a light-response curve was determined from quantum yield (ϕabs) multiplied by leaf absorptance and then calibrated against NL. Daily canopy photosynthesis, calculated by integration of leaf photosynthesis with the actual distribution of leaf area, leaf N, and PPFD within a canopy, showed fairly good agree...

Post-emergence application of carfentrazone-ethyl at rates as low as 2.2 g ha -1 caused greater leaf injury and growth reduction in ivyleaf morningglory (Ipomoea hederacea) and velvetleaf (Abutilon theophrasti) than in soybean (Glycine max). The herbicide was more rapidly metabolized in the crop than in the weed species, with 26.7, 54.3 and 60.6% of the parent compound remaining in soybean, ivyleaf morningglory and velvetleaf, respectively, 24 h after exposure. The free acid metabolite, carfentrazone, was present in all species and accounted for 21.2-27.4% of the total radioactivity. Unknown metabolites (R f 0 and 0.22) were four to five times more abundant in soybean than in the weed species. Carfentrazone-ethyl induced more leakage from leaf discs from the weeds than those from soybean and the degree of injury correlated with the amount of protoporphyrin IX (Proto IX) present in the treated tissues. Both carfentrazone-ethyl and carfentrazone were potent inhibitors of protoporphyrinogen oxidase (Protox). Therefore, the selectivity of this herbicide may, at least in part, be attributed to the lower accumulation of Proto IX in soybean than in the weeds, probably because of the ability of soybean to metabolize more carfentrazone into unknown metabolites than the weeds.

Summary Tillage causes both vertical redistribution of weed seeds and changes in soil physical properties. These two factors are rarely distinguished in studies of the impact of tillage on seedling emergence or seed survival. In this study, seeds of Chenopodium album L., Amaranthus retroflexus L., and Abutilon theophrasti Medik, were planted at particular depths in pots of undisturbed or stirred soil to separate these effects. Emergence and survival data were analysed by non-linear regression to determine the nature of significant differences between treatments. Emergence increased with slight burial and then decreased exponentially at greater depths. Average emergence over all depths was generally greater in tilled sou than in unfilled soil, particularly for C. album and A. retroflexus. Seed survival approached a maximum with increasing depth. Average survival of seeds that did not produce emerged seedlings was greater in tilled soil than in untilled soil for C. album and A. retroflexus. Thus, tillage affects emergence and seed survival of weeds through changes in soil conditions independently of effects resulting from redistribution of seeds in the soil profile.

Summary Twelve species were identified as having been introduced into Morocco since 1980. These were Abutilon theophrasti Medik., Ammannia coccinea Griseb. Brachiaria eruciformis (Smith) Griseb. Corchorus olitorius L. Cyperus difformis L., Dactyloctenium aegyptium (L.) Richt., Echinochloa phyllopogon (Stapf) Koss, Euphorbia heterophylla L., Kochia scoparia (L.) Schrad., Panictun capillare L., Solanum cornutum Lam, and S. elaeagnifolium Cav. They were possibly introduced with contaminated crop seeds. With the exception of S. cornutum, which has disappeared from the site where it was first collected in 1987, the other species are becoming major weeds in one or more provinces. Details of their biology and importance are discussed.

Summary Seeds of Abutilon theophrasti Medic., collected from plants growing in a continuous maize or soyabean field subjected to herbicide application, cultivation or no weed management for 10 years, differed significantly in their weight and germinability. The differences in mean weight and germinability of the progeny seeds were maintained when the parent plants were grown in a greenhouse under controlled conditions. The offspring of plants with or without previous exposure to atrazine responded similarly to the herbicide in all the measurements of the growth and development of the plants, except blooms. Significant differences between the two groups of plants were mainly observed in the weight and germinability of their seeds. Although plants with or without previous exposure to atrazine usually did not differ significantly in their response to the herbicide in terms of individual traits, they differed both in the amount and pattern of overall response across all traits. The difference in overall response between plants increased with increasing rate of atrazine. It is possible that previous exposure to the herbicide had caused minor variation in a group of inter-correlated traits or in the strength or pattern of correlation among traits.

summary In previous studies we demonstrated that for Abutilon theophrasti Medic, offspring of mycorrhizal plants grew more rapidly than did offspring of non-mycorrhizal plants. This observation was verified in the current study. We hypothesized that the faster growth of offspring of mycorrhizal plants was caused by a superior ability to absorb nutrients, since offspring of mycorrhizal plants produced faster-growing root systems with higher phosphatase activities. We tested the hypothesis by growing offspring plants in distilled water. Despite the absence of any nutrients short-term growth rates of offspring of mycorrhizal plants were still significantly greater than those of offspring of non-mycorrhizal plants. We conclude that the faster growth of offspring of mycorrhizal plants is nor caused by a superior ability to acquire external resources.

summary The combined effects of planting density and of different inoculation frequencies ofColletotrichum coccodes (Wallr.) Hughes on growth and competitive performance of Abutilon theophrasti Medik. were studied using a soybean-A. theophrasti target-neighbour design in a controlled environment. In both trials of the experiment, A. theophrasti inoculated at the highest planting density (four plants per ppt) suffered significantly greater reductions in height (41%) than did A. theophrasti at the lowest density (one plant per pot) (7%). Above-ground biomass and leaf area reductions, however were significantly greater at the highest density for only one of the trials. Soybean plants grown with inoculated A. theophrasti at the two highest planting densities had a significantly greater above-ground biomass (61%) and leaf area (68%) than did plants grown with uninoculated A. theophrasti at the same densities. By contrast, at the two lower densities, soybean above-ground biomass and leaf area were not increased significantly fallowing inoculation. Either one or two C. coccodes inoculations caused the greatest reductions in A. theophrasti growth compared with uninoculated plants. Conversely, three applications of the fungus generally resulted in less severe disease symptoms and resulted in the smallest decreases in A. theophrasti growth. Induced systemic resistance following two inoculations might have played an important role in limiting disease. However, the significantly greater biomass and height of A. theophrasti plants subjected to the triple C. caicudes treatment, compared with plants receiving either one or two inoculations in one of the trials, provides some evidence of a possible compensatory response in .4. theophrasti. The relevance of these findings for biological weed control is examined.

Weed control in corn (Zea 'nays) and soybean [Glycine mar (L.) Merr.] with band applications of herbicides plus cultivation was evaluated in these studies. Giant foxtail (Setaria faberi Herrm.) and velvetleaf (Abutilon theophrasti Medik) control in corn with band applications plus cultivation was equal to or better than control with broadcast applications without cultivation of the same herbicides 2 of the 3 yr. Ivyleaf morningglory [Ipomoea hederacea (L.) Jacq.] control was less consistent with band applications plus cultivation than with the broadcast applications. There was no difference in yellow nutsedge (Cyperus esculentus L.) control between the band applications plus cultivation and broadcast applications averaged over years. Giant foxtail, velvetleaf, ivyleaf morningglory, common cocklebur (Xanthium strumarium L.), and yellow nutsedge control in soybean with band application plus cultivation was equal to or better than the control with the broadcast application of the same herbicides without cultivation. Corn and soybean yields were related to the level of weed control. Weed control costs in corn and soybean were lower with the band application plus two cultivations than with the broadcast application of the same herbicides. Band application plus cultivation reduced the total amount of herbicide applied per acre by 66%.

In a pair of similar experiments, we examined the effects of varying substrate nutrient levels on several measures of male and female function in Abutilon theophrasti (Malvaceae). In the first trial, plants adjusted allocation to female function at several levels: number of flowers initiated, locule number, percentage of fruits matured, and percentage of ovules matured. In the second trial, plants were much larger, opened more flowers, and matured more fruit (in total but not on a percentage basis). However, in response to nutrient level, plants adjusted maternal investment at fewer levels than in the first trial. Seed mass varied between, but not within, trials. Little to no adjustment was seen in male characters within either trial, although flower number differed within trials and stamen number differed between trials. The lack of adjustment of paternal investment may be due to the fact that A. theophrasti is primarily an autogamous species. Between the two trials, growing conditions, primarily light intensity, varied and plants adjusted their allocation to reproduction differently, indicating plasticity in this trait. theophrasti and that offspring ofthe plants grown at higher nutrient levels generally had greater competitive abilities. Similarly, Erodium brachycarpum was found to adjust seed size based on soil moisture content, and larger seeds, produced in wetter environments, had a competitive ad- vantage over smaller seeds (Stamp, 1990). Vasek et al. (1987) found a positive relationship between seed number and nutrient level in Clarkia, and a reduction in seed number (but not mass) was caused by stressing Lobelia plants by shading them (Devlin, 1988). In general, the fitness effects of seed size are well documented (McGinley, Temme, and Geber, 1987), and suggest that seed size, as well as number, affects fitness achieved through female

The genus Abutilon (Malvaceae) comprises about 150 species which are perennial herbs, shrubs and rarely small trees, distributed in sub-tropical regions of all over the world. Generally, Abutilon species contain considerable amounts of mucilage due to which they are used for the treatment of rheumatism and as demulcent and diuretic agents [1 – 3]. One of the species of the genus Abutilon is Abutilon pakistanicum which commonly grows in the southern parts of Pakistan. The literature survey revealed that steroids [4, 5], esters, flavonoid glycosides [6, 7], and iridoids [8] have so far been reported from this species. The ethnopharmacological and chemotaxonomic importance of the genus Abutilon led us to further investigate the chemical constituents of A. pakistanicum. We herein report the isolation and structural elucidation of two new sphingolipids named pakistamides A (1) and B (2).

Summary: Resume: Zusammenfassung Relations between availability of light and reproductive activity in several of the most damaging summer weeds (Abutilon theophrasti Medicus, Datura stramonium L., Sorghum halepense L. Pers.) were studied, in order to investigate seed production capacity of these weed species in the unfavourable conditions occurring under a crop canopy simulated by shade cloths. Decrease in seed production under shading appeared to be due to a decrease in the number of fruits per plant, while the quantity of seed per fruit proved to be fairly stable. Biomass partitioning within the plant reduced the percentage of dry matter accumulated in reproductive organs, leading to a marked decrease in the harvest index. Further-more, shading caused a species-dependent delay in onset of the flowering and ripening stages. In Datura stramonium shading led to a greater de-crease in seed production and, consequently, in the harvest index than in the other species examined. Finally, laboratory tests demonstrated that the percentage of dormant seeds remained unmodified in all species examined. Effet de l'ombragesur la reproduction et quelques caracteristiques morphologiques de Abutilon theophrasti Medicus, Datura stramonium E. et Sorghum halepense L. Pers. Les relations entre la fourniture de lumiere et l'activite reproductrice de quelques unes des mauvaises herbes les plus importantes (Abutilon tiieophrasti Medicus, Datura stramonium L., Sorghum halepense L. Pers.) ont eteetudiees en vue de determiner leur capacitea produire des graines dans les conditions defavorables qui prevalent sous les couverts vegetaux. La diminution de la production de graines etait due a une diminution du nombre de fruit par plante, alors que la quantite de graines par fruits restait a peu pres stable. La distribution de la biomasse dans la plante conduisait a une diminution du pour-centage de matiere seche accumulee dans les organes reproducteurs, ce qui se traduisait par une diminution de l'indice de recolte. De plus, l'ombrage causait un retard (variable selon l'espece) du debut de la floraison et de la maturation. Chez Datura stramonium, l'ombrage conduisait a la reduction la plus importante de la production de graines (et par consequent de l'indice de recolte). Enfin, des tests en laboratoire ont montre que le pourcentage de graines dormantes n'etait modifie chez aucune des especes testees. Einflus von Beschattung auf Vermehrung und morphologische Eigenschaften von Abutilon theophrasti Medicus, Datura stramonium E. und Sorghum halepense (E.) Pers. An einigen sommerannuellen Unkrautem (Abutilon theophrasti Medicus, Datura stramonium L. und Sorghum halepense (L.) Pers.) wurde die Beziehung zwischen der Lichtverfugbarkeit und der Samenproduktion dieser Arten unter den ungunstigen Bedingungen der Beschattung in einem Kulturpflanzenbestand, die durch Beschattungsgewebe simuliert wurde, untersucht. Die Abnahme der Samenproduktion bei Beschattung ist durch die geringere Fruchtzahl pro Pflanze bedingt; die Samenzahl pro Frucht erwies sich als ziemlich stabil. Die Biomasseverteilung in den Pflanzen fuhrte zu einer Abnahme der Trockenmasse der Reproduktionsorgane und damit zu einem deutlich kleineren Ertragsindex. Auserdem wurden durch die Beschattung der Bluhbeginn und das Reifestadium verzogert. Bei Datura stramonitim war die Abnahme der Samenbildung und somit des Ertragsindex starker als bei den anderen Arten. Der Anteil dormanter Samen blieb bei alien Arten durch die Beschattung einbeeinflust.

Mycorrhizal infection of Abutilon theophrasti Medic, increased seed quality and resultant offspring performance, but the improvement varied significantly with the timing of seed production. In general, offspring from mycorrhizal plants were superior to offspring from non-mycorrhizal plants, but the difference was greatest for the early cohort of seeds. Because increased seed size and quality can affect subsequent offspring competitive ability, increased variability in seed size and quality due to mycorrhizal infection may have an important impact on population dynamics of A. theophrasti.

Summary: Resume: Zusammenfassung The influence of several experimental parameters (time, concentration, pH, and temperature) on cellular absorption of cycloxydim was studied using suspension–cultured velvetleaf (Abutilon theophrasti Medic.) cells. Cycloxydim and its metabolites accumulated in cells to a concentration higher than that of the external medium. Metabolism was rapid with 88.6 % conversion to metabolites within 6 h. Cycloxydim absorption was linearly related to the external cycloxydim concentration, indicating that cycloxydim absorption across cell membranes occurs by passive diffusion. Absorption was strongly pH–dependent, with more intracellular cycloxydim plus metabolites accumulating at acidic extracellular pH, indicating an ion–trap mechanism of absorption. Cycloxydim absorption was significantly higher at 20°C compared with 4 and 12°C, but no difference existed between the last two temperatures. Studies of the influence of three adjuvants (Armoblen T/25, BanDrift, and ammonium sulfate) on cycloxydim absorption demonstrated that BanDrift at 0.01% (v/v) and ammonium sulfate at 1.0 and 10 mM increased cycloxydim absorption at all times. However, Armoblen T/25 at 0.002% (v/v) increased cycloxydim absorption at only a short incubation time (30 min). Absorption du cycloxydime par des cultures de cellules d'Abutilon theophrasti Medic. L'influence de plusieurs parametres experimentaux (temps, concentration, pH et temperature) sur l'absorption du cycloxydime par des suspensions cellulaires de jute de Chine (Abutilon theophrasti Medic.) a eteetudiee. Le cycloxydime et ses metabolites s'accumulaient dans les cellules a une concentration superieure a celle du milieu exterieur. La metabolisation etait rapide avec 88.6 % de conversion en metabolites en 6 h. L'absorption de cycloxydime etait lineaire en fonction de sa concentration externe, indiquant qu'il s'agit d'un phenomene passif. Elle etait fortement dependante du pH, les pH externes acides favorisant l'accumulation intracellulaire de cycloxydime et de ses metabolites, ce qui indique un mecanisme d'absorption a piegeage d'ions. L'absorption du cycloxydime etait significativement superieure a 20°C, comparea 4 et 12°C, mais aucune difference n'etait detectable entre les deux dernieres temperatures. L'adjuvant BanDrift 0–01 % (v/v) et le sulfate d'ammonium 1 et 10 mM augmentaient l'absorption du cycloxydime a tous les temps d'incubation. L'adjuvant Armoblen T/25 0.002 % (v/v) ne l'augmentait que pour des temps d'incubation courts (30min). Absorption von Cycloxydim in Zellsuspensionen von Abutilon theophrasti Medic. Der Einflus verschiedener Versuchsparameter (Zeit, Konzentration, pH und Temperatur) auf die Absorption von Cycloxydim in Zellen wurde mit Zellsuspensionen von Abutilon theophrasti Medic. untersucht. Cycloxydim und seine Metaboliten wurden in den Zellen in hoherer Konzentration als im Umgebungsmedium akkumuliert. Die Metabolitenbildung verlief schnell (88.6 % in 6 h). Die Absorption des Wirkstoffs stand in linearer Beziehung zu der auseren Konzentration, was zeigt, das die Absorption durch passive Diffusion ablauft. Sie war streng pH-abhangig.

SUMMARY The effects of inoculation with mycorrhizal fungi and phosphorus amendment on reproduction of Abutilon theophrasti Medic, were documented over two years in the field. In Year 1 all plots were thinned to a common and relatively low density (12 plants m−2). Mycorrhizal infection significantly increased capsule and seed production. Phosphorus amendment had little effect on these characters, possibly due to low soil moisture content. In Year 2 following natural recruitment, inoculated (M) plots were much more dense than uninoculated (NM) plots. In contrast with the results from Year 1, however, individual plains in M plots produced fewer capsules than those in NM plots in Year 2 because capsule production in Year 2 was density-dependent. Based on these results and others, we suggest that in monospecific stands of Abutilon, mycorrhizal infections have the greatest effects on fecundity at low densities. At higher densities, density-dependent forces may reduce the importance of mycorrhizal infections to reproductive effort of a single plant. Our results highlight the necessity of examining the effects of mycorrhizal fungi in natural populations and communities.

Summary: Resume: Zusammenfassung Effects of temperature and three adjuvants (ammonium sulphate, Armoblen T/25, and BanDrift) on absorption of glyphosate by suspension-cultured velvetleaf (Abutilon theo phrasti) cells were examined. Velvetleaf cells absorbed glyphosate to a concentration about 40% of the external media concentration following incubation for 3 h. Ammonium sulphate at concentrations of 0.1 mM to 10.0 mM did not significantly affect glyphosate absorption. The results were similar for Armoblen T/25. However, Armoblen T/25 was toxic to the cells at concentrations as low as 0.002% (v/v). BanDrift showed no toxicity to the cells, but significantly increased glyphosate absorption. This stimulation of glyphosate absorption was present at 4°C as well as 28°C. Effets d'adjuvants et de la temperature surl'absorption du glyphosate par des cellules cultivees de jute de Chine (Abutilon theophrasti Medic.) Les effets de la temperature et de 3 adjuvants (sulfate d'ammonium, Armoblen T/25 et BanDrift) sur l'absorption du glyphosate par une culture en suspension de cellules de jute de Chine (Abutilon theophrasti) ont eteetudiees. Les cellules de jute de Chine ont absorbe le glyphosate a une concentration voisine de 40% de la concentration du milieu externe apres une incubation de 3 heures. Le sulfate d'ammonium a des concentrations de 0,1 mM a 10 mM n'a pas significativement affecte l'absorption du glyphosate. Les resultats ont ete similaires avec l'Armoblen T 25. Cependant, l'Armoblen T/25 etait toxique pour les cellules a des concentrations aussi faibles que 0,002% (v/v). Le BanDrift n'a pas exprime de toxicite vis-a-vis des cellules mais a significativement fait augmenter l'absorption du glyphosate. Cette stimulation de l'absorption du glyphosate etait presente a 40 °C tout comme a 28°C. Wirkung von Zusatzstoffen und Temperatur auf die Absorption von Glyphosat in Zellkulturen der Samtpappel (Abutilon theophrasti Medic.) Die Wirkung der Temperatur und von 3 Zusatzstoffen (Ammoniumsulfat, Armoblen T/25, BanDrift) auf die Absorption von Glyphosat in Zellkultursuspensionen der Samtpappel (Abutilon theophrasti) wurde untersucht. Innerhalb 3 h absorbierten die Zellen Glyphosat bis zu 40% der Konzentration im Medium. Nach Zugabe von 0,1 bis 10,0 mM Ammoniumsulfat wurde die Glyphosatauf-nahme nicht signifikant beeinflust. Bei Armoblen T/25 waren die Ergebnisse ahnlich, doch war dieser Zusatzstoff schon bei 0,002 Vol.-% toxisch. BanDrift war nicht toxisch und erhohte die Absorption signifikant, sowohl bei 4 als auch bei 28 °C.

Summary Selected monoclonal antibodies (MAbs), prepared to particles of African cassava mosaic or Indian cassava mosaic geminiviruses, detected three geminiviruses that occur in Europe: abutilon mosaic virus in Abutilon pictum ‘Thompsonii’, tobacco leaf curl virus in Lonicera japonica var. aureo-reticulata and tomato yellow leaf curl virus in Lycopersicon esculentum. All three viruses were detected in indirect ELISA by MAbs SCR 17 and SCR 20 but they were differentiated by their reactions with SCR 18 and SCR 23. Tobacco leaf curl virus was detected only when reducing agents were included in the leaf extraction medium. Inclusion of sodium sulphite slightly improved detection of tomato yellow leaf curl virus but reducing agents were not needed for detection of abutilon mosaic virus.

Two genets of Abutilon theophrasti were clonally replicated and grown to maturity in a glasshouse at two levels of nutrient supply. The seeds produced were weighed and the resulting seedlings exposed to two nutrient levels during development. The progeny plants were harvested on three occasions, and leaf areas and dry weights of the different plant parts were determined. At the early stages of growth an increase in the maternal nutrient supply significantly increased seedling height, cotyledon area, and leaf areas, and seed weight had a significant effect on several traits. The maternal nutrient addition had no significant effect at a later stage of growth (35 d after sowing), but at 56 d after sowing it did affect offspring leaf areas and dry weights. Significant interaction terms indicate that the response to parental nutrient addition may depend both on genotype and on the nutrient status of the progeny. Different plant characters are differentially sensitive to maternal conditions and these may be expressed at different stages of development.

We examined how CO2 concentrations and temperature interacted to affect growth, resource acquisition, and resource allocation of two annual plants that were supplied with a single pulse of nutrients. Physiological and growth measurements were made on individuals of Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) grown in envi- ronments with atmospheric CO2 levels of 400 or 700 gtL/L and with light/dark temperatures of 28?/22? or 380/3 10C. Elevated CO2 and temperature treatments had significant indepen- dent and interactive effects on plant growth, resource allocation, and resource acquisition (i.e., photosynthesis and nitrogen uptake), and the strength and direction of these effects were often dependent on plant species. For example, final biomass of Amaranthus was enhanced by elevated CO2 at 280 but was depressed at 380. For Abutilon, elevated CO2 increased initial plant relative growth rates at 280 but not at 380, and had no significant effects on final biomass at either temperature. These results are interpreted in light of the interactive effects of CO2 and temperature on the rates of net leaf area production and loss, and on net whole-plant nitrogen retention. At 280C, elevated CO2 stimulated the initial production of leaf area in both species, which led to an initial stimulation of biomass accumulation at the higher CO2 level. However, in elevated CO2 at 280, the rate of net leaf area loss for Abutilon increased while that of Amaranthus decreased. Furthermore, high CO2 apparently enhanced the ability of Amaran- thus to retain nitrogen at this temperature, which may have helped to enhance photosyn- thesis, whereas nitrogen retention was unaffected in Abutilon. Thus, at 280, final biomass of Abutilon was not stimulated in a high CO2 environment whereas the final biomass of Amaranthus was. At 380, Abutilon had slightly reduced peak leaf areas under elevated CO2 in comparison to ambient CO2 grown plants, but increased rates of photosynthesis per unit leaf area early in the experiment apparently compensated for reduced leaf area. For Amaran- thus at 380, peak leaf area production was not affected by CO2 treatment, but the rate of net leaf area loss hastened under elevated CO2 conditions and was accompanied by sub- stantial reductions of whole-plant nitrogen content and leaf photosynthesis. This may have led to the reduced biomass accumulation of high CO2 grown plants that we observed during the last 30 d of growth. Plants of both species grown in elevated CO2 exhibited reduced tissue-specific rates of nitrogen absorption, increased plant photosynthetic rate per unit of conductance, and increased initial allocation of biomass to roots, irrespective of temperature. Plants of both species grown under an elevated temperature regime had substantially decreased repro- ductive allocation, increased allocation to stem biomass, and increased plant water flux at both CO2 treatments. The age of plants also affected our interpretations of plant responses to CO2 and temperature treatments. For example, significant effects of CO2 treatment on the growth of Abutilon were evident early, prior to the initiation of flowering, when nitrogen availability would have been highest and pot space would not have been limited. Never- theless, the opposite was true for Amaranthus, in which significant effects of CO2 treatment on plant growth were not detectable until the final 30 d of the experiment. Elevated CO2 interacted with temperature to affect plant productivity in different ways than would have been predicted from plant responses to elevated CO2 alone. Furthermore, a majority of the interactive effects of CO2 concentration and temperature on plant growth could be interpreted in light of their effects on the rates of net leaf area production and loss, nitrogen retention, and, to a lesser degree, photosynthesis and resource partitioning.

We studied leaf area production in two annual plant species, Abutilon theophrasti and Amaranthus retroflexus, under three day/night temperature regimes (18°/14°, 28°/22°, and 38°/31°C) and two concentrations of carbon dioxide (400 and 700 @mL/L). The production of whole—plant leaf area during the first 30 d of growth was analyzed in terms of the leaf initiation rate, leaf expansion, individual leaf area, and, in Amaranthus, production of branch leaves. Temperature and CO2 influenced leaf area production through effects on the rate of development, determined by the production of nodes on the main stem (the plastochron index), and through shifts in the relationship between whole—plant leaf area and the number of main stem nodes. In Abutilon, leaf initiation rate was highest at 38°, but area of individual leaves was greatest 28°. Total leaf area was greatly reduced at 18° due to slow leaf initiation rates. Elevated CO2 concentration increased leaf initiation rate at 28°, resulting in an increase in whole—plant leaf area. In Amaranthus, leaf initiation rate increased with temperature, and was increased by elevated CO2 at 28°. Individual leaf area was greatest at 28°, and was increased by elevated CO2 at 28° but decreased at 38°. Branch leaf area displayed a similar response to CO2, but was greater at 38°. Overall, wholeplant leaf area was slightly increased at 38° relative to 28°, and elevated CO2 levels resulted in increased leaf area at 28° but decreased leaf area at 38°. The effects on leaf area closely parallel rates of biomass accumulation in the same experiment, suggesting that responses of developmental processes to elevated CO2 and interacting factors may play an important role in mediating effects on plant growth.

Alternative treatment strategies are evaluated for the postemergent herbicide Bentazon plus an oil surfactant to control cocklebur (Xanthium strumarium L.), velvetleaf (Abutilon theophrasti medikus L.), and jimson weed (Datura stramonium L.) in soybean (Glycine max (L.) Merr.]. Given an expected soybean price of $6.50/bu an expected weed-free yield of 37 bu/acre, the if-then-else' strategy of the biologist is to treat with the fixed application rate if weed density/100 sq ft is above 11 for cocklebur, 29 for velvetleaf, and 4 for jimson weed (...)