Biological Significance of Low Weed Population Densities on Sweet Corn

2010 ◽  
Vol 102 (2) ◽  
pp. 464-468 ◽  
Author(s):  
Martin M. Williams
Keyword(s):  
Sweet Corn ◽  
Biological Significance ◽  
Population Densities ◽  
Weed Population

Maize Dwarf Mosaic Can Reduce Weed Suppressive Ability of Sweet Corn

Weed Science ◽  
2012 ◽  
Vol 60 (4) ◽  
pp. 577-582 ◽  
Author(s):  
Martin M. Williams ◽  
Jerald K. Pataky
Keyword(s):  
North America ◽  
Sweet Corn ◽  
Field Studies ◽  
Viral Disease ◽  
Population Densities ◽  
Corn Hybrids ◽  
Weed Population ◽  
Proso Millet ◽  
Weed Growth ◽  
Weed Suppressive Ability

Maize dwarf mosaic (MDM) stunts corn growth, delays development, and is the most prevalent viral disease of sweet corn grown in many regions of North America and Europe. Although some weeds escape control in most sweet corn fields, the extent to which MDM influences the weed suppressive ability of the crop is unknown. Field studies were conducted over a 3-yr period to characterize the influence of variable MDM incidence in sweet corn on growth, fecundity, and germinability of wild-proso millet, a common weed in the crop. Treatments included five levels of MDM incidence (0, 25, 50, 75, and 100% of plants infected) in two MDM-susceptible hybrids differing in weed suppressive ability. Previous research showed that hybrid ‘Legacy’ had greater weed suppressive ability than ‘Sugar Buns’. Wild-proso millet biomass and fecundity depended largely on the hybrid in which the weed was growing. Wild-proso millet growing in Sugar Buns weighed 45 to 117% more than wild-proso millet in Legacy. Incidence of MDM in sweet corn affected wild-proso millet biomass and fecundity, but only under high weed population densities. When wild-proso millet was observed at 122 plants m−2, weed biomass increased 9 g m−2 for each additional 10% incidence of MDM of sweet corn. Weed suppressive ability of the competitive and less competitive hybrids were influenced to the same extent by MDM. Coupled with a lack of resistance to MDM in two-thirds of commercial sweet corn hybrids, the disease could be an additional factor perpetuating weed growth and fecundity in sweet corn, particularly in fields with high population densities of wild-proso millet.

Variation in Wild Proso Millet (Panicum miliaceum) Fecundity in Sweet Corn Has Residual Effects in Snap Bean

Weed Science ◽  
2007 ◽  
Vol 55 (5) ◽  
pp. 502-507 ◽  
Author(s):  
Adam S. Davis ◽  
Martin M. Williams
Keyword(s):  
Life Cycle ◽  
Population Density ◽  
Crop Yield ◽  
Weed Management ◽  
Sweet Corn ◽  
Seedling Recruitment ◽  
Residual Effects ◽  
Snap Bean ◽  
Weed Population ◽  
Proso Millet

Bioeconomic models are predicated upon the relationship between weed fecundity and crop yield loss in consecutive growing seasons, yet this phenomenon has received few empirical tests. Residual effects of wild proso millet (WPM) fecundity in sweet corn upon WPM seedling recruitment, weed management efficacy, and crop yield within a subsequent snap bean crop were investigated with field experiments in Urbana, IL, in 2005 and 2006. WPM fecundity in sweet corn showed strong positive associations with WPM seedbank density, seedling recruitment, and demographic transitions within snap bean. A negative exponential relationship between WPM initial seedling density and seedling survival of a single rotary hoe pass indicated that the rotary hoe was ineffective at low weed population densities, but its efficacy increased with increasing weed population density to a maximum of 75% seedling mortality. Efficacy of postemergent chemical control of WPM was unaffected by WPM population density. Path analysis models demonstrated dependence between WPM fecundity in sweet corn, WPM seedling recruitment in snap bean, and reductions in snap bean yield in subsequent growing season, mediated by negative impacts of WPM seedling establishment on snap bean stand. These results underscore the importance of expanding integrated weed management programs to include management of annual weed populations both at the end of their life cycle, by reducing fecundity and seed survival, and at the very beginning of their life cycle, by reducing seedling recruitment and establishment.

Interference of Palmer amaranth (Amaranthus palmeri) Density in Grafted and Nongrafted Watermelon

Weed Science ◽  
2018 ◽  
Vol 67 (2) ◽  
pp. 229-238 ◽  
Author(s):  
Matthew B. Bertucci ◽  
Katherine M. Jennings ◽  
David W. Monks ◽  
Jonathan R. Schultheis ◽  
Frank J. Louws ◽  
...  
Keyword(s):  
Competitive Ability ◽  
Field Experiments ◽  
Citrullus Lanatus ◽  
Hollow Heart ◽  
Palmer Amaranth ◽  
Yield Reduction ◽  
Amaranthus Palmeri ◽  
Population Densities ◽  
Weed Population ◽  
Fruit Number

AbstractWatermelon [Citrullus lanatus(Thunb.) Matsum & Nakai] grafting is commonly used for management of diseases caused by soilborne pathogens; however, little research exists describing the effect of grafting on the weed-competitive ability of watermelon. Field experiments determined the response in yield, fruit number, and fruit quality of grafted and nongrafted watermelon exposed to increasing densities of Palmer amaranth (Amaranthus palmeriS. Watson). Grafting treatments included ‘Exclamation’ triploid (seedless) watermelon grafted on two interspecific hybrid squash rootstocks ‘Carnivor’ and ‘Kazako’, with nongrafted Exclamation as the control. Weed treatments includedA. palmeriat densities of 1, 2, 3, and 4A. palmeriplants per watermelon planting hole (0.76-m row) and a weed-free control. IncreasingA. palmeridensities caused significant reductions (P <0.05) in marketable watermelon yield and marketable fruit number. Watermelon yield reduction was described by a rectangular hyperbola model, and 4A. palmeriplants planting hole−1reduced marketable yield 41%, 38%, and 65% for Exclamation, Carnivor, and Kazako, respectively. Neither grafting treatment norA. palmeridensity had a biologically meaningful effect on soluble solids content or on the incidence of hollow heart in watermelon fruit.Amaranthus palmeriseed and biomass production was similar across weed population densities, but seed number per femaleA. palmeridecreased according to a two-parameter exponential decay equation. Thus, increasing weed population densities resulted in increased intraspecific competition amongA. palmeriplants. While grafting may offer benefits for disease resistance, no benefits regarding weed-competitive ability were observed, and a consistent yield penalty was associated with grafting, even in weed-free treatments.

Biodynamic preparations: Short-term effects on crops, soils, and weed populations

2000 ◽  
Vol 15 (3) ◽  
pp. 110-118 ◽  
Author(s):  
Lynne Carpenter-Boggs ◽  
John P. Reganold ◽  
Ann C. Kennedy
Keyword(s):  
Soil Fertility ◽  
Crop Yields ◽  
Plant Biomass ◽  
Biological Significance ◽  
Mineral Fertilizer ◽  
Growth And Yield ◽  
Short Term ◽  
Npk Fertilizers ◽  
Weed Population ◽  
Biodynamic Preparations

AbstractBiodynamic agriculture is an organic farming system that utilizes fermented herbal and mineral preparations as compost additives and field sprays. This study was conducted to determine whether biodynamic preparations affect lentil and wheat growth and yield, soil fertility, or weed populations in the short run. Each of four nutrient treatments, biodynamically prepared compost, non-biodynamic compost, mineral NPK fertilizer, and no fertilizer, were tested with and without biodynamic field sprays. Crop yield, crop quality, and soil fertility were similar in plots treated with mineral NPK fertilizers, biodynamic compost, or non-biodynamic compost. Use of compost raised soil pH from 6.0 without compost to 6.5 with compost. Compost application reduced the broadleaf weed population by 29% and reduced the grass weed population by 78%. Biodynamic sprays altered soil and grain N chemistry, but the effects are of unknown biological significance. Use of the biodynamic field sprays correlated with higher yield of lentil per unit plant biomass, lower grain C and crude protein contents, greater content in soft white spring wheat, and greater content in soil. In general, soils and crops treated with biodynamic preparations showed few differences from those not treated. Application of composts with or without the preparations produced similar crop yields with lower weed pressure, compared with equal nutrients supplied by mineral fertilizer, but any additional short-term benefits from biodynamic preparations remain questionable.

scholarly journals Effects of Cover Crops, Nitrogen, and Tillage on Sweet Corn

2002 ◽  
Vol 12 (1) ◽  
pp. 118-125 ◽  
Author(s):  
Gary R. Cline ◽  
Anthony F. Silvernail
Keyword(s):  
Cover Crops ◽  
Sweet Corn ◽  
Winter Rye ◽  
No Tillage ◽  
Population Densities ◽  
Inorganic N ◽  
N Content ◽  
Foliar N ◽  
Winter Cover ◽  
Winter Cover Crops

Effects of tillage, inorganic N, and winter cover crops on sweet corn (Zea mays) were examined in 1994, 1995, and 1996. Tillage treatments were tillage or no tillage, and N treatments were the addition of inorganic N at 0 (N0) or 200 (N+) kg·ha-1 (0 or 179 lb/acre). Winter cover crops included hairy vetch (Vicia villosa), winter rye (Secale cereale), and a vetch/rye biculture. In the N0, rye treatment, the soil was N deficient in 1994 and highly N deficient in 1995 and 1996. When vetch shoot N content was ≥150 kg·ha-1 (134 lb/acre) (1994 and 1995), addition of inorganic N did not increase corn yields, and it only increased corn foliar N concentrations by 8%. Reductions in corn yields (29%) and foliar N concentrations (24%) occurred when vetch shoot N content was only 120 kg·ha-1 (107 lb/acre) (1996) and inorganic N was not supplied. In 1994, the vetch/rye biculture supplied sufficient N for maximum corn yields, but addition of inorganic N increased yields by more than 50% in 1995 and 1996. Under tilled conditions, the vetch N contribution to corn appeared to equal (1996) or exceed (1994 and 1995) 82 kg·ha-1 (73 lb/acre) of N supplied as ammonium nitrate, whereas a mean value of 30 kg·ha-1 (27 lb/acre) was obtained for the biculture cover crop (1995 and 1996). No significant effects of tillage on sweet corn population densities were detected following vetch, but no-tillage significantly reduced corn population densities following rye (17%) or biculture (35%) cover crops compared to tillage. No-tillage did not reduce yields from emerged seedlings (per plant basis) for any cover crops. Vetch appeared to be a satisfactory N source for sweet corn when vetch N content was ≥150 kg·ha-1, and it could be used with no-tillage without yield reductions.

Microstructural morphology of sphingolipid dispersions as investigated by freeze-fracture EM

1995 ◽  
Vol 53 ◽  
pp. 944-945
Author(s):  
Vitthal S. Kulkarni ◽  
Wayne H. Anderson ◽  
Rhoderick E. Brown
Keyword(s):  
Acyl Chain ◽  
Biological Significance ◽  
Freeze Fracture ◽  
Fatty Acyl ◽  
Fatty Acyl Moiety ◽  
Aqueous Dispersions ◽  
Head Groups ◽  
Lipid Species ◽  
Microstructural Morphology ◽  
Layer Chromatography

The biological significance of the sphingomyelins (SM) and monoglycosylated sphingolipids like galactosylceramides (GalCer) are well documented Our recent investigation showed tubular bilayers in the aqueous dispersions of N-nervonoyl GalCer [N-(24:lΔ15,cls) GalCer] (a major fatty acyl moiety of natural GalCer). To determine the influence of lipid head groups on the resulting mesophasic morphology, we investigated microstructural self-assemblies of N-nervonoyl-SM [N-(24:1 Δ15,cls) SM; the second most abundant sphingomyelin in mammalian cell membranes], 1- palmitoyl-2-nervonoyl phosphatidylcholine [PNPC] (the lipid species with the same acyl chain configuration as in N-(24: 1) GalCer) and also compared it with egg-SM by freeze-fracture EM.Procedures for synthesizing and purifying N-(24:1) GalCer, N-(24:1) SM, and PNPC have been reported . Egg-SM was purchased from Avanti Polar Lipids, Alabaster AL. All lipids were >99% pure as checked by thin layer chromatography. Lipid dispersions were prepared by hydrating dry lipid with phosphate buffer (pH 6.6) at 80-90°C (3-5 min), vigorously vortexing (1 min) and repeating this procedure for three times prior to three freeze-thaw cycles.

Ultrastructural Localization Study of Carcinoembryonic Antigen (CEA) in Gastric Cancer: Immunoelectron Microscopic Observation

1990 ◽  
Vol 48 (3) ◽  
pp. 252-253
Author(s):  
Dong Yuming ◽  
Yang Guanglin ◽  
Wu Jifeng ◽  
Chen Xiaolin
Keyword(s):  
Gastric Cancer ◽  
Intestinal Metaplasia ◽  
Cancer Cells ◽  
Microscopic Observation ◽  
Biological Significance ◽  
Ultrastructural Localization ◽  
Mucinous Carcinoma ◽  
Surface Glycoprotein ◽  
Tubular Adenocarcinoma ◽  
Pap Method

On the basis of light microscopic observation, the ultrastructural localization of CEA in gastric cancer was studied by immunoelectron microscopic technique. The distribution of CEA in gastric cancer and its biological significance and the mechanism of abnormal distribution of CEA were further discussed.Among 104 surgically resected specimens of gastric cancer with PAP method at light microscopic level, the incidence of CEA(+) was 85.58%. All of mucinous carcinoma exhibited CEA(+). In tubular adenocarcinoma the incidence of CEA(+) showed a tendency to rising with the increase of degree of differentiation. In normal epithelia and intestinal metaplasia CEA was faintly present and was found only in the luminal surface. The CEA staining patterns in cancer cells were of three types--- cytoplasmic, membranous and weak reactive type. The ultrastructural localization of CEA in 14 cases of gastric cancer was studied by immunoelectron microscopic technique.There was a little or no CEA in the microvilli of normal epithelia. In intestinal metaplasia CEA was found on the microvilli of absorptive cells and among the mucus particles of goblet cells. In gastric cancer CEA was also distributed on the lateral and basal surface or even over the entire surface of cancer cells and lost their polarity completely. Many studies had proved that the alterations in surface glycoprotein were characteristic changes of tumor cells. The antigenic determinant of CEA was glycoprotein, so the alterations of tumor-associated surface glycoprotein opened up a new way for the diagnosis of tumors.

RIBONUCLEOPROTEIN PARTICLES CONTAINING mRNA and pre-mRNA

1973 ◽  
Vol 74 (Suppl) ◽  
pp. S130-S167 ◽  
Author(s):  
O. P. Samarina ◽  
E. M. Lukanidin ◽  
G. P. Georgiev
Keyword(s):  
Structural Organization ◽  
General Scheme ◽  
Biological Significance ◽  
Mrna Transport ◽  
Ribonucleoprotein Particles ◽  
Mrna Precursor

ABSTRACT This paper is a review of the data concerning the nature, structural organization, properties and biological significance of the particles, containing mRNA and pre-mRNA (precursor of mRNA), i. e., (1) nuclear pre-mRNA-containing particles (2) free cytoplasmic mRNP (ribonucleoproteins), or informosomes (3) polysome-bound mRNP. Some new data on the comparison of nuclear and cytoplasmic particles, the nature of poly A-containing structures, involvement of informofers in Adenovirusspecific RNA transfer are presented. The general scheme of mRNA transport from nucleus to cytoplasm is discussed.

Sign in / Sign up

Export Citation Format

Share Document