Evolutionary breakdown of distyly to homostyly is accompanied by reductions of floral scent in Primula oreodoxa

Reproductive traits that function in pollinator attraction may be reduced or lost during evolutionary transitions from outcrossing to selfing. Although floral scent plays an important role in attracting pollinators in outcrossing species, few studies have investigated associations between floral scent variation and intraspecific mating system transitions. The breakdown of distyly to homostyly represents a classic example of a shift from outcrossing to selfing and provides an opportunity to test whether floral fragrances have become reduced and/or changed in composition with increased selfing. Here, we evaluate this hypothesis by quantifying floral volatiles using gas chromatography-mass spectrometry in two distylous and four homostylous populations of Primula oreodoxa Franchet, a perennial herb from SW China. Our analysis revealed significant variation of volatile organic compounds (VOCs) among populations of P. oreodoxa. Although there was no difference in VOCs between floral morphs in distylous populations as predicted, we detected a substantial reduction in VOC emissions and the average number of scent compounds in homostylous compared with distylous populations. A total of 12 compounds, mainly monoterpenoids and sesquiterpenoids, distinguished homostylous and distylous morphs; of these, (E)-β-ocimene was the most important in contributing to the difference in volatiles, with significantly lower emissions in homostyles. Our findings support the hypothesis that the transition from outcrossing to selfing is accompanied by the loss of floral volatiles. The modification to floral fragrances in P. oreodoxa associated with mating system change might occur because high selfing rates in homostylous populations result in relaxed selection for floral attractiveness.     

COMPARISON OF PLANT DNA CONTENTS DETERMINED BY FEULGEN MICROSPECTROPHOTOMETRY AND LASER FLOW CYTOMETRY

An improved procedure is reported for determining DNA amounts of plant nuclei. Nuclei stained with propidium iodide, isolated from chopped plant leaves, were passed through an Ortho Cytofluorograph with a Lexel model 95 argon laser (514 nm) and the fluorescence measured, integrated, and recorded using an Ortho 2140 Data Acquisition computer. All nuclear samples were mixed with nuclei of Sultan barley (2C DNA content = 11.12 pg [picogram]) as an internal standard. DNA contents of ten plant species, ranging from 2C = 1.7 pg to 36.1 pg measured by flow cytometry, correlated strongly (r = 0.99, slope = + 1.00) with DNA contents determined from Feulgen-stained nuclei of the same species using microspectrophotometry. The flow cytometric procedures were sufficiently sensitive to detect differences in DNA content between inbred lines of corn and their F1 hybrids. Our results obtained with improved procedures, specifically using propidium iodide as a fluorochrome and plant nuclei instead of chicken erythrocytes as an internal standard, demonstrate that laser flow cytometry can be a precise, rapid, and reliable method for determining nuclear DNA content of plants.     

Mutations of aspartate 103 in the Hm2 receptor and alterations in receptor binding properties of muscarinic agonists

Aspartate 103 (D103) in the third transmembrane domain of the Hm2 receptor was mutated to glutamate (D103E), asparagine (D103N), or alanine (D103A). As measured by [3H]-NMS, no significant binding was observed in D103A, while a 2-fold decrease in ligand affinity was seen in D103E and a 32-fold decrease in affinity was found in the D103N mutant. Examination of reference agonists showed greater loss of affinity in D103N than in D103E with the rank order of change being: L-607,207>carbachol>arecoline>pilocarpine>oxotremorine>McN-A-343. Of the novel 1-azabicyclo[2.2.1]-heptan-3-one oxime agonists examined, arylacetylene oximes showed little alteration in binding in either the D103E or D103N mutants, while the geometric isomers of several bicyclic aryl-ene-yne oximes showed significant changes in affinity, especially in the D103N mutant. Thus, overall size of the agonist and/or spatial orientation of the molecule within the binding pocket contribute to changes measured in binding.     

Estrogen Enhances Performance of Female Rats during Acquisition of a Radial Arm Maze

Estrogen can influence the expression of behaviors not associated directly with reproduction, including learning and memory. However, the effects of estrogen on learning and memory in mammals are complex, dependent on a variety of factors. The radial arm maze is a traditional experimental task that takes advantage of the natural foraging strategy of rats and provides an appropriate measure for studying the effects of estrogen on working memory in this species. In the experiments reported here, ovariectomized rats were implanted subcutaneously with 5-mm Silastic capsules containing 25% estradiol diluted with cholesterol. Control females received 5-mm Silastic capsules containing 100% cholesterol. Results of three separate experiments demonstrated that estradiol administered by Silastic implants for 30 days prior to eight-arm radial maze training, during the 24 days of maze training, or both significantly improved working memory performance compared to females treated with cholesterol alone, as indicated by improved arm choice accuracy over trials. The positive effect of estradiol exposure prior to training suggests that estrogen may induce neuronal changes that persist beyond the period of exposure with functional consequences for behavior.     

Elemental signatures of human diets from the Georgia Bight

Multielement analysis was performed on bone samples extracted from the femora of 39 adults from three mortuary sites (Johns Mound, Santa Catalina de Guale, and Santa Catalina de Guale de Santa Meria) and time periods (late preagricultural, early contact, and late contact) in the Georgia Bight. This study was used to investigate whether elemental analysis would support or contradict other lines of data regarding diets and dietary change previously generated for the region. The data are in agreement with an earlier interpretation, based on stable isotopes, that dietary maize increases through time but fails to support the idea that marine resources decreased in importance. Rather, it appears that the wild plant food component of the diets decreases as maize increases in importance; throughout the sequence, marine resources comprise a significant portion of the diets. © 1995 Wiley-Liss, Inc.     

Velvetleaf,Abutilon theophrasti (malvaceae), history and economic impact in the United States

Velvetleaf,Abutilon theophrasti, a native of China, was originally introduced into the New World before 1750 as a potential fiber crop for the American colonies. Initial introductions may have come from England because of similar interests in the development of fiber crops. Commercial fiber production from velvetleaf was attempted by U.S. farmers for more than a century. The latest known attempts were made in the latter part of the 19th century in Illinois and New York. Velvetleaf never competed well with hemp, at least partly due to a lack of proper machinery for fiber processing. These early experimental plantings were apparently the source of velvetleaf as a weed in row crops. One velvetleaf plant is capable of producing as many as 8,000 seeds, and viability may extend beyond 50 yr. The plant is well adapted to our upper Midwest where maize (Zea mays) and soybeans (Glycine max) are the major row crops. The reservoir of velvetleaf seed in the soil is increasing. The current annual economic loss due to velvetleaf in maize and soybeans is estimated to be approximately $343 million per year.     

Influence of Sulfur Nutrition on Developmental Patterns of Some Major Pea Seed Proteins and Their mRNAs

In addition to the marked reduction in legumin synthesis and legumin mRNA levels reported earlier (Chandler, Higgins, Randall, Spencer 1983 Plant Physiol 71: 47-54), pulse labeling of S-deficient Pisum sativum L. seeds showed that a high relative level of total vicilin (vicilin plus convicilin) synthesis was maintained throughout the entire phase of protein accumulation, whereas in nondeficient seeds vicilin synthesis is largely confined to the first half of this phase. Fractionation of pulse-labeled proteins on Na-dodecylsulfate-polyacrylamide gels showed that the synthesis of the M_r 50,000 family of vicilin polypeptides was increased and greatly extended in S-deficient seeds whereas that of convicilin was slightly reduced. Other changes apparent from pulse-labeling experiments include a depression, to different degrees, in the synthesis of three major albumin polypeptides.

The level of the mRNAs for seven major seed proteins was followed throughout development of control and sulfur-deficient seeds. In all cases, the changes in each mRNA closely reflected the pattern of synthesis of its corresponding polypeptide seen by pulse labeling. S-deficient seeds showed an elevated level of M_r 50,000 vicilin mRNA which remained high throughout seed formation, whereas legumin mRNA levels were greatly reduced at all stages of development.

When S-deficient plants were given an adequate supply of sulfate midway through seed development, there was a shift toward the protein synthesis profile characteristic of healthy plants. The synthesis of legumin and two albumins rapidly increased and the synthesis of M_r 50,000 vicilin declined more slowly. Similar responses were seen in detached, S-deficient seeds supplied directly with adequate sulfate.