Barbara D. Webster

THE STIGMATIC EXUDATE OF PHASEOLUS VULGARIS L.

Stigmatic exudate of Phaseolus vulgaris L. includes lipids, amino acids, protein, reducing acids, phenols, and sugar. Alkaloids are not present. In addition to its primary role in retention and germination of its pollen, the exudate may function as a nutritive source for floral visitors, including thrips and bees, and as a protectant against desiccation of the stigma and against invasion by undesirable insects or spores.

In dry pear (Pyrus communis L.) pollen, membranes assume a tightly packed multilamellate aspect that disappears rapidly upon hydration

SummaryUltrastructural details of dry (7% moisture content) and hydratedPyrus communis L. pollen are revealed following freezesubstitution preparation for electron microscopy. Dry pollen is characterized by tightly packed, multilamellate membranous profiles found in association with plasma membrane, vesicles, ER, dictyosomes and some double-membrane bound organelles. Dry pollen also shows unit-membrane bound, densely osmiophilic bodies often with tightly packed multilamellations contained within and, at times, in their bounding membranes. These features are not evident in hydrated pollen. Results suggest that multilamellate membranes form as the plasma membrane, vesicles, ER, and double-membrane bound organelles undergo dehydration, and that upon hydration they rapidly resume normal unilamellate structure.

Control of Acanthoscelides obtectus Say (Coleoptera: Bruchidae) in Phaseolus vulgaris L. seed stored on small farms—I. Evaluation of damage

Abstract On-farm experiments were carried out in Darien (Valle de Cauca), Colombia, South America on stored beans (Phaseolus vulgaris L.) to evaluate the effectiveness of post-harvest treatments designed for the control of Acanthoscelides obtectus Say and adoptability by small farmers. Three treatments effectively reduced A. obtectus damage below the economic threshold (4% damaged grains) determined in this study. Vegetable oil (5 ml/kg) reduced emergence and prevented reproduction of bruchids for 8 months after harvest. Kitchen ash (20% by weight) controlled bruchid reproduction throughout the 39-week storage period. Black pepper controlled reproduction under heavy artificial bruchid infestation. The potential for small-farmer adoption of these and less successful treatments is evaluated.

Leaf and Inflorescence Abscission in Olive. I. Regulation by Ethylene and Ethephon

Abscission responses of explants of reproductive olive shoots differ depending on sources of ethylene that elicit the response (applied ethylene or ethylene evolved from ethephon breakdown), organ type, developmental stage of the inflorescence, and site of the potential abscission zone. Disparities in response result from dissimilarity in sensitivity between leaves and inflorescences and among same organs of differing maturities, and possibly from quantitative differences in amount of ethylene at an abscission zone. In addition to peduncular abscission, abscission occurs at numerous sites within the inflorescence with ethylene treatment but not with ethephon.

FLOWERING AND FRUITING PATTERNS OF PHASEOLUS VULGARIS L.

Spatial and temporal aspects of reproductive development were examined in morphological units-a compound raceme and subtending axillary flowers and trifoliolate leaf-of Phaseolus vulgaris. Flowering occurs acropetally, and the probability of flowering varies with the position of a bud in a unit: axillary, basal buds have a higher percentage of flowering than more distal buds on a raceme. The percentage of bud and fruit abortion also varies in relation to position within a unit. The axillary, basal buds are the first to flower and have the lowest percentage of abortion. All distal buds abort. Nonflowering buds abort in the green-bud stage of floral ontogeny. Growth and cytological analyses indicate that the aborting fruits contain embryos in the proembryo and early and late globular stages of embryogeny. The percentage of abortion at each stage varies with the position of the fruit within a unit. Axillary and basal fruits contain embryos in the late globular stage. Distal fruits contain embryos in the proembryo stage. Fruits with embryos in the early globular stage are in the midregion of the raceme. Abortion-inducing factors appear to be important in the green-bud stage of ontogeny and in early stages of fruit/embryo development.

Morphogenesis of Effective and Ineffective Root Nodules in Phaseolus vulgaris L.

Seedlings of Phaseolus vulgaris, inoculated with an effective strain of Rhizobium phaseoli (CIAT 73) or an ineffective strain (14c), were maintained on an N-free nutrient solution in sterilized sand. Acetylene reduction was measured periodically, and nodules were harvested for light and electron microscopy. In plant host cells infected with CIAT 73, there was an increase in cell volume, nuclear size, and mitochondrial length as bacteria multiplied and became bacteroidal. Golgi activity and rough endoplasmic reticulum (RER) were sparse at nodule maturity, but close associations of amyloplasts and elongated, energized mitochondria were observed. Nitrogen fixation peaked at 5 wk and dropped sharply coincident with flowering. Plant host cells infected with 14c typically contained numerous mitochondria; Golgi bodies and RER were conspicuous throughout nodule development. By the time the bacteria became bacteroidal, plant shoots were chlorotic, and under nitrogen stress the apex had made the transition to flowering. Data suggest that such ineffective nodulation may accelerate the process of normal nodule senescence.

Inflorescence Abscission in Olive: Anatomy and Histochemistry in Response to Ethylene and Ethephon

Naturally occurring postanthesis abscission in olive (Olea europaea L. Manzanillo) results in approximately 99% loss of flowers. Ethylene gas treatment induces sequential abscission of flowers, rachis branches and internodal sections, and peduncles of mature (expanded) inflorescences on shoot explants. Treatment with 2-chloroethyl phosphonic acid (ethephon) triggers sequential abscission of flowers and peduncles of mature inflorescences but only very infrequently rachises and never internodal sections. Immature (not fully expanded) inflorescences on shoot explants abscise intact in response to ethylene gas or ethephon. Sites of floral abscission on trees are limited to bracts, petals, individual flowers, and peduncles. With the exception of bracts, floral organs on trees do not abscise until after pollination. Naturally occurring abscission is preceded by plasmolysis of abscission zone cells, loss of cell wall materials as evidenced by changes in stain intensity, and lacunar cell separation. Abscission of floral organs of trees and of explants treated with ethephon or ethylene gas occurs at localized sites and is preceded by cell wall gelatinization and swelling (in ethephon-treated samples only), loss of cell wall and middle lamella pectins, lacunar cell separation, and senescence of cortical parenchyma cells. Phytotoxic symptoms, plasmolysis and cell senescence throughout all explant tissues occurred with ethephon treatments. All active abscission zone cells exhibit small size, isodiametric shape, dense cytoplasm, and starch accumulation. Cell division does not occur in any abscission zone with any treatment.

Seed Abortion in Phaseolus vulgaris L.

The earliest abortion-related changes seen in seeds of Phaseolus vulgaris occur in maternal tissue. Starch is depleted rapidly, integumentary and nucellar cells become vacuolate, and walls of cells in the middle layers of the outer integument are distorted. These changes are followed by cessation of embryo growth. Seeds of fruits in the distal region of the raceme show signs of abortion 1 d after anthesis; those in the midregion exhibit abortion-related changes 2 d post-anthesis, and those in axillary or basal positions, 3 d post-anthesis. Seeds of nonaborting axillary and basal fruits show significant developmental changes 4 d after anthesis. Such changes may result in the diversion of assimilates from distal fruits to axillary or basal seeds/fruits. This subsequently may induce abortion of distal seeds/fruits at different developmental stages.

Spatial congruence between exine pattern, microtubules and endomembranes in Vigna pollen

The role of microtubules and endomembranes in pollen wall pattern formation in Vigna vexillata L. was examined using fluorescence laser scanning confocal microscopy. Indirect immunofluorescence using anti-β-tubulin antibodies revealed that the arrangement of the cortical microtubular cytoskeleton in microspores resembled the reciprocal of the reticulate ektexine ornamentations of mature V. vexillata pollen. Patches of microtubules in cortical cytoplasm corresponded in location with the lumina of the exine reticulum and with apertural sites. Microtubules were absent from cytoplasm under muri (ridges) of the exine reticulum. Labeling of microspores during the mid-tetrad stage with the endomembrane-specific fluorochrome DiOC6 produced a pattern similar to that of the microtubules; i.e., DiOC6 staining was localized in cytoplasm underlying lumina and absent from cortical cytoplasm underlying sites of muri. This report represents the first observation of congruence of the pattern of occurrence of any subcellular organelles with exine pattern and, in particular, the congruence of both microtubules and endomembranes in cortical cytoplasm with the lumina of the reticulate exine.

Control of Acanthoscelides obtectus Say (Coleoptera : Bruchidae) in Phaseolus vulgaris L. seed stored on small farms. II: Germination and cooking time

Abstract Treatments which successfully controlled bruchids in on-farm experiments were evaluated to determine effects on seed quality and cooking time. Relative cooling time was determined by cooking beans to the half-cooked point in a modified Mattson cooker. Germination was determined by trials planted in sand, and seedling vigor was estimated by dry weight of 8-day old seedlings. Cooking time, germination, and seedling vigor were not significantly changed by storage treatment with vegetable oil, threshing residues, kitchen ash, Malathion and black pepper. Analysis of bruchid damage on seed quality showed a decline in germination and seedling vigor related to the number of emergence holes.