Peter M. Bradley

Some effects of plant growth regulators on tissue cultures of the marine red alga Agardhiella subulata (Gigartinales, Rhodophyta)

We examined whether auxins and cytokinins, either singly or in combination, stimulate cell division in tissue cultures of a red seaweed. Our experimental model consisted of filamentous and callus-like growths that developed from cross-sectional discs cut from young branches of Agardhiella subulata. Plant growth regulators were added to the medium to give combinations of an auxin with a cytokinin over a range of concentrations (1 µg L−1 −10 mg L−1). Several mixtures of auxins and cytokinins, as well as some single auxins, cytokinins and phenolics, stimulated cell division and growth in the tissue cultures beyond that of controls. The treatments that were effective included: phenylacetic acid/zeatin; phenylacetic acid/6-benzylaminopurine; α-naphthaleneacetic acid/zeatin; 2,4,5-trichlorophenoxyacetic acid/6-benzylaminopurine; and indoleacetic acid/kinetin. High concentrations of cytokinins (i.e. 10 mg L−1) inhibited the regeneration of plants in some of the cell cultures. These results provide further evidence that growth regulators can be used for the tissue culture of seaweeds and for the study of developmental phenomena in these plants.

Carrageenan analysis of tissue cultures and whole plants of Agardhiella subulata

For the past several years, our laboratory has been involved in developing basic protoplast and tissue culture techniques for carrageenan- and agar-producing seaweeds which can potentially be used for strain improvement. Both types of techniques offer new opportunities for genetic improvement in seaweeds not available using classical plant breeding methods (Cheney, 1986). While protoplast and tissue culture techniques are well developed and widely applied to higher plants today for crop improvement, their application to seaweeds is just beginning.

Polyamines and arginine affect somatic embryogenesis of Daucus carota

Summary Cell suspension cells of Daucus carota were treated with putrescine (0.03 μ M) in the presence of 2 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) and 40 mg/l arginine. When the cultures were transferred to a medium lacking 2,4-D and putrescine, globular embryos were produced which did not develop further. Globular embryos were subsequently transferred to a medium lacking arginine, and rapid synchronous development of the embryos occurred. This approach offers the possibility of controlling the process of somatic embryogenesis for developmental and biochemical studies, as well as the opportunity for large scale synchronous production for propagation purposes.

Production of enucleated plant protoplasts of Allium cepa

Abstract Protoplasts were isolated enzymatically from epidermis of Allium cepa bulbs. Some of the protoplasts separated into nucleated and enucleated portions of similar size.

One step antibiotic disk method for obtaining axenic cultures of multicellular marine algae

A simple and rapid method for obtaining axenic plant material has been devised where antibiotic-containing paper disks are applied to nutrient agarose or agar plates upon which small pieces of plant have been spread. By applying multiple disks to the agarose plate, susceptibility to a large number of antibiotics can be tested simultaneously. Clear zones are produced around those disks where contaminating bacteria are susceptible. Plant pieces are then removed from the clear zones and separately tested for sterility to identify the axenic pieces. The method has been successfully applied to multicellular marine algae (e.g.Enteromorpha, Porphyra, laminaria, Gracilaria andAgardhiella). Pieces fromAgardhiella plants survive better on nutrient medium solidified with agarose when α-naphthaleneacetic acid and zeatin are present in the medium.

The production of higher plant subprotoplasts

ConclusionsThere are several examples in the literature to show that the formation of subprotoplasts is favored by conditions of high osmoticum concentrations and the presence of elongated cells. As plant tissues are plasmolysed, some of the elongated cells will fragment into two or more parts. When the cell wall is removed with enzymes, the subprotoplasts are released into the medium. If elongated cells are not present, centrifugation or budding of protoplasts can be used, or large fragile cells can be obtained by a high auxin treatment. Each method gives mixed populations of subprotoplasts with protoplasts. Purified fractions are obtained by density gradient centrifugation, or by picking with a micropipet.

Uptake of cyanobacteria contained in oil drops by plant protoplasts

Den Verlauf der SN-Reaktionen untersuchten wir in Abh/ingigkeit yon Temperatur und Zeit (Fig. 1). Die Eintauschkapazit/it des Na-Bentonits wurde zu 66,5 mMol Kationen/100 g lufttrockenem Na-Bentonit bestimmt [4]. Da aus 100 g lufttrockenem Bentonit nach Eintausch und Vakuumtrocknung (130 ~ 0,05 Torr, Gewichtskonstanz) 93,4 g S-Benzyl-tetrahydrothiophenium-Bentonit erhalten werden, verffigt der zur Reaktion eingesetzte Bentonit fiber einen SulfoniumIonengehalt von 71,2 mMol/100 g.

Natural Antibiotic Resistance of Bacteria Isolated from a Peat Bog at Poutwater Pond, Holden, Massachusetts

Abstract. Plant material has accumulated in the Poutwater Pond peat bog for thousands of years. The area has acid conditions and a thick (5 meter) accumulation of slowly decomposing plant material. The nature of the microbes living at different depths in this environment is not well known. Bacteria were isolated from a core collected at the peat bog and brought in to the laboratory. Samples from different depths were cultured on trypticase soy agar. A streak plate method was used to isolate some colonies of bacteria. The BIOLOG™ technique used for microbial community analysis showed that the assemblage of microorganisms remains similar at different depths of the peat bog. Gram staining showed that both Gram negative and Gram positive rods were cultured from different depths of the peat bog. The BIOLOG™ identification system was used to identify four of the bacteria as Pseudomonas chlororaphis, P. fluorescens, Bacillus mycoides and Alcaligenes denitrificans. Some bacteria have been tested for antibiotic susceptibility. Bacteria demonstrating antibiotic resistance occur at different depths of the peat bog. The results of this study are useful in understanding the organisms that live under these conditions.

The Effects of Putrescine on Somatic Embryogenesis of Daucus Carota as Examined by Two-Dimensional Electrophoresis

Plant developmental processes can be studied using tissue culture models, e. g., the production of somatic embryos using cell suspension cultures. In this study, a putrescine/arginine treatment was used to synchronize the embryogenic process, and two-dimensional electrophoresis was used to compare the translational profiles at different stages of embryo formation [P.M. Bradley (1984) Ph.D. Thesis, Worcester Polytechnic Institute].