Biomedical subjects
W R Krul
Publications and source records attributed to W R Krul.
Physical, Chemical, Developmental, and Genetic Factors that Modulate the Agrobacterium-Vitis Interaction.
Tumor formation in Vitis species and hybrids, incited by Agrobacterium tumefaciens, was altered by chemical, physical, developmental, and genetic variables. Knowledge of the effect of these variables was used to develop a stringent in vitro assay system to select parents for a study of genetic factors that modulate tumor formation. Tumor formation was reduced by short day preconditioning of assay plants and by inoculation of the morphological apex of isolated stem segments. Pretreatment of plants with auxin or cytokinin altered specificity in various combinations of strains and host genotypes. All Vitis species and hybrids formed tumors in response to strains designated as limited host range, but some displayed a necrotic reaction (cell death at and below site of inoculation) or a null response (same as the response to inoculation with an avirulent strain) to strains designated as wide host range (VC Knauf, CG Panagopoulos, EW Nester [1982] Phytopathology 72: 1545-1549). Screens of F(1) progeny, derived from crosses of null, necrotic, and tumor-producing phenotypes, demonstrated that the null and the necrotic phenotypes were modulated by dominant and recessive host genes. The extent of cellular necrosis in the necrotic phenotype was modified by the morphological location of the inoculation site, by the presence of buds on the host stem, and by deletion of the tryptophane monooxygenase locus gene of the Ti-plasmid.
A device for comparing callus growth rates in vitro.
A device to compare the kinetics of callus growth in vitro is described. Changes in volumes of callus grown in scintillation vials were monitored photometrically without removing the sample from the solid support and medium. It is shown that a fiberglass-paper solid support is superior to a plastic foam solid support for the growth of American chestnut callus.
Nucleic Acid and protein metabolism of senescing and regenerating soybean cotyledons.
An alternative to the leaf disk system for studies of the metabolism of senescence is described. The progress of senescence of soybean (Glycine max L.) cotyledons is arrested when the epicotyl is removed. Epicotyl removal at 16 or 17 days reversed the decline in nucleic acid, protein, and chlorophyll content in the cotyledon. Epicotyl removal at 18 days did not reverse the decline in the above components, and therefore the progress of cotyledon has passed the point of no return. Cotyledons lost 90% of their nucleic acid and 80% of their protein before senescence became irreversible. The rate of recovery in various macromolecular components after epicotyl removal did not occur in an equal manner. Nucleic acid was regenerated at a faster rate than chlorophyll, which was regenerated at a faster rate than soluble protein. The heavy nucleic acid components (ribosomal and heavy ribosomal messenger fractions) regenerated at greater rates than did the soluble RNA or DNA. No label from (14)CO(2) was incorporated into DNA of the cotyledons when the epicotyl was present but label was incorporated into DNA after epicotyl removal.The parallels between the mechanisms of cotyledon senescence and apical dominance are discussed.
Polar Indole-3-acetic Acid Diffusion in Nonliving and Model Systems.
Polar indole-3-acetic acid movement was observed in killed plant segments and in artificial model systems. The polar diffusion of indole-3-acetic acid was observed in tissue killed by chemical or physical means in an agar-plant system and in a multicelled Plexiglas dialysis chamber containing hypocotyl tissue gradients or gradients of anion exchange material.It was suggested that polar indole-3-acetic acid movement in excised segments may be a reflection of the diffusion of indole-3-acetic acid through asymmetric gradients of materials with binding characteristics somewhat similar to ion exchange.
Increased root initiation in pinto bean hypocotyls with 2,4-dinitrophenol.
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