Intermediary carbon metabolism of Azospirillum brasilense.

Azospirillum brasilense Sp 7 grew rapidly in AZO medium containing reduced nitrogen and succinate as an energy source, with a doubling time of 43 min. No growth was measured with glucose as the sole carbon source. In contrast, Azospirillum lipoferum Sp 59b could grow in media containing either succinate or glucose with a doubling time of 69 min and 223 min, respectively. Warburg-Barcroft respirometry showed that the rate of oxygen consumption by A. brasilense Sp 7 on glucose medium (0.034 mumol of O2 min-1 mg-1 of cell protein) was only one-quarter of that on succinate medium (0.14 mumol of O2 min-1 mg-1). Radioisotopic labeling showed that very little glucose was assimilated by A. brasilense Sp 7 as compared to succinate. High respiration rates were measured on A. lipoferum Sp 59b with either succinate (0.15 mumol of O2 min-1 mg-1) or glucose (0.13 mumol of O2 min-1 mg-1) as the sole carbon source. The pattern of CO2 evolution from differentially labeled succinate indicated that A. brasilense Sp 7 had a complete tricarboxylic acid cycle. Assimilation of most of the radioactivity from labeled succinate, pyruvate, and acetate into lipids suggested a strong anabolic metabolism and the presence of an active malic enzyme of phosphoenolpyruvate carboxykinase. The distribution of radioactivity from differentially labeled pyruvate showed that gluconeogenesis competed with pyruvate dehydrogenase. Uptake and incorporation of labeled acetate also indicated the presence of a glyoxylate cycle in A. brasilense Sp 7.

Single gene mutations in tomato plants regenerated from tissue culture.

Plants were regenerated from cultured leaf explants of an inbred variety of Lycopersicon esculentum. Seeds were collected from the regenerated plants and sown in the greenhouse. The resultant plants were then evaluated in the field. Several monogenic mutations segregated in the progeny of regenerated plants. The recovery of single gene mutations is evidence that plant tissue culture can be mutagenic. Complementation tests revealed that one mutation was located on the long arm of chromosome 10.

The use of nurse culture in the development of haploid clones in tomato.

A nurse culture procedure and an appropriate medium are described for obtaining vigorous haploid clones originating from single tomato pollen grains. The grains are plated on filter-paper disks mounted over intact anthers placed on a modified Murashige and Skoog medium. The plating efficiencies of such pollen cells ranges between 0 and 60%. The variability in the plating efficiencies and the potential use of this technique over that of anther culture are discussed.

Physiological Comparisons of Pith Callus With Crown-Gall and Genetic Tumors of Nicotiana glauca, N. langsdorffii, and N. glauca-langsdorffii Grown in Vitro. I. Tumor Induction and Proliferation.

Agrobacterium tumefaciens B-6 and T-37 strains, inoculated into Nicotiana glauca, N. langsdorffii, and their interspecific hybrid, which forms genetic (spontaneous) tumors as well, initiate amorphous tumors from the B-6 strain and organoid tumors (aberrant roots, stems, and buds) from the T-37 strain. In the hybrid, the critical point was to induce crown gall tumors at the site of wounding and not spontaneous genetic tumors. To succeed, this inoculation had to be made at a very early (5-6 leaf stage of development). It is observed that genetic organoid tumors readily formed at the nodes following flowering or leaf abscission. Furthermore, it was noted that genetic tumor derivatives are obtainable from hybrid pith callus or hybrid seedlings cultured in vitro.A marked difference in stem elongation was observed in hybrid tobacco plants inoculated with different strains of Agrobacterium tumefaciens or distilled water, and uninoculated controls. Inoculation of hybrid plants with the B-6-G2 avirulent strain of Agrobacterium tumefaciens stimulated stem elongation over controls, the T-37 inoculated stems were slightly stunted, and the B-6 inoculated stems were quite stunted and succumbed at an early age.

Physiological Comparisons of Pith Callus With Crown-Gall and Genetic Tumors of Nicotiana glauca, N. langsdorffii, and N. glauca-langsdorffii Grown in Vitro. II. Nutritional Physiology.

Explants of genetic tumors, tumors initiated by Agrobacterium tumefaciens strains B-6 and T-37, and excised pith plugs from Nicotiana glauca, N. langsdorffii, and N. glauca-langsdorffii were cultured on Murashige and Skoog medium. All cultures, pith callus and tumors with the exception of N. langsdorffii pith grew on this medium. Addition of glutamine to the medium resulted in highly organoid growth in N. langsdorffii pith. In order to have material comparable to other pith cultures, N. langsdorffii was initiated on 2,4-dichlorophenoxyacetic acid medium, after which it grows on complete medium as amorphous pith callus. Except for the initiation of N. langsdorffii (and N. glauca) pith, the 2,4-dichlorophenoxyacetic acid medium, caused bleaching in cultures of T-37 induced tumors and death of B-6 induced tumors. Tumor cultures, except for the seedling tumor, grew well on a minimal medium lacking kinetin, indoleacetic acid, vitamins, glycine, and inositol. Glycine was necessary only in the growth of N. langsdorffii pith callus. A tissue culture model is presented which permits comparison of the various tissue types.