The effects of calcium ions on lysine transport Into cultured Wisconsin-38 tobacco cells were examined. In the presence of calcium, lysine was transported at a relatively low rate for 30 to 40 minutes followed by a period of increasing rates and subsequent st tion at a higher rate after 2 to 3 hours. In the absence of calcium, transport was uniformly low.

No abstract

Dihydrodipicolinic acid reductase, an enzyme which catalyzes the pyridine nucleotide-linked reduction of dihydrodipicolinic acid to tetrahydrodipicolinic acid in the biosynthetic pathway leading to L-lysine, has been partially purified from maize (Zea mays cv Pioneer 3145) kernels. The crude maize extract and the partially purified enzyme were assayed for dihydrodipicolinic acid reductase by their ability to restore the capability of crude extracts of a mutant Escherichia coli (CGSC 4549; defective in dihydrodipicolinic acid reductase) to synthesize diaminopimelic acid from aspartic acid and pyruvic acid.

Incorporating activated charcoal (AC) in culture media has been shown to affect growth and development of various organisms. Since AC stimulates the development of tobacco haploid plantlets from cultured anthers, research was conducted to determine the effect of activated charcoal on pith-derived callus growth and shoot development in Nicotiana tabacum cv. Wisconsin 38. Our results indicate that the hormones required for callues growth and shoot development in Wisconsin-38 tobacco are adsorbed by AC, thereby inhibiting callus growth and prohibiting shoot development. This effect was observed even when AC was removed from the medium by filtration prior to culturing the callus.

Callus was induced in different somatic organs of Oryza sativa L. Specific minimum 2,4‐dichlorophenoxyacetic acid (2,4‐D) concentrations in the medium were necessary for the induction of callus from different organs while high levels of 2,4‐D (6–10 mg/l) induced callus formation in each organ tested. The optimum 2,4‐D concentration for callus induction and growth for root‐derived calli was 2 mg/l and for leaf‐derived 6 mg/l. Root and shoot organogenesis were induced in both root‐ and leaf‐derived calli by sub‐culturing to a medium lacking 2,4‐D. Root organogenesis occurred at a higher frequency than shoot organogenesis. Shoot organogenesis rarely occurred in calli without differentiated roots. Increased age of callus cultures almost completely inhibited shoot development. The addition of the cytokinin 6‐γ,γ‐dimethylallyl‐amino purine partially restored the potential for shoot organogenesis. Whole plants were easily recovered from the calli and grown to maturity with some plants exhibiting phenotypic abnormalities.