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The effect of light spectral quality on the growth of in vitro nodal cuttings of potato (Solanum tuberosum L.) cultivars Norland, Superior, Kennebec, and Denali were examined. The different light spectra were provided by Vita-Lite fluorescent (VF) (a white light control), blue fluorescent (BF), red fluorescent (RF), low-pressure sodium (LPS), and a combination of low-pressure sodium plus cool-white fluorescent lamps (LPS/CWF). For all cultivars, stem lengths after 4 wk were longest under LPS, followed by RF, LPS/CWF, VF, and BF (in descending order). Microscopic studies revealed that cells were shortest when cultured in BF or VF environments, and were longest in RF or LPS lamp environments. The highest number of axillary branches occurred on plantlets grown with LPS or LPS/CWF, whereas the lowest number occurred with BF. No leaf or stem edema (callus or gall-like growths) occurred with LPS or LPS/CWF lighting, and no edema occurred on cv. Norland plantlets, regardless of lighting. Results suggest that shoot morphologic development of in vitro grown potato plants can be controlled by controlling irradiant spectral quality.

Callus cultures were initiated from apical meristem explants of one to fourweek-old aseptically-grown barley (Hordeum vulgare L. cv. Atlas 57) plants. Embryogenic callus and plants were produced in three separate experiments; the cultures have retained regenerative capacity for three years after initiation. Our results demonstrate that explants other than immature embryos are embryogenicaUy competent in barley and that regeneration occurs by both somatic embryogenesis and organogenesis.

The concentration of chloride in leaves of ‘Encore’ snap beans (Phaseolus vulgaris var. humilis) and in roots of ‘S‐100’ soybeans (Glycine max (L.) Merr.) varied inversely with nitrate concentration in the nutrient solution. Plants were grown in a greenhouse in perlite cultures automatically irrigated with complete nutrient solution. Although the concentrations of chloride and other anions were varied in some experiments, accumulated chloride was more closely related to nutrient nitrate than to nutrient chloride.

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