| Abstract: | Pith callus tissues were grown under continuous blue (450 mµ),green (545 mµ), red (650 mµ), and ‘white’(full-spectrum) light, and in the dark for 22 days at 27±2°C at energy levels of 15,000 ergs cm–2 sec–1. Mean increases in fresh weight of tissues grown under ‘white’and blue light were significantly greater than those of tissuesgrown in green and red light and in the dark. Tissues grownin the dark yielded mean fresh weight increases significantlylower than tissues grown under blue, red, and ‘white’light. No significant differences were shown between blue and‘white’, red and green, and green and dark treatmentsrespectively. Cell differentiation occurred in all treatmentsonly to the extent of vessel element formation. There were nodifferences in degree of differentiation between treatments. It was proposed that the high-energy reaction of photomorphogenesiswas in operation in the Pelargonium callus tissue. The resultsindicated the presence in the tissue of high-energy photoreceptor(s).The use of high-intensity, incandescent illumination for experimentalprocedures approximating natural conditions of irradiation wasindicated as desirable for pith callus tissues of Pelargoniumzonale var. Enchantress Fiat. |
