Plant growth with new fluorescent lamps

Summary Bean and marigold plants were grown to maturity under several kinds of fluorescent lamps to evaluate the effects of spectral differences on development and reproduction. Six kinds of lamps were tested including five lamps that were used in closely related experiments on tomato seedling growth (Thomas and Dunn, 1967). Evaluation was by fresh- and dry-weight yields of immature and mature pods, and of vegetative tops of plants for bean; and by flowering and fresh-and dry-weight yields for marigold.Bean plants grown under two experimental lamps, Com I and IR III produced significantly higher fresh- and dry-weight yields of both mature and total pods than under Warm-white lamps. This effect could be attributed largely to the considerable energy emitted by the experimental lamps in the red and far-red, as compared to a larger emission in the green and blue for the Warm-white lamps. The differences in the yields for immature pods and vegetative portions of the mature tops were not significant.In a comparison of the effects of three experimental lamps with those of three commercial lamps on growth response of bean plants, the yields were in general higher for the experimental lamps, except for immature pods. The yields of vegetative tops were significantly greater for the 78/22 lamp over the yields for all other lamps. The larger proportion of red and far-red light emitted by the experimental lamps is again the probable cause of the higher yields with these lamps.Two sets of experiments on growth and flowering of marigold under various experimental and commercial lamps were largely inconclusive although there was some indication of beneficial effects by the experimental lamps.In general, the results with bean agree with those for tomato (Thomas and Dunn, 1967), in that best growth was obtained with a lamp high in red light emission, a moderate amount in the far-red, and very little in the blue part of the spectrum.This research was submitted by the senior author in partial fulfillment of the requirements for the M.S. degree in Botany at the University of New Hampshire.Published with the approval of the director of the New Hampshire Agricultural Experiment Station as Scientific Contribution No. 398. This study was part of the Northeast Regional Project, NE-35, Analysis of Northeastern Climatic Variables and Their Relationships to Plant Response.