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  • Author or Editor: Robert N. Stewart x
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Abstract

Coleus cultivars differed in their response to enhanced levels of UV-B. With 80% or greater increase in biologically effective radiation, some distorted leaves developed, anthocyanin pigmentation was decreased, and absorbance at several peaks in the UV region increased. Coleus was less sensitive during seasons of high ambient photosynthetically active radiation (PAR) than during low PAR suggesting photorepair was a factor in the response. None showed a response in height, number of nodes, fresh weight, or dry weight.

Open Access

Abstract

Groups of poinsettia plants (Euphorbia pulcherrima willd. ex Klutzsch) were exposed at different seasons to enhanced levels of ultraviolet (280-320 nm) radiation, 01-13 weighted m W m−2 (UV-B), for 4 weeks in both vegetative and flowering growth stages. None of the cultivars showed any response in height, number of nodes, fresh weight, or dry weight. Some distorted leaves and bracts developed during the seasons of low light intensity but not during seasons of high light intensity, suggesting photorepair during the latter periods. The anthocyanin pigmentation produced in the bracts of flowering plants was partially destryoed by enhanced UV-B, whereas in vegetative plants the pigmentation in petioles was increased. Bracts from many of the treated plants showed increased absorbance in the UV-A and UV-B regions. Cultivars differed widely in their response to enhanced UV-B.

Open Access

Abstract

Eight cultivars of poinsettia, Euphorbia pulcherrima Willd. ex Klotzsch., were exposed to sulfur dioxide under controlled-environment conditions. A new cultivar, ‘Ruff & Reddy’, showed the most overall tolerance while ‘Rudolph’ and ‘Mikkel Blaze’ were least tolerant. The bracts of ‘Annette Hegg’ were injured most by sulfur dioxide, whereas the bracts of ‘Ruff & Reddy’ and ‘Eckespoint C-1’ were not visibly injured at the dosage levels tested. The wide range in tolerance to SO2 among the 8 different genotypes indicates a potential for breeding and selection of tolerant cultivars.

Open Access