Effects of light quality and temperature on the growth and development of geraniums

摘要

The effect of light quality on the growth and development of geranium (cv. Century Rose) was examined in three different glasshouse temperatures i.e., 16oC, 21oC or 24oC under natural light conditions. To alter light quality, five different colour filters i.e. blue and red absorbing (088), blue absorbing (101), two partially blue absorbing (109 and 110) and red absorbing (117) were used, with clear polythene as a control. Spectral filters as well as temperature considerably affected different growth parameters. Plant height, internode length, leaf area and flowering were significantly affected by the spectral filters as well as the temperature. In terms of the effects of the presumed photoreceptors, the data analysis indicated that plant height and internode length in geranium was regulated by the action of cryptochrome (blue acting photoreceptor) and not the phytochrome. However, time to flowering was affected by a combined action of phytochrome and cryptochrome, since the filters with high blue transmission and high phytochrome photoequilibrium resulted in early flowering. Simple models were created, through applying multiple regression technique, to predict the influence of spectral quality and temperature on plant height, internode length and time to flowering in geranium. The models could be applied to simulate the potential benefits of spectral quality and temperature in manipulation of growth and flowering in geranium. These will help in designing greenhouse cladding materials for regulation of plant growth in an environment friendly manner.