Articles
THE EFFECT OF DAY EXTENSIONS WITH DIFFERENT LIGHT QUALITIES ON THE MORPHOGENESIS OF FUCHSIA, PETUNIA AND PELARGONIUM
Daylength was extended to 18 hours with blue fluorescent (B), red fluorescent (R) or incandescent (Inc) light at irradiances of 5.5, 4.2 and 4.9 micromol m-2 s-1 respectively in the 400 to 800 nm wavelength range, given either in the first or the second half of the night.
The rate of elongation growth of Fuchsia was enhanced by the Inc, B and R treatments.
However, in the R treatment the length of the internodes was the same as in the dark controls; internodes in the Inc and B treatments were longer.
In Petunia Inc and B increased elongation growth rate and the final length of the internodes.
In Pelargonium there was a slight increase in plant height (stem plus leaves) with Inc.
In the three species Inc in the first half of the night generally increased elongation more than it did in the second half.
The light treatments had hardly any effect on the number of lateral branches.
The intensity of the anthocyanin ring on the leaves of Pelargonium was decreased by all light treatments in the second half of the night.
Due to a photoperiodic response the time to flowering of Petunia and Fuchsia was shortened in the light treatments.
Less internodes were formed beneath the first node bearing flowers in both species.
In this respect all light treatments were equally effective.
In a similar experiment from April through May there were no effects of the lighting treatments at all.
In this experiment natural daylength was longer, the day extensions were shorter and the mean daily sum of irradiation was twice that of the first experiment.