End of day far-red light reverses height reduction of chrysanthemum induced by CuSO 4 spectral filters

Abstract

The response of cultivars ‘Bright Golden Anne’ (‘BGA’) and ‘Spears’ chrysanthemum plants to end of day-red (EOD-R) and end of day-far-red (EOD-FR) light was evaluated to determine the involvement of phytochrome in the regulation of plant morphology under CuSO 4 filters. The CuSO 4 spectral filters removed FR wavelengths and hence, increased the red:far-red (R:FR), blue:far-red (B:FR) and blue:red (B:R) ratios (R = 600–700 nm ; FR = 700–800 nm ; B = 400–500 nm) and ф of transmitted light compared with water (control) filter. Control plants were shaded with cheese cloth so as to attain the same photosynthetic photon flux (PPF) as in the CuSO 4 chamber. Light transmitted through the CuSO 4 filter significantly reduced height, internode length and stem dry weight of cvs. ‘BGA’ and ‘Spears’ chrysanthemum plants. However, the degree of response varied with the cultivar. Exposure to EOD-FR reversed the reduction of plant height, internode length and the stem dry weight caused by the light transmitted through CuSO 4 filters to a level comparable with plants that received no EOD treatment under control. Exposure to EOD-R light reduced the height and stem dry weight of ‘BGA’ plants grown under the control filter, but had no effect under the CuSO4 filter. Exposure to EOD-FR did not significantly alter height and stem dry weight under control filters. In ‘Spears’ plants, EOD-R caused stem dry weight reduction under control filters, but did not reduce stem or internode elongation. The results suggest that phytochrome may be involved in controlling plant response under CuSO 4 filters. However, there is evidence to indicate that an additional mechanism may be acting on stem/internode elongation.