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The response of `Bright Golden Anne' chrysanthemum plants grown under CuSO4 spectral filters to exogenous GA3 application was evaluated to determine the relationship between gibberellins (GAs) and carbohydrate levels. The CuSO4 filters removed far red (FR) wavelengths of light and increased red: far red (R:FR), blue: far red (B:FR), blue: red (B:R) ratios, and phytochrome photoequilibrium (Ø) values of transmitted light compared to water (control) filter. Plant height, internode length, and leaf and stem dry weights were significantly reduced by light passing through CuSO4 filters in spring and summer seasons. Weekly applications of exogenous GA3 reversed the reduction in height and internode length induced by CuSO4 filters. Plants grown under CuSO4 filters responded more to exogenous GA3 application with respect to height and internode length, suggesting that the sensitivity to GA was not lowered. Light passing through CuSO4 filters reduced the carbohydrate levels, but the response varied with the season. Weekly GA3 application increased the carbohydrate levels, but did not totally reverse the reduction in carbohydrate levels under the CuSO4 filters. Although GA3 application increased the carbohydrate levels partially in CuSO4 filter-grown plants, the inhibition of GAs may not be solely responsible for reduction of carbohydrate levels under CuSO4 filters, showing that exogenous GAs and carbohydrate levels are not well correlated under CuSO4 spectral filters.
The influence of removal of specific wavelengths [red (R), blue (B), and farred (FR)] from sunlight on the height of chrysanthemum plants was investigated by overlaying Roscolux™ colored acetate films on 4% CuSO4 or water (control) spectral filters. CuSO4 filters removed FR wavelengths and significantly reduced plant height and internode length compared to control plants that received B, R, and FR wavelengths of light. Plants grown under Roscolux blue filters did not receive R light and were significantly taller compared to plants from any other treatments. Plants grown under Roscolux red filters did not receive B light and were significantly shorter compared to plants from other treatments. Leaf area, leaf dry weight, and stem dry weight were highest in plants grown under Roscolux red and control filter combination. The amount of leaf chlorophyll and the ratio of Chl A: Chl B was highest in plants grown under Roscolux blue filters. In general, plants that received FR light (control + film) were taller than the plants that did not receive FR light in the corresponding (CuSO4 + film) filter combination. The influence of removal of specific wavelengths on plant height control and developmental physiology will be discussed.