The Development of Solid Spectral Filters for the Regulation of Plant Growth

Abstract

Phthalocyanine derivatives have been prepared and incorporated into polymer films for use as spectral filters for the modification of plant growth. The unusual absorption characteristics of phthalocyanines, notably the narrow absorption band in the visible region of the electromagnetic spectrum, allows the selective filtering of wavelengths necessary for excitation of either of the two isomeric phytochrome species. The resulting change in the photostationary state for the phytochrome is shown to have a marked effect on the growth characteristics of both chrysanthemums and antirrhinums. Chrysanthemums (short-day plants) grown under a far-red-absorbing film showed a reduction in height (≈14%) and internodal length compared to those grown under a red-absorbing film or a control with no absorption in the visible part of the spectrum; both leaf number and time to flowering were not affected by the presence of the spectral filter. For antirrhinums (long-day plants) both a reduction in height and a substantial increase in leaf area (70%) of the plants grown under the far-red-absorbing film were observed, although flowering was delayed. The potential of these filters as replacements for chemical plant growth regulators is discussed. Show more