Fiber‐optic Plant Tissues: Spectral Dependence in Dark‐grown and Green Tissues*

The fiber‐optic properties of etiolated plant tissues can be used to detect and characterize pigment absorption in vivo . Transmission spectra of light guided through several monocot and dicot etiolated tissues show a decreasing red/far red ratio with increasing tissue length. Absorption bands attributable both to vacuolar pigments such as anthocyanins and to chloroplast pigments lead to the conclusion that the guided light passes through both vacuole and cytoplasm. As etiolated tissue becomes green under white light treatment, the red/far red ratio also changes, the nature of the change depending upon the tissue involved. The blue/red ratio also changes both with increasing length of etiolated tissue and during the greening process, with the changes again dependent on the tissue involved. The spectral dependence of the light‐guiding phenomenon in dark grown and green plants may have implications for physiological responses mediated by phytochrome.