Chloroplast movement in Alocasia macrorrhiza

Chloroplast movements in a rainforest understory plant Alocasia macrorrhiza (L.) G. Don are striking, creating changes in leaf transmittance that are visible to the naked eye. We have characterized the light requirements for these changes and the resulting changes in light penetration to different cell layers within the leaf and through the entire thickness of the leaf. Plants were grown either in a relatively constant, growth-chamber environment or in a variable, greenhouse environment. Irradiance-response curves for chloroplast movement were the same for both groups of plants, saturating at about 1000 μmol m -2 s -1 , though only the greenhouse-grown plants normally encountered light sufficient to drive the movement. Chloroplast movement caused changes in whole-leaf transmittance on the order of a few percent across the entire visible spectrum. Transmittance changes were larger within the leaf, especially directly under the palisade layer. Chloroplast movement could be manipulated experimentally by removing blue wavelengths from the spectrum of incident light or by treating with cytochalasin D.