Phototropism In Nature
Laboratory studies of phototropism have a bearing upon the life of plants in nature. It is advantageous for a young seedling, such as a coleoptile, to bend toward the light so that its leaves can intercept more sunlight for photosynthesis and grow faster. Phototropism is also related to solar tracking, the orientation of a plant's leaves in response to the Sun. Unlike the response in coleoptiles, which is caused by differential stem growth, solar tracking responses in most species are caused by pressure changes in special cells at the leaf base. Depending on the species and other factors, the blades of a mature leaf may be oriented perpendicular to the Sun's rays to maximize photosynthesis or parallel to the Sun's rays to avoid over-heating and desiccation.
See also Geotropism.
Hart, J.W. Plant Tropisms and Other Growth Movements. London: Routledge, Chapman & Hall, 1990.
Peter A. Ensminger
Science EncyclopediaScience & Philosophy: Philosophy of Mind - Early Ideas to Planck lengthPhototropism - History Of Phototropism Research, Cholodny-went Theory, The Photoreceptor Pigment, Phototropism In Other Organisms