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Chemistry of Plant Color
Transcript of Chemistry of Plant Color
Visible light spectrum
Color expression due to pH
Lime is the most widely used method of adjusting pH in soil-domestically (horticulutral lime) and commercially (quicklime and slaked lime) to create stronger bases for construction
Most comes in form of CaCO3 (home use) or CaOH or CaO, CaCO3 (commercial use), which when added water and a pozzolan will create a substance that hardens when exposed to water.
The interaction between the CaOH and silicate materials is called a Pozzalanic reaction
Ca(OH)2 + H4SiO4 → Ca2+ + H2SiO42− + 2 H2O → CaH2SiO4 · 2 H2O
Protecting the Environment
One concern about using lime in mass quantities is the addition of acid in runoff water.
Three precautions to prevent this:
1. Pozzolanic reaction consumes all lime
2. Soil is compacted soon after reaction
3. Calcium Aluminum-Silicate mineral phases formed are insoluble to water
pH and Soil
-Soil pH has a strong effect on plant growth
-Most plants thrive at a pH of 6.0-6.5
Successful growth depends on nutrients needed
-pH too high: Essential nutrients like Iron, Manganese and Aluminum are tied up and unusable
-pH too low: excess [H+] becomes toxic to plants
What effects soil pH?
-Rain leaches ions away
-CO2 can break down into weak acid
-Decaying matter can form strong organic & inorganic acids like Nitric Acid and Sulfuric Acid
Chemistry of Plants
Pigments are molecules with their own absorption spectra.
Chromophore: functional group within the pigment molecule responsible for color. It contains two orbitals where electrons are excited to produce color
Chromophores typically exist in two forms:
1. In conjugated pi systems: electron excitation occurs between pi orbitals spread across alternating single and double bonds. Examples of conjugate pi chromophores are retinenes, azo compounds, lycopene, β-carotene, and anthocyanins.
2. Metal complex chromophores: possess share d-orbitals between transition metals (with incomplete d-shells) and ligands. Examples of such chromophores are the chlorophylls, hemoglobin, and hemocyanin.
Pink: higher pH, less aluminum in soil
Blue: lower pH, affinity for aluminum
The Visible Light Spectrum refers to the colors that the human eyes are capable of seeing/processing.
The typical range of visible wavelengths that the human eye can process is between 400-700 nanometers.
We are able to perceive leafs as green due to the fact that they absorb all colors and reflect green.
Gilbert, T., Kirss, R., & Foster, N. (2013). Chemistry: An atoms-focused approach. W. W. Norton & Company.
Photosynthesis. (2006, October 6). Retrieved April 10, 2015, from http://phototroph.blogspot.com/2006/11/pigments-and-absorption-spectra.html
Reusch, W. (2013, May 5). UV-Visible Spectroscopy. Retrieved April 10, 2015, from http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/UV-Vis/spectrum.htm
Soil pH: What it Means. (2015, January 1). Retrieved April 10, 2015, from http://www.esf.edu/PUBPROG/brochure/soilph/soilph.htm
Technical Papers and Articles. (2015, January 1). Retrieved April 10, 2015, from http://www.griffinsoil.com/ph_of_lime_stabilized_soils
Tucker, R. (2007, July 3). Agronomic Services. Retrieved April 10, 2015, from http://www.ncagr.gov/agronomi/soilph.htm