| MadSci Network: Botany |
You probably know that plants require carbon dioxide, containing carbon and oxygen, and water, containing oxygen and hydrogen, for photosynthesis. Plants also require at least 14 other mineral nutrients that are mainly absorbed by the roots in the form of ions from the soil solution. Six of the 14 are called macronutrients because they are required in relatively large amounts. They are nitrogen, phosphorus, potassium, calcium, magnesium and sulfur. The micronutrients, required in smaller amounts, are iron, manganese, boron, copper, zinc, chlorine, molybdenum and nickel. Some kinds of plants also require additional mineral nutrients. For example, horsetails require silicon and plants with C-4 photosynthesis require sodium. Most of the 14 mineral nutrients do play a direct role in photosynthesis. For example, nitrogen and magnesium are part of the chlorophyll molecule, nitrogen and sulfur are part of photosynthetic enzymes, and iron is required for chlorophyll synthesis. All have at least an indirect role in photosynthesis because deficiencies of mineral nutrients cause chlorosis (loss of chlorophyll) or stunting of growth. Plants can make all their own vitamins and organic compounds, such as proteins, carbohydrates, DNA, and fats. Several vitamins play a role in photosynthesis. Beta-carotene, the precursor of vitamin A in animals, absorbs light and acts as a supplementary light receptor to chlorophyll. Vitamin C, or ascorbic acid, and vitamin E help protect chloroplasts from oxidation, hence they are called antioxidants. Vitamin K acts as an energy-transfer molecule in the light reactions of photosynthesis. References Micronutrients in a Nutshell Adding vitamin C to a houseplant...
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