| MadSci Network: Botany |
Chlorophyll contains nitrogen as do the dozens of enzymes required for photosynthesis. A major requirement of plants are the approximately 14 mineral nutrients that they absorb mainly as ions from the soil solution. The essential mineral nutrients are nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, iron, manganese, copper, zinc, molybdenum, chlorine, and nickel. Some plants also require sodium or silicon, and plants with biological nitrogen fixation require cobalt for the nitrogen-fixing bacteria. Most of the 14 essential mineral nutrients also play direct or indirect roles in photosynthesis. For example, chlorophyll contains magnesium, ATP contains phosphorus, potassium is involved in stomatal opening and iron is part of several cytochromes in the Z-scheme of the photosynthetic light reactions. Deficiencies of any of the 14 essential mineral nutrients will decrease photosynthesis. Nitrogen deficiency causes chlorosis or yellowing, meaning chlorophyll content drops. For these reasons, the general photosynthesis equation should also include "mineral nutrients" along with light, water, carbon dioxide. Technically, the general equation for photosynthesis should specify "chlorophyll-containing cells" because chlorophyll alone is insufficient for photosynthesis. Chlorophyll extracted from the leaf into a test tube and given light, water, carbon dioxide and mineral nutrients will not support photosynthesis. Reference Iron and Photosynthesis Essential Elements for Plant Growth
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