Using Magnesium to Boost Photosynthesis
Everyone knows that light is the limiting factor for plant growth. But did you know that magnesium plays a key role in photosynthesis and the efficient use of light? Magnesium is the central element in chlorophyll, the green pigment in plants. When the plant is given full-spectrum light, the chlorophyll molecules absorb the red and blue portions of the light spectrum, and the green light is reflected from the leaves. That’s why plants appear green to the human eye. Horticultural grow lights must include both the blue and red ends of the spectrum for the plants to grow normally, and they must have enough intensity to provide the energy that plants need for photosynthesis. Chlorophyll in the leaves transfers the light energy into the chemical energy necessary for life.
Magnesium is the Key Ion in Chlorophyll
The chlorophyll molecule includes a heme group in its central structure, with a magnesium ion electrically bound in its center. Ironically, red blood cells also contain a heme group (hemoglobin), but the central element is iron instead of magnesium. It’s actually the iron in hemoglobin that makes blood red, while magnesium makes chlorophyll green! Magnesium is so important to photosynthesis that if there is a magnesium deficiency, plants will remove magnesium ions from the chlorophyll in the lower leaves, and translocate it to the upper leaves where the plant needs it the most. That’s why magnesium deficiency shows up as interveinal chlorosis in the lower leaves first. The veins stay green, but the leaf tissues turn yellow from the lack of magnesium.
Magnesium is Critical for Plant to Use CO2
Magnesium is required to activate two key enzymes for the efficient functioning of chlorophyll. The first enzyme is called RuBP carboxlyase. During photosynthesis, the plant takes in carbon dioxide through the leaves and combines it with water from the roots to make simple sugars, with oxygen and water vapour as byproducts. RuBP carboxylase is the enzyme that assimilates the carbon, so adequate magnesium is critical for a plant to use the carbon dioxide in the air.
Magnesium is Responsible for the Transport of Sugars
Magnesium also activates the enzyme that loads sugars into the “phloem” vessels. Phloem transports sugars from the leaves downward throughout the plant. The transported sugars are then stored in the roots and fruits, or they are used for the immediate energy requirements of the plant. Without phloem loading, the sugars would stay in the leaves, locked up as starches in the chloroplasts. So magnesium is not only responsible for the production of sugars, it’s also responsible for the transport of sugars for use by the plant.
Use RAW Cal/Mag to Correct Magnesium Deficiency
Magnesium is very mobile in the plant. It can be taken upward from the roots in the xylem vessels, and it can be transported downward from the leaves in the phloem vessels. (By the way, to remember the difference between xylem and phloem, remember that “xy” rhymes with “high”, and “phlo” rhymes with “low”.) So magnesium deficiency can be corrected with either a root drench or a foliar feed. During times of high-energy demands by the plant, such as during the accumulation of sugars during fruiting and flowering, using RAW Cal/Mag can be very beneficial to your plants!
Harley N. Smith
Further Boosting your Plants Photosynthesis
There a number of things you can do to significantly boost your plants photosynthetic functions. To learn more read our article on boosting your plants photosynthesis.