MICRONUTRIENTS - THEIR FUNCTION IN METABOLISM - MAKING PHOSPHOLIPIDS - THE ROLE OF MANGANESE
Manganese is thought to activate the enzyme phospholipase, which is active in the synthesis of phospholipids from simpler fat molecules. We should recall that there are three major chemical parts of plants: carbohydrates, proteins and lipids. Lipids are composed of fats, waxes and a third subdivision – the phospholipids. They are fat-like in chemical reaction and are found in all living matter. However, their function is only vaguely understood.
One of the phospholipids is phosphatidic acid. It is formed by the action of manganese-activated phospholipase on phosphoric acid, protein and glycerol. Phosphatidic acid is known to form a part of the membrane of the chloroplast – the band of living matter in leaf cells. The chloroplast itself is known to contain chlorophyll (with magnesium) and layers of other metals and give living plant tissue its green color.
It is obvious that manganese is closely associated with phosphorus fertilization, and this should reflect in your fertilizer program. Solution fertilizer grades give you the best opportunity to incorporate any needed manganese in very close association with every drop of phosphorus.
A deficiency of manganese decreases photosynthesis. The characteristic leaf appearance associated with deficiency is leaf spotting or intervenal yellowing.
Phosphatidic acid is known to form a part of the membrane of the chloroplast. The chloroplast itself is known to contain proteins, protoplasm, and grana. The grana are the disc-shaped platelets that we watched being prepared in the factory reaction where we were studying copper's role in preparing proteins. You will note that the grana are green in color and contain chlorophyl (with magnesium) and layers of other metals.
Each granum is composed of many super-imposed layers.The grana are imbedded in a matrix of protoplasm called stroma. The grana and stroma are surrounded by a limiting membrane at least partially composed of phosphatidic acid.
But now we must prepare ourselves for perhaps the most rewarding experience of our visit to this plant cell factory. Step out here on this balcony and let's watch what happens when sunlight hits these chloroplasts.
Let's examine this complicated process of photostynthesis by seeing what happens when sunlight hits chloroplasts.
The grana which, as we noted, are filled with metals and chlorophyll, have the ability to convert water and carbon dioxide into sugar when energized by light from the sun. The sugars provide energy for plant growth when oxidized during respiration.
Manganese keys the phospholipase enzyme system to provide an envelope for the chloroplasts where photosynthesis takes place. Without photosynthesis there can be no growth. Without an adequate amount of manganese, photosynthesis is greatly limited.
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