MICRONUTRIIENTS - THEIR FUNCTION IN METABOLISM - GROWTH REGULATION TRANSPORT SYSTEM - THE ROLE OF IRON

 

11

Iron serves a direct role in gathering and moving charged electrons, and is directly responsible for the production of respiration energy.

Cytochromes are a group of iron-keyed enzymes which function as intermediate carriers of electron energy in oxidation processes in the plant. As we have learned, oxidation in a plant is called respiration. We saw how sugar was made from water and carbon dioxide in photosynthesis. Respiration is the oxidation or "burning" of sugars to form carbon dioxide and water. The uptake of oxygen comes from the air. Through respiration, energy is liberated and made available to the energy-using reactions of the plant.

Enzymic cytochromes are similar in structure to leaf chlorophyll or blood hemoglobin. Each cytochrome is moved to action by iron-rich protein bundles. Iron deficiency in some plants is associated with stunting because of the reduced production of respiration energy for growth.

Respiration for the production of growth energy takes place in three steps:

1. The conversion of sucrose sugar to phosphate-enriched fructose sugar.
2. The conversion of fructose-phosphate to pyruvic acid.
3. The burning of pyruvic acid to release carbon dioxide, water and energy.

 

Respiration: Phase 1

Three enzymes and energy-rich phosphate are involved in the first step. Phosphorus is significant here. The plant cannot start to grow until it has started functional photosynthesis, but this must in turn be followed by respiration energy releases for growth. Phosphorus must be readily available, and in large amounts, at the time of plant emergence. This is one reason starter grade fertilizer is high in Phosphorus.

 

Respiration: Phase 2

In the second phase of respiration, the phosphate-enriched fructose is converted to pyruvic acid, and at least six enzymes are known to take part in this portion of respiration. As the plant grows and more energy is needed, adequate phosphorus and iron must be on hand to carry on every transfer cycle in respiration.

 

Respiration: Phase 3

Iron plays an important role in the process of respiration. Energy is developed as cytochrome, the iron-activated enzyme, gathers electrons, mixes them with low-energy phosphate, and discharges them as energy-rich phosphates.

This final phase, the conversion of pyruvic acid to water, carbon dioxide, and energy is one of the most complicated systems in plant metabolism. It is known as the Krebs Cycle – named for the man who first traced its course.

Next Page