Functions of the plant
Copper is absorbed by the plants mainly as active form such a Cu2+ and some cases in complex form. It presents an antagonism with Zn2+ at the absorption level.
Copper is associated with several enzymes, as activator or being part of them.
This element participates in a great number of processes (oxidation/reduction). As example, it acts in the ascorbic oxide enzymatic systems, being responsible for the oxidation of the ascorbic acid (Vitamin C) to dehydroascorbic. Then, since this vitamin exerts its protector effect over the oxidation.
Copper intervene in the nitrogen and glucids (carbohydrates) metabolism.
This nutrient favorably influences the atmospheric nitrogen fixation of legumes.
Copper is an essential nutrient in the bio-element balance which in the plant regulates transpiration.
Cu deficiencies are shown as:
Wilting of the young leaves, curling of the leaves and petioles and stems inclination. Leaves are twisted, become brittle and fall down.
Chlorosis and other secondary symptoms (chlorosis not always appears).
Reduction of lignification. The non lignified xylem vessels are compressed by the neighboring tissues, then the water and solutes transport cannot be utilized.
From all microelements, Cu is the most difficult to diagnose due to the interference with other elements (P, Fe, Mo, Zn, S, etc).
Citrus and fruit trees plantations, with an excess of phosphorus fertilizer, can present shortage of Cu.
Cu is utilized as fungicide and algaecide in tanks (ponds) and channels. Even though superior plants are less sensible, these products can produce phytoxicity at slightly higher levels than of the needed in plant nutrition.
In cases of toxicity (superior values in the soil to 300 mg/kg) alterations are shown in the roots, which tend to loose vigor, acquire a dark color, swollen and cease their development.
Also the excess of copper can originate iron deficiency. This is believed that Cu in excess participates in reactions that affect the stage of Fe oxidation, limiting its absorption and translocation within the plant. Another effect of excess of Cu is the reduction of the P absorption.