Plant Micro-Nutrients

Introduction

Nutrition is essential for all living beings. In the absence of proper nutrition, living beings suffer from lack of growth and development. Plants require nutrition too. They require certain elements/minerals in large quantities, while others in relatively lower quantities. Minerals/elements that are required in large quantities by plants are called macronutrients. They are those essential elements, which must generally be present in easily delectable quantity, at least 1 to 10 m per gram of dry matter.Nitrogen (N), Potassium (K), Calcium (Ca), Phosphorus (P), Magnesium (Mg), Sulphur (S), Oxygen (O), Carbon (C) and Hydrogen are called macronutrients, while the ones required in smaller quantities by plants are called plant micronutrients. Both micro and macro nutrients in plants help in their growth and development.

These nutrients play a vital role in several metabolic processes such as photosynthesis, nitrogen reduction and fixation and more, which helps plants to grow. These nutrients are available to plants through soil. If soil is deficient in these nutrients, they are provided externally through manure or fertilizers which contain macro and micronutrients in required quantities. While lack of macro and micronutrients affects growth and development, their excess can also hamper plant metabolism and stagnate development. 

Eight Essential Plant Micronutrients

There are eight micronutrients that are essential for plant metabolism, which includes:

– Boron(B)

– Chlorine(Cl)

– Copper(Cu)

– Iron(Fe)

– Manganese(Mn)

– Molybdenum(Mo)

– Nickel(Ni)

– Zinc(Zn)

These nutrients aid or catalyze various biochemical processes, including nitrogen fixation, production of chlorophyll  resulting in germination, fruiting , overall  growth of crops and more in  plants. The amount of each micronutrient required by plants varies across biochemical processes and across plants. The amount of each micronutrient required by a plant depends a lot on the condition of the soil.

Even though each plant micronutrient is required in a small quantity; they have a significant impact on the growth of plants. The quantity of each micronutrient required for growth varies across plants.

Role of Micronutrients in Plants

Here are some of the major functions performed by the micronutrients in plants.

1. Boron (B)

Boron exists in soil as (Bo3 )3-  anion. It helps in the formation and strengthening of cell walls – which further helps in germination, formation of pollen, flowering, fruiting and other metabolic processes. Plants such as cotton, grapes, cabbage, broccoli, carrot, apple, etc. require boron in large quantities compared to other plants. Deficiency of boron may cause reduced production of seeds and grains.

Boron also regulates supply of sugar and the production of amino acids in plants.

2. Zinc (Zn) 

Zinc exists as Zn2+ cation in soil. It is an essential nutrient for peaches, apples and pecans. Zinc helps in photosynthesis – which helps plants make their food. Deficiency of zinc in plants is generally noticeable by smaller leaves and reduced maturity of plants.

Zinc also helps in balancing plant hormones and regulating activity of auxins.

Zinc is also a vital nutrient for the human body. It is essential for various biochemical processes in the body, including DNA synthesis, protein synthesis, immune function and more.  Our body can’t produce or store, so it has to be supplied through food. Cereals such as quinoa, oats, and legumes such as chickpeas, black grams etc are good sources of zinc and supply zinc to the body.

3. Iron (Fe) 

Iron is one of the most essential micronutrients for plant growth. It works as a catalyst in many biochemical reactions in plants. It is also needed in nitrogen reduction and fixation – an important biochemical process that helps in the growth  of the plants and chlorophyll synthesis.

Nitrogenase – the enzyme that converts atmospheric nitrogen (N2) to usable nitrogen compounds (nitrogen fixation) required in several metabolic processes – needs iron to do so.

Yellowing leaves (also called Chlorosis) generally indicate deficiency of iron in plants. Iron exists as Ferrous (Fe2+) or Ferric (Fe3+) in soil.

4. Manganese (Mn) 

Manganese exists as Mn2+ cation in soil. It helps in the metabolism of nitrogen. Deficiency of manganese is reflected in the slow maturity of the plant and shedding of leaves.

Manganese is also an essential trace mineral for the human body and plants are the major source through which we get it. 

5. Copper (Cu)

Copper exists as Cupric (Cu2+) cation. It strengthens cell walls, catalyzes photosynthesis and helps in the production of seeds and grains. Yellow leaves and slowed growth can be a sign of deficiency of copper.

The human body also needs copper in a small quantity, ranging from 900mcg, depending on the age and gender of the person . It helps in the metabolism of iron, production of neurotransmitters and many other physiological processes.

6. Chlorine (Cl) 

Chlorine exists as Chloride (Cl-) anion in soil. It is found abundantly in nature. Its balanced anion cation concentration. Its deficiency in plants is less common than other micronutrients. In fact, excess of chlorine in plants (chloride – salinity) is reported more, resulting in lower yield and quality of crops/plants.

7. Molybdenum (Mo)

Molybdenum exists as the Molybdate (MnO4 2-) anion in soil. It is involved in the metabolism of nitrogen and building of amino acids in plants. It is part of the nitrate reductase enzyme and the nitrogenase enzyme, required for the reduction of nitrate and for biological nitrogen fixation, respectively. Deficiency of molybdenum is usually associated with the reduced activity of one or more of these enzymes. 

8. Nickel (Ni)

Nickel exists as Ni2+ cation in soil. It activates enzymes in several metabolic processes in plants. It is also essential for activation of Urease – an enzyme required for the metabolism of nitrogen and process urea.

The amount of micronutrients required in a field can be determined by performing a soil test.
A standard soil test helps in determining the quantity of several micronutrients including a few of the above nutrients. Based on the results of the test, appropriate nutrients can be supplied through manures or fertilizers.

Conclusion

Micronutrients in plants are vital for their development, despite being solely required in small quantities.