Mineral Requirements of Plants

Mineral requirements of plants vary from one plant to another. The area, climate, and nutrients present in the soil also play a key role in the mineral salts needed by plants. Plants soak in minerals via roots that transport them to leaves via stems and branches. The modern techniques used to detect minerals and their content in different plans suggest that some plants even store gold, selenium, and radioactive minerals like strontium. 

However, the question is whether all the minerals that plant stores are required for its survival or functions. Only a few elements or minerals are absolutely essential for growth, reproduction, and metabolic activities. We can divide these essential elements into two main categories viz. micronutrients and macronutrients. 

Micronutrients: When a plant requires elements in trace or minute quantities, they are referred to as micronutrients. The minerals like Zinc, Manganese, Boron, Copper, Nickel, Chlorine, Iron, etc. are some of the micronutrients found in plants.

Macronutrients: The elements found in relatively higher quantities in plants are referred to as macronutrients. Oxygen, Nitrogen, Hydrogen, Sulphur, Calcium, Magnesium, Phosphorus are some of the macronutrients found in plants. 

Minerals needed for photosynthesis 

Mineral elements necessary for the synthesis of chlorophyll i.e. for photosynthesis can also be identified easily these days. Some of these minerals are highlighted below:

Calcium: Calcium is a macronutrient that is among the few minerals needed for photosynthesis. It also plays a vital role in cell wall synthesis that happens during the division of plant cells. Found more in the older leaves, it ensures that the cell membranes function properly. By controlling some enzymes it helps in regulating some of the metabolic activities as well. 

Magnesium: Magnesium is one of the mineral elements necessary for the synthesis of chlorophyll. It stimulates the enzymes responsible for photosynthesis. Also, the RNA and DNA synthesis also need magnesium. It is one of the components of chlorophyll’s ring structure and also controls the structure of the ribosome. 

Manganese: Manganese stimulates enzymes responsible for the metabolism of nitrogen. It also activates the enzymes required for respiration and photosynthesis. During photosynthesis, it splits water to release oxygen which is considered as its most important in plants. 

Chlorine: Chlorine also plays a role in the division of water to release oxygen that is essential for photosynthesis. 

How important are minerals for plants?

Hydroponics is the study that demonstrates that plants can grow in a soilless medium if we supply the essential minerals and nutrients through water. This study was carried out way back in 1860 by a German botanist named Julius von Sachs. The mineral salts needed by plants can be supplied through pipes and a pump. This research is important in today’s context when there is limited soil, area, and resources available for cultivating crops.

Through hydroponics, modern infrastructure, and technology, crops can be grown in vertical columns to reduce space. Also, the nutrients can be supplied through a soilless medium or solution that is infused with the minerals required by plants. Some agro tech firms have been conducting extensive research to develop newer methods and techniques through hydroponics. This phenomenon explains that plants can survive without soil but not without the minerals present in it. 

Influx & Efflux

The absorption of mineral salts needed by plants takes place via two methods viz. active and passive. During the passive intake, the outer cells of the plants take up ions quickly. These outer cells are known as apoplasts. On the other hand, the active intake happens through the inner cells known as symplasts. This process happens at a slower pace. 

When the ions enter or get released through symplasts, it results in energy expenditure due to which is known as the active intake. The movement of ions in the apoplasts happens via ion channels. When the ions move inward o.r. inside plant cells, the process is known as influx.  When the ions move outward through the plant cells, the process is known as efflux. The general term used to refer to the movement of ions is called flux. 

Biological Nitrogen Fixation 

Nitrogen is present sufficiently as N2 in the air. However, only a handful of living organisms can use it in this form. When nitrogen gets reduced to ammonia through living organisms, the process is known as biological nitrogen fixation. Some species of prokaryotic contain nitrogenase that reduces nitrogen. Therefore, these microbes are referred to as nitrogen fixers. 

These microbes are either symbiotic or free-living. Azotobacter, Rhodospirillum, Nostoc, Anabaena, etc. are examples of free-living N2 fixers. 

Symbiotic Nitrogen Fixation 

The biological association that fixes nitrogen through a symbiotic process is known as Symbiotic Nitrogen Fixation. For example, the legumes of sweet peas, lentils, alfalfa, etc. form an association with the bacteria like Rhizobium species (rod-shaped) on the roots in the form of nodules. 

The outgrowths located on the roots are known as nodules. The central part of these nodules is found to be red if you happen to cut them. Sometimes, they are pink. The central part becomes red or pink due to leg-hemoglobin or leguminous hemoglobin.