What nutrients do plants require?

Plants require several nutrients to thrive, categorised into macronutrients and micronutrients. Macronutrients are needed in larger quantities, while micronutrients are required only in trace amounts.

Macronutrients

Carbon

Carbon is a fundamental component of many plant biomolecules, including starches and cellulose. It is fixed through photosynthesis from atmospheric carbon dioxide and is integral to the carbohydrates that store energy in plants.

Hydrogen

Essential for synthesizing sugars and building plant tissues, hydrogen is predominantly derived from water. Hydrogen ions are crucial for creating a proton gradient that drives the electron transport chain in both photosynthesis and respiration.

Oxygen

Vital for cellular respiration, oxygen enables the production of adenosine triphosphate (ATP) from sugars generated during photosynthesis. While plants release oxygen during photosynthesis, they need it for aerobic respiration to break down glucose and produce ATP.

Phosphorus

Key to plant bioenergetics, phosphorus is a component of ATP, necessary for converting light energy into chemical energy during photosynthesis. It also plays a role in enzyme activity, cell signaling, and the formation of DNA, RNA, and phospholipids. Phosphorus is often limited in soils due to its slow release from insoluble phosphates, but plants can enhance uptake through symbiotic relationships with mycorrhizal fungi. Phosphorus deficiency typically manifests as intense green coloration in leaves, with severe cases showing necrosis or a purple hue due to anthocyanin accumulation.

Potassium

Potassium regulates stomatal movement, crucial for water balance and drought resistance. It also activates enzymes involved in photosynthesis and respiration, and aids in building cellulose and forming chlorophyll precursors. Potassium deficiency can lead to necrosis, chlorosis, and increased susceptibility to environmental stresses and pathogens.

Nitrogen

An essential element for protein synthesis, nitrogen deficiency often results in stunted growth and chlorosis. Plants mainly absorb nitrogen in the form of nitrate (NO3–) and convert it to ammonium (NH4+) for amino acid and protein synthesis. Deficient plants may exhibit a purple hue due to anthocyanin accumulation, with older leaves showing symptoms first.

Sulphur

Sulphur is a key component of some amino acids and vitamins and is necessary for chloroplast production. It is also part of the iron-sulphur complexes in the photosynthetic electron transport chain. Sulphur deficiency affects younger tissues first, causing yellowing of leaves and stunted growth.

Calcium

Calcium regulates nutrient transport and activates certain plant enzymes. Deficiency leads to stunted growth and developmental issues.

Magnesium

Magnesium is crucial for chlorophyll production and ATP synthesis. Deficiency can result in interveinal chlorosis, where leaves show discoloration between the veins.

Silicon

Although not essential for all plants, silicon strengthens cell walls, enhancing plant resilience to stress and improving growth, health, and productivity. It helps in drought and frost resistance, reduces lodging, and boosts pest and disease resistance. Silicon is considered beneficial and is under review for official recognition as a plant beneficial substance. It is abundant in the earth’s crust, and plants' ability to take up silicon varies. The element’s distribution within plants is influenced by transpiration rates, and it supports growth by improving leaf erectness and reducing toxicity risks.

Micronutrients

While some elements are directly involved in plant metabolism, there are also beneficial elements that, although not essential, positively impact plant growth. These beneficial elements may stimulate growth or be essential only under specific conditions or for certain plant species.

Iron 

Iron is crucial for photosynthesis as an enzyme co-factor. While not a structural component of chlorophyll, it is vital for its synthesis. Iron deficiency typically leads to interveinal chlorosis and necrosis.

Molybdenum 

Molybdenum serves as a co-factor for enzymes involved in amino acid synthesis and nitrogen metabolism. It is a key component of the nitrate reductase enzyme.

Boron 

Boron plays a significant role in binding pectins within the cell wall, particularly in the rhamnogalacturonan II region. It also contributes to sugar transport, cell division, and enzyme synthesis. Deficiency in boron can cause necrosis in young leaves and stunting.

Copper 

Copper is essential for photosynthesis and is involved in several enzyme processes. Deficiency can result in chlorosis and affects lignin production in cell walls, impacting grain production as well.

Manganese 

Manganese is necessary for chloroplast formation. Deficiency can lead to discolored spots on foliage and other color abnormalities.

Sodium 

Sodium is involved in regenerating phosphoenolpyruvate in CAM and C4 plants and can sometimes substitute for potassium. Its role varies among plant groups:

Group A: High sodium levels can replace potassium and stimulate growth.

Group B: Sodium shows specific but less pronounced growth responses.

Group C: Minimal substitution occurs, with negligible effects from sodium.

Group D: Sodium substitution does not occur.

Sodium can enhance leaf area, improve stomatal function, and support water balance. It impacts various metabolic processes, including C4 metabolism, and can substitute potassium in some functions, such as osmotic regulation and enzyme activation, thus improving crop quality.

Zinc 

Zinc is required for numerous enzymes and is essential for DNA transcription. Zinc deficiency often causes "little leaf" syndrome, where leaves become stunted due to the oxidative degradation of the growth hormone auxin.

Nickel 

Nickel, absorbed as Ni²⁺, is crucial for activating urease, an enzyme involved in nitrogen metabolism. Without nickel, toxic urea levels accumulate, leading to necrotic lesions. In lower plants, nickel activates various enzymes and can substitute for zinc and iron in some enzymatic functions.

Chlorine 

Chlorine is important for osmosis, ionic balance, and also contributes to photosynthesis.

Cobalt 

Cobalt is essential for some plants, such as legumes, where it supports nitrogen fixation in symbiotic relationships with nitrogen-fixing bacteria. Cobalt deficiency can impair protein synthesis in Rhizobium. While cobalt’s direct effects on higher plants are still under investigation, it is clear that it plays a significant role in nitrogen fixation for legumes.