Nutrients and Nutrient Stress
Author: Parimal Ramesh Udgave

What are Nutrients?
Nutrients are vital for Germination, Growth and Development of plants. It is important to study mechanisms of nutrient or ion uptake process which plays important role for understanding the cellular and molecular flow of the plant system.

Classification of nutrients by chemical groups [Mengel and Kirkby] (1978)

First Group Second Group Third Group Fourth Group
Carbon(C), Hydrogen (H), Oxygen (O), and Nitrogen (N). Phosphorus(P), Boron (B) Potassium (K), Sodium( Na), Calcium (Ca), Magnesium (Mg),Manganese (Mn), Chloride (Cl) Iron (Fe),Zn (Zinc),Copper(Cu) and Molybdenum (Mo)
Organic matter Oxyanions, Phosphate, Borate and Silicate Which control osmotic and ion balance roles Structural Chelates or metalloproteins

What is Nutrient Stress?

Nutrient Stress can be caused by low levels of minerals or excess levels in plant system. Understanding nutrient stress is complex process as we need to consider different aspects which include soil science, ecology, physiology, biochemistry, agronomy and molecular biology. Assessment or chemical analysis of inorganic matter of plant parts doesn’t give clear idea about nutrient required by plants. The plants show diverse requirement of nutrient depending on species, age, soil, ecology and genome of it. Morphological characters are found to be valuable and strong base for conclusion of nutritional status of any plant. For example, yellowing of leaves, darker color of leaves, chlorosis, intervenial chlorosis, and necrosis. Toxicity caused by metals in plant systems normally show characters like stunting of growth and chlorosis. Stunting of growth includes small leaf area or leaf canopy. Modern analytical tools like Inductively Coupled Plasma- Mass Spectrometry (ICP-MS), Inductively Coupled Plasma- Optical emission Spectroscopy (ICP-OES), Laser Ablation- Inductively Coupled Plasma- Mass Spectrometry (LA-ICP-MS), and Atomic Absorption Spectroscopy (AAS) are playing key role in nutrient analysis of soil and plant. They are more precise and accurate. Isotopic profile of a same metal can also be analyzed by these techniques. Comparison or analysis using analytical techniques of both soil and plant can give us accurate requirements of nutrients for a particular plant.

Consequences of different nutrient stress condition in plant is enlisted below

Nutrient or Mineral Nature and Availability Deficiency symptoms Excess symptoms
Nitrogen (N) Important growth limiting factor and component of amino acids, proteins, nucleic acids, chlorophyll in plants.
Availability- N2, NO3-, NO-2, and NH4 +.
Disturbed Root: Shoot Ratio, Short lateral branches, Stunted growth, small leaves, and Old leaves show chlorosis, Chloroplast disintegration, Necrosis at later stages, death at last. Succulent growth, dark green leaves, thick and brittle nature of leaves
Phosphorus (P) Component of nucleic acids, phosphorylated sugars, Lipids, and proteins. Aid in biological reactions by carrying energy.
Availability- H2PO4- (Need low pH) and HPO42- (Need High pH) (Inorganic nature and availability depends on soil pH. Inaccessible and unavailable form of Phosphorus leads to phosphorus deficiency
Shoot and Root growth (Observed more in Shoots as compared to roots but it does, Affects formation of reproductive organs ,Stunted growth, dark blue green and purple colored leaves, abnormal leaf shape, lower number of leaves, decreased primary root development and increase in development of lateral root formation, Induces Iron and zinc deficiency Leads to toxicity if present more than 1%. Higher levels lead to decrease in yield
Potassium (K) Monovalent cation (K+) and essential for Membrane K+ Channels/ Transport of K +. Promotes cell elongation, control osmoregulation, promote photosynthetic rate, control photosynthates transport, protein synthesis and enzyme activator for 45 enzymes in metabolic process. Reduced growth, underdevelopment of nodes, chlorosis and necrosis of older leaves and then younger leaves, plants become susceptible to lodging and drought. Leads to nitrogen deficiency and interferes with uptake of Ca2+ and Mg2+.
Sulfur (S) Sulfur is constituent of cysteine and methionine that’s why it is important part of proteins, Sulphur containing amino acids acts as precursors for co-enzymes, intermediatery metabolites and redoz controllers, acts as prosthetic group of ferredoxin, biotin and thiamine pyrophosphates. Availability- In the form of SO4 2- Decreases hydraulic conductivity of roots and photosynthesis , Decrease in chlorophyll and protein content, hampered shoot growth as compared to roots, Induces accumulation of starch. Reduces plant growth which results in thin dixe of stems and plants become rigid and brittle, Reduced growth rate and dark green colour of leaves.
Calcium (Ca2+) Calcium is important in binding of different organelles of plant cell. Calcium is present in cell wall, cytosol, plasma membrane, Endoplasmic reticulum and vacuoles. It is required for root elongation, bridges phosphate, phospholipids and proteins. Calcium controls and stimulate alpha –amylase activity in germinating seeds, acts as enzyme activator for NAD Kinase, adenylate cyclase and membrane bound ATPase. Availability- CaCO3, CaO, and Ca(OH) 2 Initial symptoms can be seen on growing tips and young leaves. Tips and young leaves become chlorotic followed by necrosis of leaf, Shedding of fruits and buds. Interferes with Mg2+ absorption, it makes other nutrients unavailable by precipitating them.
Magnesium (Mg2+) Magnesium interact with nucleophillic ligands through ionic bonds, Regulation of cellular pH, Cation-anion balance, clustering of ribosome units, RNA polymerase, PEP carboxylase and gluthione synthetase require magnesium need magnesium for working, Availabilty- water soluble and exchangebale Mg 2+ Reduced chlorophyll pigments. Accumulates starch, chlorosis in older leaf intervenes, colour of old leaves changes to reddish-purple and tips and margins become necrotic. Drought condition raise high magnesium concentrations, small necrotic spots on older leaves, young leaves may show spotted appearance,
Iron (Fe) Component of heme proteins, cytochromes, cytochrome oxidase, catalase, peroxidase, leghaemoglobin and nonheme proteins, necessary for biosynthesis of chlorophyll, acts as enzyme activator, important in biological redox systems, Significant effects on chloroplasts and protein content, ribose number lowers, starch and sugar contents also falls which results in low chlorophyll content, reduced regeneration of RUBP, young leaves become white because of low chlorophyll amount, Bronzing, stunted aerial and stunted top and root growth.
Manganese (Mn2+) Manganese is important for phosyntheis, redox processes, and hydrolytic reactions, it forms complexes with different biological molecules and participates in metabolic processes, manganese can also substitute Mg2+ specially in phosphorylating and group transfer reactions, manganese activates different enzymes which are related to secondary metabolites production and aromatic amino acids. Availability- Ferric (Fe3+) and Ferrous (Fe 2+) Results in lowering in amount of soluble carbohydrates, reduced growth of roots, induces accumulation of soluble nitrogen wastes, initial symptoms appears on younger leaves, monocot leaves shows greenish grey spots, Dicots shows yellow spots on leaves, Chlorosis in young leaves, Mn2+ induces Fe 2+ deficiency, Interveinal chlorosis, and necrosis and necrosis, crinckle leaf symptoms,
Zinc (Zn) activator of several enzymes, DNA and RNA metabolism, protein synthesis, auxin metabolism and membrane integrity, important role in DNA replication,transcription and regulation of gene expression
Availability- Zn2+
decreases protein synthesis and results in the accumulation of amino acids and amides Stunted growth, interveinal chlorosis in young leaves, brownish and necrotic roots