Essential Plant Nutrients and their Functions
The essential elements required for the plants for the continuation of their life cycle are the plant nutrients. The plant nutrients are defined in terms of its involvement in metabolic activities of the plants growth and development whose absence cannot be replenished by the other element. Broadly, 16 different elements play important role in the plants growth. Nitrogen (N), Phosphorous (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Sulfur (S) required in large amount by plants are called macronutrients. The other elements required comparatively in lesser amount are called micronutrients, which include Boron (B), Chlorine (Cl), Copper (Cu), Manganese (Mn), Molybdenum (Mo), and Zinc (Zn). Other elements such as Sodium, Silicon and Selenium are explained as beneficial elements due to their specific functions in the plants.
When the nutrient is deficient, the plant shows the deficient symptoms. The deficient nutrient can be toxic and may show the toxic symptom. Toxic symptoms are generally after luxury consumption in the plants.
Basic Functions of nutrients in plants
Although the functions played by different elements are difficult to generalise, few basic terms in which they play important roles have been mentioned.
N: important component of chlorophyll, vitamins, alkaloids, ATP
P: root growth, photosynthesis and respiration, cell membrane, phospholipids, all nucleic acids, nucleotides
K: maintaining turgidity, opening and stomatal closing,
Ca: For cell wall formation, stem and root apex development, permeability of cell membrane
Mg: important part of chlorophyll, phosphate metabolism, for ribosomal sub units
S: important component of proteins, enzymes, vitamins, amino acids
Fe: chlorophyll production, important in enzyme acids
B: For plant health and growth, uptake and utilization of calcium ions, pollen germination, carbohydrate and sugar translocation
Mn: for photosynthesis, for activation of certain enzymes, Kreb's cycle, IAA
Mo: for nitrogen fixing, nitrogen metabolism
Cl: for photosynthesis, solute concentration, role in photolysis
Cu: for various enzymes, oxidation and reduction in ETS in mitochondria,
Zn: for synthesis of proteins, auxin synthesis, tryptophan
Visual Symptoms of Nutrient Deficiencies and Nutrient Disorders
See : nutrient deficiency in maize leaves
Nutrient Requirements, uptake mechanism
There are three ways of ionic movement from roots to the plants. They include root interception, mass flow and diffusion.
Root interception: when the nutrient comes in direct contact with the root, the root interception can occur. The presence of mycorrhizal fungi, and increase in the root area helps in root interception and factors affecting root growth disrupts the process of root interception. Calcium, magnesium , zinc, manganese are readily up taken through this process.
Mass flow: The movement of water helps in the transportation of nutrients in this process. The more the water flows, the quantifiable amount of nutrients are transported towards the root. Nutrients like Nitrogen, Calcium, Magnesium, Sulfur, Carbon, Boron, Manganese are available through this process to the roots.
Diffusion: The movement of nutrients from higher concentration to lower concentration helps in the transport of nutrient such as phosphorous, potassium, zinc and iron towards the roots. More immobile nutrients such as Phosphorous and Potassium are are transported via diffusion.
Fick's law explains the diffusion rate as dC/dt = diffusion coefficient * cross sectional area of diffusion * concentration gradient
Ionic transport follows symplastic and apoplastic pathway. In symplastic pathway, the nutrients travels through cytoplasm whereas in apoplastic pathway, the nutrients travel inbetween spaces between cell wall.
No comments:
Post a Comment