# Nutrition in Plants The process by which plants obtain and utilize essential substances (nutrients) for growth and metabolic functions. As **autotrophs**, plants synthesize their own organic food from inorganic nutrients like water, carbon dioxide, and minerals absorbed from the environment. ## Nutrient Any substance supplying essential elements for an organism's growth and metabolism. Plant nutrients are primarily inorganic compounds. ## Autotroph An organism that can produce its own food, typically using light (photosynthesis) or chemical energy. Plants are photosynthetic autotrophs. ### Types of Plant Nutrients Plant nutrients are categorized based on the quantity required by the plant. There are 16 essential elements for plant growth. - **Macronutrients:** Required in large quantities (greater than 0.05% of the plant's dry weight). - Carbon (C) - Hydrogen (H) - Oxygen (O) - Nitrogen (N) - Phosphorus (P) - Potassium (K) - Sulphur (S) - Calcium (Ca) - Magnesium (Mg) - **Micronutrients:** Required in very small or trace amounts (less than 0.05% of the plant's dry weight). Also known as trace elements. - Iron (Fe) - Boron (B) - Manganese (Mn) - Copper (Cu) - Molybdenum (Mo) - Chlorine (Cl) - Zinc (Zn) - Nickel (Ni) ### Role of Nutrients and Deficiency Symptoms The absence of any essential nutrient, even a micronutrient, can cause deficiency diseases in plants. | Element (Form Absorbed) | % Mass in Dry Tissue | Major Functions | Early Visual Symptoms of Nutrient Deficiencies | | :--- | :--- | :--- | :--- | | **Macronutrients** | | | | | Carbon ($\mathrm{CO_2}$) | 45% | Major component of plant's organic compounds. | Poor growth. | | Oxygen ($\mathrm{CO_2}$) | 45% | Major component of plant's organic compounds. | Poor growth. | | Hydrogen ($\mathrm{H_2O}$) | 6% | Major component of plant's organic compounds. | Wilting, poor growth. | | Nitrogen ($\mathrm{NO_3^-}$, $\mathrm{NH_4^+}$) | 1.5% | Component of nucleic acids, proteins, and chlorophyll. | Chlorosis at tips of older leaves. | | Potassium ($\mathrm{K^+}$) | 1.0% | Cofactor of many enzymes; water balance; operation of stomata. | Mottling of older leaves, drying of leaf edges; weak stems. | | Calcium ($\mathrm{Ca^{2+}}$) | 0.5% | Component of middle lamella and cell walls; membrane function. | Crinkling of young leaves; death of terminal buds. | | Magnesium ($\mathrm{Mg^{2+}}$) | 0.2% | Component of chlorophyll; cofactor of many enzymes. | Chlorosis between veins in older leaves. | | Phosphorus ($\mathrm{H_2PO_4^-}$, $\mathrm{HPO_4^{2-}}$) | 0.2% | Component of nucleic acids, phospholipids, ATP. | Slow development; thin stems; purpling of veins; poor flowering. | | Sulfur ($\mathrm{SO_4^{2-}}$) | 0.1% | Component of proteins. | General chlorosis in young leaves. | | **Micronutrients** | | | | | Chlorine ($\mathrm{Cl^-}$) | 0.01% | Photosynthesis (water-splitting); water balance. | Wilting; stubby roots; leaf mottling. | | Iron ($\mathrm{Fe^{3+}}$, $\mathrm{Fe^{2+}}$) | 0.01% | Respiration; photosynthesis; chlorophyll synthesis. | Chlorosis between veins in young leaves. | | Manganese ($\mathrm{Mn^{2+}}$) | 0.005% | Formation of amino acids; activates enzymes; water-splitting. | Chlorosis between veins in young leaves. | | Boron ($\mathrm{H_2BO_3^-}$) | 0.002% | Chlorophyll synthesis; cell wall function; pollen tube growth. | Death of meristems; thick, discolored leaves. | | Zinc ($\mathrm{Zn^{2+}}$) | 0.002% | Chlorophyll formation; cofactor of enzymes; DNA transcription. | Reduced internode length; crinkled leaves. | | Copper ($\mathrm{Cu^+}$, $\mathrm{Cu^{2+}}$) | 0.001% | Component of redox and lignin-biosynthetic enzymes. | Light green color in young leaves; stunted roots. | | Nickel ($\mathrm{Ni^{2+}}$) | 0.001% | Nitrogen metabolism. | General chlorosis; death of leaf tips. | | Molybdenum ($\mathrm{MoO_4^{2-}}$) | 0.0001% | Nitrogen metabolism. | Death of root and shoot tips; chlorosis in older leaves. | ### Common Symptoms of Mineral Deficiencies - **Chlorosis:** Yellowing of green plant parts due to a lack of chlorophyll. Caused by deficiency of **nitrogen** and **magnesium**. - **Necrosis:** The localized death of plant tissue. - **Stunted Growth:** Less than normal growth. Caused by deficiency of **phosphorus**, **sulphur**, and **potassium**. ### Managing Soil Nutrients Nutrients can become depleted if the same crop is grown repeatedly. This can be managed by: 1. **Crop Rotation:** Cultivating different crops alternatively in the same soil. 2. **Fertilizers:** Adding natural or synthetic fertilizers to replenish soil nutrients. ### Nutrition of Carnivorous Plants **Carnivorous (or insectivorous) plants** are photosynthetic autotrophs that supplement their nutrition by trapping and digesting insects. - **Adaptation:** This strategy is an adaptation to nitrogen-deficient environments, such as marshy areas. Insects provide a vital source of nitrogen. - **Mechanism:** They have modified leaves that act as traps. Some also have symbiotic bacteria that help break down insect proteins. - **Examples:** *Pitcher plant (Nepenthes pupurea)*, *Venus flytrap (Dionaea muscipula)*, and *Sundew (Drosera intermedia)*. ### Saprophytic Nutrition ### Symbiotic Relationships ### Hydroponics - **Hydroponic culture** is a method of growing plants without soil, using aerated water containing specific, measured nutrients. - It is a useful scientific technique to determine which mineral elements are essential for a plant's growth by selectively removing a nutrient and observing the effects.