Plant Science and Agriculture
Overview
Plant Science and Agriculture is a high-scoring topic in SSC CGL/CHSL General Science. It covers plant anatomy, photosynthesis, plant hormones, nutrition, crop types, and agricultural practices. Questions frequently test knowledge of scientific names, plant processes, soil types, fertilizers, and important crops of India. A solid grasp of these concepts helps candidates score quickly in the General Awareness and Science sections.
Typed Notes
Photosynthesis and Plant Nutrition
Photosynthesis occurs in two stages: Light Reactions (in thylakoid membranes) producing ATP and NADPH, and Dark Reactions/Calvin Cycle (in stroma) producing glucose. Chlorophyll absorbs red and blue light, reflecting green. Plants also perform respiration, releasing CO₂. Transpiration is water loss through stomata, regulated by guard cells. Insectivorous plants like Pitcher Plant (Nepenthes) and Venus Flytrap obtain nitrogen from insects due to nitrogen-poor soil. Parasitic plants like Cuscuta (Amarbel) lack chlorophyll and depend on host plants for nutrition.
Plant Hormones and Their Functions
Auxin (IAA) is produced at shoot tips and promotes cell elongation; it causes phototropism and geotropism. Gibberellins promote stem elongation, seed germination, and break dormancy — used commercially in sugarcane to increase yield. Cytokinins promote cell division and delay leaf senescence (ageing). Abscisic Acid (ABA) is called the 'stress hormone' — it closes stomata during drought and promotes seed dormancy. Ethylene is the only gaseous hormone; it promotes fruit ripening and is used to ripen bananas commercially. Exam tip: Remember ABA = Abscission/dormancy.
Crops, Soil and Agricultural Practices
India's major soil types: Alluvial soil (most fertile, found in Indo-Gangetic plains, ideal for wheat and rice), Black/Regur soil (Maharashtra/MP, ideal for cotton, retains moisture), Red soil (iron-rich, Deccan plateau), Laterite soil (leached, found in Kerala/Karnataka). Green Revolution (1960s) introduced High-Yielding Variety (HYV) seeds; Norman Borlaug developed HYV wheat; M.S. Swaminathan is called the Father of Green Revolution in India. NPK fertilizers provide Nitrogen (leaf growth), Phosphorus (root/flower), Potassium (overall health). Urea contains 46% nitrogen — highest among common fertilizers.
Important Plant Facts for SSC Exams
Xylem transports water and minerals upward (unidirectional); Phloem transports food/sugars in both directions. The process of water movement up the stem against gravity is explained by Cohesion-Tension theory. Osmosis is movement of water from lower to higher solute concentration across a semi-permeable membrane. Tallest tree: Sequoia (Redwood); Largest seed: Coco-de-mer; Smallest flowering plant: Wolffia. Scientific name of Rice: Oryza sativa; Wheat: Triticum aestivum; Maize: Zea mays; Potato: Solanum tuberosum. Botany father: Theophrastus. Study of fruits is Pomology; study of flowers is Floriculture.
Key Concepts
Revision ke liye ek nazar — exam se pehle yahi padhna hai.
- 01Photosynthesis equation: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂; chlorophyll (in chloroplasts) is the pigment responsible.
- 02Plant hormones: Auxin (cell elongation), Gibberellin (stem growth/seed germination), Cytokinin (cell division), Abscisic Acid (dormancy/stress), Ethylene (fruit ripening).
- 03Nitrogen fixation: Rhizobium bacteria in root nodules of legumes fix atmospheric N₂; Blue-Green Algae (Cyanobacteria) also fix nitrogen in paddy fields.
- 04Kharif crops (sown June–July, harvested Oct): Rice, Maize, Cotton, Jowar; Rabi crops (sown Oct–Nov, harvested March–April): Wheat, Barley, Mustard, Gram.
- 05Vitamins from plants: Vitamin C (Amla/Citrus), Vitamin A precursor Beta-carotene (Carrot), Vitamin K (Green leafy vegetables); deficiency of Vitamin C causes Scurvy.
Questions & Solutions
Pehle khud try karo — phir solution kholo. Yahi tariqa topper banata hai.
Which plant hormone is responsible for fruit ripening and is used commercially to ripen bananas?
What is the nitrogen content percentage in Urea fertilizer, and why is it significant?
Name the scientist called the 'Father of Green Revolution in India' and mention one key contribution.
Differentiate between Kharif and Rabi crops with two examples each.
What is the role of Rhizobium bacteria in agriculture, and in which crops is it found?
Plant Science for SSC covers photosynthesis (chlorophyll, Calvin cycle), five plant hormones (Auxin, Gibberellin, Cytokinin, ABA, Ethylene), Kharif vs Rabi crops, soil types (Alluvial, Black, Red, Laterite), nitrogen fixation by Rhizobium, Green Revolution led by Swaminathan in India, and key scientific names of crops. Xylem carries water; Phloem carries food. Urea has the highest nitrogen content (46%) among fertilizers.
Chapter-end quiz
4 MCQsOption tap karo — turant pata chalega sahi ya galat, explanation ke saath.
Q1.Which of the following is the scientific name of Wheat?
Q2.Which soil type is best suited for cotton cultivation in India?
Q3.The process of photosynthesis takes place in which part of the plant cell?
Q4.Which plant hormone is known as the 'stress hormone' that promotes seed dormancy and closes stomata during drought?
Mark karo — dashboard par progress dikhega.