☀️ Photosynthesis in Higher Plants
| Category | NCERT Examples | Key Feature / Pathway |
|---|---|---|
| \(C_{3}\) Plants | Wheat, Rice, Barley, Oats, Soya bean, Tomato, Bell pepper | First stable product is a 3-carbon compound (3-PGA). |
| \(C_{4}\) Plants | Maize, Sorghum, Sugarcane, Millet | Possess Kranz anatomy; no photorespiration. |
| CAM Plants | Pineapple, Cactus, Sedum, Opuntia, Sisal | Scotoactive stomata (open at night to save water). |
| Primary \(CO_{2}\) Acceptor | RuBP (\(C_{3}\) pathway), PEP (\(C_{4}\) pathway) | RuBP is 5-carbon; PEP is 3-carbon. |
| First Stable Product | 3-PGA (\(C_{3}\) pathway), OAA (\(C_{4}\) pathway) | 3-Phosphoglyceric acid vs. Oxaloacetic acid. |
| High \(CO_{2}\) Responders | Tomato, Bell pepper | Greenhouse crops grown in \(CO_{2}\)-enriched air for higher yield. |
| Photosynthetic Pigments | Chlorophyll a, Chlorophyll b, Xanthophylls, Carotenoids | Chlorophyll a is the chief reaction centre pigment. |
🌱 Respiration in Plants
| Category | NCERT Examples / Intermediates | Key Significance / RQ Value |
|---|---|---|
| Anaerobic Organisms | Saccharomyces cerevisiae (Yeast), Lacto_bacillus | Undergo fermentation (alcoholic or lactic acid). |
| Respiratory Substrates | Carbohydrates, Proteins, Fats, Organic acids | Carbohydrates are the most preferred substrate. |
| RQ = 1.0 | Carbohydrates (Glucose) | Equal volume of \(CO_{2}\) evolved and \(O_{2}\) consumed. |
| RQ < 1.0 (0.7) | Fats (e.g., Tripalmitin) | Oxygen consumption is higher than carbon dioxide release. |
| RQ = 0.9 | Proteins | Broken down into amino acids before entering respiration. |
| RQ > 1.0 (1.33) | Organic Acids (e.g., Malic acid, Oxalic acid) | Contain more oxygen in their molecular structure. |
| Amphibolic Pathway Linkers | Acetyl CoA (Fats/Proteins), \(\alpha \)-ketoglutaric acid | Acetyl CoA links fat breakdown to the TCA cycle. |
🌱 Plant Growth and Development (PGRs & Responses)
| Plant Hormone (PGR) | NCERT Source / Discovery | High-Yield NCERT Examples & Applications |
|---|---|---|
| Auxins | Human urine, Oats (Avena curvature test) | • Natural: IAA, IBA • Synthetic: NAA, 2,4-D (Weedicide for dicot weeds) • Rooting in stem cuttings, apical dominance, xylem differentiation. |
| Gibberellins (\(GA\)) | Gibberella fujikuroi (Bakanae/foolish seedling disease) | • \(GA_{3}\): Increases stalk length of grapes, elongates sugarcane stems. • Delays senescence (extends shelf life), speeds up malting process. |
| Cytokinins | Herring sperm DNA (Kinetin), Corn kernels (Zeatin) | • Promotes nutrient mobilization, delays leaf senescence. • Overcomes apical dominance, induces lateral shoot growth. |
| Ethylene | Ripening oranges (volatile substance) | • Ethephon (Liquid source): Hastens fruit ripening in tomato/apple. • Thinning of cotton/walnut, promotes female flowers in cucumbers. |
| Abscisic Acid (ABA) | Inhibitor-B, Abscisin II, Dormin | • Stress Hormone: Closes stomata during water stress. • Induces seed dormancy, acts as a general plant growth inhibitor. |
⏱️ Photoperiodism & Seed Germination
| Category | NCERT Examples | Key Feature |
|---|---|---|
| Long Day Plants (LDP) | Wheat, Radish, Sugar beet, Barley | Flower when day length exceeds critical photoperiod. |
| Short Day Plants (SDP) | Tobacco, Chrysanthemum, Rice, Soyabean | Flower when day length is less than critical photoperiod. |
| Day Neutral Plants (DNP) | Tomato, Pepper, Cucumber, Sunflower, Maize | Flowering is independent of the duration of light. |
| Vernalisation Responders | Wheat, Barley, Rye, Carrot, Cabbage, Sugar beet | Cold-treatment triggers or accelerates flowering. |