Biology Plant Biology
Key Concepts & Formulas
Provide 5-7 essential concepts for Biology Plant Biology:
| # | Concept | Quick Explanation |
|---|---|---|
| 1 | Photosynthesis Formula | 6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂ (occurs in chloroplasts) |
| 2 | Plant Tissue Types | Meristematic (growth) vs Permanent (specialized) tissues; Xylem transports water upward, Phloem transports food downward |
| 3 | Phototropism | Growth towards light; caused by uneven distribution of auxin hormone; stem bends toward light source |
| 4 | Nitrogen Fixation | Conversion of atmospheric N₂ to usable ammonia by Rhizobium bacteria in legume root nodules |
| 5 | Transpiration Rate Formula | Rate = (Initial weight - Final weight) / Time; measured in g/hour through potometer |
| 6 | Plant Cell Structure | Unique features: Cell wall (cellulose), large vacuole, chloroplasts; absence of centrioles |
| 7 | Respiration vs Photosynthesis | Opposite processes: Respiration uses O₂ releases CO₂ (24 hours); Photosynthesis uses CO₂ releases O₂ (daytime only) |
10 Practice MCQs
Q1. Which part of the plant contains chloroplasts for photosynthesis? A) Root hairs B) Leaf mesophyll cells C) Xylem vessels D) Root cortex cells
Answer: B) Leaf mesophyll cells
Solution:
- Chloroplasts are concentrated in palisade mesophyll cells (50-100 per cell)
- These cells are positioned just below upper epidermis for maximum light absorption
- Root cells lack chloroplasts as they don’t receive light underground
Shortcut: “Chloroplasts need light → find cells that receive most light → upper leaf surface”
Concept: Biology Plant Biology - Photosynthesis location
Q2. The process where water moves from roots to leaves against gravity is called: A) Transpiration B) Guttation C) Osmosis D) Root pressure
Answer: A) Transpiration
Solution:
- Transpiration creates pull (transpiration pull) from leaf surface
- Cohesion-tension theory: water molecules stick together (cohesion) and are pulled upward
- Rate: 15-45 m/hour in tall trees
Shortcut: “Transpiration = Transportation upward; starts with ‘T’ = ‘Top’ pull”
Concept: Biology Plant Biology - Water transport mechanism
Q3. Which hormone causes seed dormancy? A) Auxin B) Gibberellin C) Abscisic acid D) Cytokinin
Answer: C) Abscisic acid
Solution:
- Abscisic acid (ABA) concentration: 10-50 μg/g dry weight in dormant seeds
- Prevents premature germination; breaks down with water/scarification
- Also causes stomatal closure during drought
Shortcut: “ABA = Anti-Breaking-Active; stops germination”
Concept: Biology Plant Biology - Plant hormones
Q4. A plant loses 50g water in 5 hours through transpiration. If leaf surface area is 100 cm², calculate transpiration rate per cm²/hour. A) 0.1 g/cm²/hr B) 0.5 g/cm²/hr C) 1.0 g/cm²/hr D) 2.5 g/cm²/hr
Answer: A) 0.1 g/cm²/hr
Solution:
- Total transpiration = 50g/5 hours = 10g/hour
- Rate per cm² = 10g/hour ÷ 100 cm² = 0.1 g/cm²/hour
- Normal range: 0.05-0.2 g/cm²/hour for most plants
Shortcut: “Divide total by both time and area: 50÷5÷100 = 0.1”
Concept: Biology Plant Biology - Transpiration calculation
Q5. In a C3 plant, how many ATP molecules are required to fix one CO2 molecule? A) 1 B) 2 C) 3 D) 4
Answer: C) 3
Solution:
- Calvin cycle requires: 3 ATP + 2 NADPH per CO2
- Breakdown: 2 ATP for phosphorylation, 1 ATP for regeneration
- Total for glucose (6CO2): 18 ATP + 12 NADPH
Shortcut: “3 ATP = ‘Tri’carbon fixation needs ’tri’ ATP”
Concept: Biology Plant Biology - Photosynthesis energy requirements
Q6. A station gardener observes guttation drops on grass at 5 AM. This occurs through: A) Stomata B) Lenticels C) Hydathodes D) Cuticle
Answer: C) Hydathodes
Solution:
- Guttation: water droplets from leaf margins (100-200 droplets/cm²)
- Occurs when transpiration is low (high humidity, night) and root pressure is high
- Hydathodes present at vein endings in grass (200-500 per leaf)
Shortcut: “Gutta-tion = Gutter-like drops → need special ‘holes’ = Hydathodes”
Concept: Biology Plant Biology - Water loss mechanisms
Q7. If a train’s pantry car stores 500 kg potatoes, how much CO2 do they release daily through respiration at 25°C? (Assume 1 kg potatoes release 0.4g CO₂/day) A) 100g B) 200g C) 400g D) 500g
Answer: B) 200g
Solution:
- CO₂ release = 500 kg × 0.4g/kg = 200g/day
- Respiration rate doubles every 10°C rise (Q10=2)
- At 25°C, rate is 2.5× faster than at 5°C
Shortcut: “500 × 0.4 = move decimal: 50 × 4 = 200”
Concept: Biology Plant Biology - Plant respiration rates
Q8. A 20m railway platform tree shows annual rings: 12 rings in 6cm radius. Calculate average yearly radial growth. A) 0.25 cm/year B) 0.5 cm/year C) 1 cm/year D) 2 cm/year
Answer: B) 0.5 cm/year
Solution:
- 1 ring = 1 year growth (in temperate climates)
- Total growth = 6 cm over 12 years
- Average = 6 cm ÷ 12 years = 0.5 cm/year
- Secondary growth occurs in vascular cambium
Shortcut: “Growth per year = total ÷ rings: 6÷12 = 0.5”
Concept: Biology Plant Biology - Secondary growth calculation
Q9. In a greenhouse at 30°C, C3 plant photosynthesis rate is 15 mg CO₂/dm²/hour. If temperature drops to 20°C, what’s the new rate? (Q10 for photosynthesis = 2) A) 3.75 mg B) 7.5 mg C) 30 mg D) 60 mg
Answer: B) 7.5 mg
Solution:
- Temperature coefficient Q10 = 2 means rate halves every 10°C drop
- 30°C → 20°C = 10°C drop
- New rate = 15 ÷ 2 = 7.5 mg CO₂/dm²/hour
Shortcut: “Q10=2: every 10°C drop = half rate”
Concept: Biology Plant Biology - Temperature effects on photosynthesis
Q10. A train carries 1000 quintals wheat. If 2% by weight is lost to respiration during 10-day journey at 35°C, calculate total CO₂ produced. (Respiratory quotient = 1, wheat CHO composition) A) 2 quintals B) 20 quintals C) 200 kg D) 2000 kg
Answer: A) 2 quintals
Solution:
- 2% of 1000 quintals = 0.02 × 1000 = 20 quintals wheat lost
- RQ = 1: 1g CHO → 1g CO₂ produced
- CO₂ produced = 20 quintals = 2 metric tons
Shortcut: “2% loss = 2% CO₂ produced from original”
Concept: Biology Plant Biology - Respiratory losses calculation
5 Previous Year Questions
PYQ 1. The green pigment essential for photosynthesis is: [RRB NTPC 2021 CBT-1]
Answer: Chlorophyll
Solution:
- Chlorophyll a: C₅₅H₇₂MgN₄O₅ (primary pigment)
- Absorbs red (660nm) and blue-violet (430nm) light
- 1g chlorophyll can fix 100g CO₂/hour in optimal conditions
Exam Tip: Remember “Chloro” = green, “phyll” = leaf; always associated with light reactions
PYQ 2. Which tissue transports food from leaves to roots? [RRB Group D 2022]
Answer: Phloem
Solution:
- Phloem sap velocity: 0.3-1.5 m/hour
- Transports sucrose (10-30% concentration)
- Companion cells provide energy for active transport
- Direction: source (leaves) → sink (roots/storage)
Exam Tip: “Phloem = Food transport; flows ‘down’ but can go up to fruits”
PYQ 3. Calculate water potential if solute potential = -8 bars and pressure potential = +3 bars. [RRB ALP 2018]
Answer: -5 bars
Solution:
- Water potential (Ψ) = Solute potential (Ψs) + Pressure potential (Ψp)
- Ψ = -8 bars + 3 bars = -5 bars
- Negative indicates water will move in (higher to lower potential)
Exam Tip: Always add: solute (usually negative) + pressure (usually positive)
PYQ 4. A station nursery has 200 plants. If each plant transpires 500ml/day, calculate total water loss per week. [RRB JE 2019]
Answer: 700 liters
Solution:
- Daily loss = 200 × 500ml = 100,000ml = 100 liters
- Weekly loss = 100 × 7 = 700 liters
- Average mature plant: 200-1000ml/day depending on species
Exam Tip: Convert ml to liters at end: 1000ml = 1 liter
PYQ 5. Which mineral deficiency causes yellowing between leaf veins? [RPF SI 2019]
Answer: Iron
Solution:
- Iron deficiency: Interveinal chlorosis (green veins, yellow tissue)
- Iron needed for chlorophyll synthesis (0.1-0.5% dry weight)
- Common in alkaline soils (pH >7) where iron becomes unavailable
Exam Tip: “Iron = Interveinal symptoms; Magnesium = Overall yellowing”
Speed Tricks & Shortcuts
For Biology Plant Biology, provide exam-tested shortcuts:
| Situation | Shortcut | Example |
|---|---|---|
| C3 vs C4 plants | “C3 = Cool climates, 3-carbon first product; C4 = Calid climates, 4-carbon” | Wheat (C3) vs Maize (C4) |
| Xylem vs Phloem | “Xylem = X-axis upward; Phloem = Food flows ‘down’ primarily” | Water up xylem, sugar down phloem to roots |
| Photosynthesis equation | “6-6-6 rule: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂” | Balance: 6 carbons each side |
| Plant hormones | “GAS: Gibberellin = Growth, ABA = Anti-growth, SA = Stress response” | GA for bolting, ABA for dormancy |
| Mineral deficiencies | “NPK = Necrosis (N), Purple (P), Kinked leaves (K)” | N: yellowing, P: purple stems, K: leaf curl |
Common Mistakes to Avoid
| Mistake | Why Students Make It | Correct Approach |
|---|---|---|
| Confusing transpiration with guttation | Both involve water loss | Transpiration = vapor through stomata (day); Guttation = liquid through hydathodes (night) |
| Reversing xylem/phloem transport | Similar sounding names | Xylem = Water up; Phloem = Food down (mnemonic: XY=up axis) |
| Forgetting temperature effects | Assume constant rates | Photosynthesis decreases >35°C; Respiration increases with temperature |
| Misidentifying plant tissues | Focus only on function | Always check: location (center vs outer), cell type (living vs dead), direction |
| Overlooking RQ values | Assume CO₂ always equals O₂ | RQ=1 for carbs, <1 for fats, >1 for proteins |
Quick Revision Flashcards
| Front (Question/Term) | Back (Answer) |
|---|---|
| Photosynthesis light reactions location | Thylakoid membranes in chloroplasts |
| CAM plants temporal separation | Open stomata at night, closed daytime |
| Annual ring formation | Spring wood (wide vessels) vs Autumn wood (narrow) |
| Root pressure value | 1-2 atmospheres (can push water up 10-20 feet) |
| Chlorophyll absorption peaks | Red (660nm) and Blue (430nm) |
| C4 plants first CO₂ acceptor | PEP (Phosphoenolpyruvate) in mesophyll |
| Leghemoglobin function | O₂ scavenger in root nodules (protects nitrogenase) |
| Vernalization requirement | Cold treatment (0-5°C for 30-60 days) for flowering |
| Critical day length for wheat | Long day plant (>14 hours daylight needed) |
| Water transport velocity | 15-45 m/hour in xylem vessels |
Topic Connections
How Biology Plant Biology connects to other RRB exam topics:
- Direct Link: Chemistry - Photosynthesis involves redox reactions (CO₂ reduction, H₂O oxidation)
- Combined Questions: Physics - Light absorption spectra, pressure calculations in xylem
- Foundation For: Environmental Science - Carbon cycle, oxygen production, deforestation impacts
- Math Applications: Calculating growth rates, transpiration ratios, photosynthetic efficiency
- Current Affairs: GM crops, organic farming, carbon sequestration by railways
BETA
