SSC CGL Biology · Plant Biology
Plant Form and Processes
Leaf venation and arrangement with example plants, xylem and phloem, how stomata open, transpiration, plant nutrients and plant hormones.
Why this matters
Eleven questions in the bank: one from the 2023 shifts, six from the 2024 shifts and four from the 2025 shifts. Most name a plant and ask its leaf type, or state a process and ask whether it is true, so the example plants are worth learning.
Concept 1 of 2: Leaves, tissues and plant form
Definition
Leaves:
- Venation: reticulate (net) in dicots such as tulsi, coriander, China rose; parallel in monocots such as maize. Parallel veins give vascular bundles of similar size.
- Phyllotaxy (leaf arrangement): opposite in guava and Calotropis; alternate in China rose and mustard; whorled in Alstonia.
- Compound leaves: pinnate in neem (leaflets along an axis); palmate in silk cotton (leaflets from one point).
Tissues and form:
- Xylem carries water; phloem carries food.
- A plant's habit is its growth form: size, shape, orientation. Its habitat is where it lives.
- Red algae reproduce vegetatively by fragmentation; grafting and cutting are methods people use.
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 1 · Plant Biology · Plant Form and Processes
Habit is not habitat
Concept 2 of 2: Stomata, transpiration, nutrients and hormones
Definition
Water:
- When water flows into the guard cells they swell and the stoma opens; when they lose water it closes.
- Transpiration is fastest in dry, windy weather. Its pull lifts sap by cohesion-tension. It causes wilting only when loss exceeds uptake, not always.
Nutrients: macronutrients (in bulk) include calcium; micronutrients (in traces) include boron, zinc and iron.
Hormones: auxins promote growth; gibberellins lengthen stems; cytokinins delay ageing; ethylene ripens fruit.
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 2 · Plant Biology · Plant Form and Processes
Transpiration does not always wilt a plant
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Watch out for (2)
- Habit is not habitat→ Leaves, tissues and plant form
- Transpiration does not always wilt a plant→ Stomata, transpiration, nutrients and hormones
Test yourself on a real paper
Sit a past SSC CGL paper, timed and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.