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The pollen germination slide is one of the quickest experiments in Class 12 biology, and one of the easiest to get wrong. Too little pollen, the wrong flower or a dried-out drop and you see nothing. This post explains the method, why it works, how to count germination, and what examiners ask about it.
Where is this in the CBSE practical exam?
The CBSE Biology curriculum for 2026-27 lists "Prepare a temporary mount to observe pollen germination" as Class 12 experiment 1. Along with the onion root tip slide, it falls under slide preparation, marked out of 5 in the 30-mark practical. The spotting list also includes pollen germination on the stigma from a permanent slide or electron micrograph. Check your school's list for the current year.
What is the method?
NCERT's chapter on sexual reproduction in flowering plants gives it in two sentences. Dust pollen from flowers such as pea, chickpea, Crotalaria, balsam or Vinca onto a glass slide holding a drop of sugar solution of about 10 per cent. After about 15 to 30 minutes, look under the low-power lens. You are likely to see pollen tubes coming out of the pollen grains.
Step by step:
Make the solution. For 10 per cent (weight by volume), dissolve 10 g of sucrose and make it up to 100 mL with water. For a small batch, 2 g in 20 mL gives the same strength.
Pick fresh, open flowers whose anthers are shedding pollen.
Place one drop in the centre of a clean slide or cavity slide.
Tap the anthers over the drop so plenty of pollen falls in.
Wait 15 to 30 minutes, with the slide covered (for example, in a Petri dish with damp paper) so the drop does not dry.
Observe under low power, then high power for a closer look at the tubes.
Why does pollen germinate in sugar solution?
On a flower, compatible pollen germinates on the stigma and grows a pollen tube through one of its germ pores; NCERT describes the contents of the grain moving into the tube as it grows through the style towards the ovary. The sugar drop gives the grain water and a source of energy outside the flower. The germ pores are the gaps in the hard sporopollenin exine where the tube can emerge.
A classic study explains a puzzle many students meet. Brewbaker and Kwack (1963) found a "pollen population effect": small numbers of pollen grains grew poorly or not at all, under conditions where large populations grew well. They traced the effect to calcium ions and confirmed the result in 86 species from 39 plant families. Their own culture medium added boric acid, calcium nitrate, magnesium sulphate and potassium nitrate to 10% sucrose. For a school slide, plain sugar solution is the NCERT method; the practical lesson is to use plenty of pollen.
Worked example: germination percentage
These are sample numbers for practice, not real results. A student counts three fields of view:
Field 1: 40 grains, 26 with a pollen tube
Field 2: 35 grains, 21 with a tube
Field 3: 45 grains, 29 with a tube
Total grains = 40 + 35 + 45 = 120. Total germinated = 26 + 21 + 29 = 76.
Germination percentage = germinated / total × 100 = 76 / 120 × 100 ≈ 63.3%.
Decide in advance what counts as germinated, for example a tube at least as long as the grain is wide, and write that rule in your record so the count is consistent. Counting three or more fields also avoids picking the one field that looks most impressive.
Which viva questions should you prepare?
Why sugar? It supplies water and energy, standing in for the stigma.
Why does pollen viability matter? NCERT says it varies: in rice and wheat pollen loses viability within 30 minutes of release, while in some members of Rosaceae, Leguminosae and Solanaceae it lasts months. Use fresh pollen.
Where does the tube come out? Through a germ pore.
What happens next on a real flower? The tube grows through stigma and style to the ovule, enters a synergid and releases two male gametes.
Which mistakes cost marks?
Too little pollen, so nothing germinates.
Old or wilted flowers with pollen that has lost viability.
A drop that dries before you look. Keep the slide covered.
Looking too early. Give it the full 15 to 30 minutes.
No count in the record. A germination percentage shows you observed.
Only compatible pollen grows on a stigma; for why plants reject their own pollen, read outbreeding devices. For general viva tips, see board practical exams and viva questions. If you want help planning your practical revision, Fermi's AI tutor works out what you already know and builds a plan for the session.
A practice routine before the exam
Write the method from memory in six steps, with one reason for each.
Work out the germination percentage for the sample counts without looking.
Answer the four viva questions above aloud, in one sentence each.
If your school allows it, make one practice slide with pollen from a garden flower such as Vinca.
This week, find a flower that is shedding pollen near your home and note its name for your practical record.
