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CSEEL shifts education from rote memorization to active inquiry and hands-on experimentation. Students observe, build, analyze, and apply scientific concepts to real-world challenges, developing critical thinking and scientific temper as envisioned by NEP 2020.

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Mitosis in Onion Root Tip Cells via Squash Method

Experiment video

What you will learn

Prepare temporary root tip squashes of Allium cepa to study and identify distinct stages of mitotic cell division (prophase, metaphase, anaphase, telophase).

Materials needed

Freshly germinated Onion Root Tips (1-2 cm long) fixed in Carnoy's fluid (1:3 acetic alcohol) vial
Freshly germinated Onion Root Tips (1-2 cm long) fixed in Carnoy's fluid (1:3 acetic alcohol) vial
₹50
What is it?
Acetocarmine 2% histological nuclear chromosome stain.
Specifications
Composition
2% carmine dye dissolved in 45% boiling acetic acid
pH
Acidic fixative-stain
Specific Target
Chromatin DNA and histone complexes
Bottle
100 mL dropper bottle
1N Hydrochloric Acid (HCl) mL
1N Hydrochloric Acid (HCl) mL
₹95
What is it?
Fresh Allium cepa (onion) root tips grown in aerated hydroponic culture.
Specifications
Harvest Time
10:00 – 11:30 AM (maximum mitotic activity)
Length
10 – 15 mm healthy white rootlets
Fixation
Carnoy's fluid (3:1 ethanol : glacial acetic acid)
Acetocarmine / Aceto-orcein Stain (2%) dropper bottle
Acetocarmine / Aceto-orcein Stain (2%) dropper bottle
₹140
What is it?
1.0 N Hydrochloric Acid (HCl) for pectinase-equivalent chemical maceration.
Specifications
Concentration
1.0 N standardized
Function
Dissolves calcium pectate middle lamella cement
Compound Research Microscope (100x oil immersion objective)
Compound Research Microscope (100x oil immersion objective)
₹185
What is it?
Standard laboratory apparatus used in Mitosis in Onion Root Tip Cells via Squash Method.
Specifications
Category
Biology Apparatus
Grade
CBSE / NEP 2020 Laboratory Standard
Spirit Lamp / Bunsen Burner & Test Tube Holder
Spirit Lamp / Bunsen Burner & Test Tube Holder
₹230
What is it?
Standard laboratory apparatus used in Mitosis in Onion Root Tip Cells via Squash Method.
Specifications
Category
Biology Apparatus
Grade
CBSE / NEP 2020 Laboratory Standard
Glass Slides, Coverslips, Razor Blade, and Dissecting Needle set
Glass Slides, Coverslips, Razor Blade, and Dissecting Needle set
₹275
What is it?
Standard laboratory apparatus used in Mitosis in Onion Root Tip Cells via Squash Method.
Specifications
Category
Biology Apparatus
Grade
CBSE / NEP 2020 Laboratory Standard
Blotting paper strips pack
Blotting paper strips pack
₹320
What is it?
Standard laboratory apparatus used in Mitosis in Onion Root Tip Cells via Squash Method.
Specifications
Category
Biology Apparatus
Grade
CBSE / NEP 2020 Laboratory Standard

Tick items as you collect them. Tap + to see the product, specifications and buy options.

Stay safe

Do not boil the root tips during acid hydrolysis or staining (boiling destroys chromosome morphology).
Apply thumb pressure strictly vertically during squashing; avoid sideways slipping which twists and shears cells.
Harvest root tips between 9:00 AM and 10:30 AM when mitotic index peaks in Allium cepa.
Use only the terminal 2 mm apical tip containing active dividing meristem.

Steps

0 of 7 steps done

1Cut 2-3 mm of the terminal actively growing apical meristem tip of the onion root.
Observation
Grow fresh root tips on onion bulbs in water; harvest terminal 2-3 mm root tips at 10:00 AM (peak mitotic window).
Safety
Fix root tips immediately in Carnoy's fixative (ethanol : glacial acetic acid 3:1) for at least 2 hours.
2Place root tips in a watch glass containing 1N HCl and warm gently over a spirit lamp for 2 minutes to hydrolyze the pectin middle lamella.
Observation
Hydrolyze fixed root tips in 1N HCl at 60°C for 5 minutes in a water bath to dissolve middle lamella pectin.
Safety
Control water bath temperature strictly at 60°C; over-hydrolysis destroys chromosome morphology.
3Discard acid, wash tips with water, and place on a clean glass slide.
Observation
Rinse root tips thoroughly in cold water; transfer to watch glass and add 2% Acetocarmine or Aceto-orcein stain.
Safety
Warm stain gently over spirit lamp without boiling to intensify DNA dye binding.
4Add 1 drop of 2% acetocarmine stain, warm gently over flame without boiling, and allow to stain for 5 minutes.
Observation
Cut and retain only the deeply stained terminal 1 mm meristematic tip on a clean glass slide.
Safety
Discard the non-dividing elongating root zone above 1 mm.
5Add a small drop of 45% acetic acid, place a coverslip over the tissue.
Observation
Place coverslip; apply firm, vertical thumb pressure through folded bibulous paper to squash cells into a single monolayer.
Safety
Squash strictly vertically; do not allow coverslip to slip sideways, which breaks chromosomes into debris.
6Cover the slide with a folded piece of blotting paper and press down firmly and vertically with the thumb to squash the meristem cells into a single monolayer.
Observation
Examine under 400× oil/high-dry magnification; tally cells across all four mitotic phases to calculate Mitotic Index.
Safety
Seal coverslip edges with clear nail polish if keeping slide for long-term study.
7Observe under low power (10x) to locate dividing zones, then switch to high power (40x and 100x) to document mitotic stages.

Tap + on a step to see what you will observe and any safety tips.

Record your observations

Mitotic Phase Observed	Chromosome Morphology & Location	Cell Count in Field	Phase Percentage (%)
Interphase	Chromatin diffuse, intact nuclear membrane, dark nucleolus	212 cells	84.8% (Resting/Replication)
Prophase	Chromatin condenses into distinct thick visible chromatid pairs	18 cells	7.2%
Metaphase	Chromosomes aligned strictly along equatorial metaphase plate	8 cells	3.2%
Anaphase	Sister chromatids separated, V-shaped moving to opposite poles	6 cells	2.4%
Telophase & Cytokinesis	Chromosomes at poles, nuclear membranes reform, cell plate forms	6 cells	2.4%

Tap a highlighted cell to write your own observation.

Result and conclusion

Distinct mitotic stages clearly observed: condensed chromosome threads (Prophase), equatorial plate alignment (Metaphase), sister chromatid poleward separation (Anaphase), and nuclear reorganization (Telophase).

Mitotic Index (%) = (Number of cells in mitosis / Total number of cells observed) × 100 = (38 / 250) × 100 = 15.2%

Observation	What it means
Meristematic Mitotic Activity	Onion root tips contain active apical meristem where cells divide rapidly to facilitate root elongation.
Interphase Dominance	Over 84% of cells are in interphase, demonstrating that DNA replication and cell growth occupy the vast majority of cell cycle duration.
Equatorial Metaphase Alignment	Metaphase shows classic equatorial plate alignment with centromeres attached to spindle fibers.
V-Shaped Anaphase Centromeres	Metacentric chromosomes pull toward poles with centromeres leading, assuming characteristic V and J shapes.

Cell Cycle Phase Distribution in Meristematic Root Tip Cells

Sample readings. Replace with your own results.

Experiment photos

Before the experimentDuring the experimentResult