Microscopic evaluation of crude drugs is an essential practical skill for B.Pharm students, linking pharmacognosy, plant anatomy, and quality control. This concise guide emphasizes microscopy principles — maceration, staining, powder microscopy, sectioning (transverse/longitudinal), and recognition of tissue elements such as trichomes, vessels, fibres, stomata, crystals, starch grains, secretory structures and sclereids. It also covers common mounts, staining reagents (phloroglucinol, iodine, safranin), polarized-light observation, and identification of adulteration or foreign matter. Mastery of these topics enhances accurate identification, pharmacopoeial compliance, and laboratory reporting. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary purpose of microscopic evaluation of crude drugs?
- To determine the chemical potency of a drug by chromatography
- To identify diagnostic anatomical features and detect adulteration
- To estimate oral bioavailability in humans
- To measure pH and solubility of plant extracts
Correct Answer: To identify diagnostic anatomical features and detect adulteration
Q2. Which of the following microscopic features is most diagnostic for identifying many powdered plant drugs?
- Color of the powder
- Presence and type of trichomes
- Odor emitted on rubbing
- Solubility in water
Correct Answer: Presence and type of trichomes
Q3. Which reagent is commonly used to detect starch grains in crude drug sections?
- Phloroglucinol-HCl
- Iodine (Lugol’s solution)
- Sulfovanillin
- Dragendorff’s reagent
Correct Answer: Iodine (Lugol’s solution)
Q4. Phloroglucinol-HCl is used in microscopic evaluation to indicate the presence of:
- Starch grains
- Lignified cell walls (lignin)
- Fixed oil droplets
- Calcium carbonate
Correct Answer: Lignified cell walls (lignin)
Q5. Which microscopic technique enhances visualization of crystalline inclusions and starch extinction crosses?
- Fluorescence microscopy
- Phase-contrast microscopy
- Polarized light microscopy
- Electron microscopy
Correct Answer: Polarized light microscopy
Q6. Raphides and druses are types of which diagnostic feature seen in crude drugs?
- Secretory ducts
- Calcium oxalate crystals
- Glandular trichomes
- Lignified fibers
Correct Answer: Calcium oxalate crystals
Q7. Which plant tissue element provides mechanical support and is commonly identified in powdered drugs as long, thick-walled cells?
- Parenchyma cells
- Sclerenchyma fibers
- Collenchyma cells
- Secretory vesicles
Correct Answer: Sclerenchyma fibers
Q8. A common clearing agent used to render plant sections transparent for microscopy is:
- Chloral hydrate
- Sulfuric acid
- Acetone
- Phenol
Correct Answer: Chloral hydrate
Q9. In powder microscopy, which feature helps distinguish true cinnamon from cassia?
- Type of stomata
- Presence and shape of stone cells and vessels
- Color under visible light
- Solubility in ethanol
Correct Answer: Presence and shape of stone cells and vessels
Q10. Which staining reagent imparts red coloration to lignified cell walls?
- Safranin
- Iodine
- Neutral red
- Methylene blue
Correct Answer: Safranin
Q11. The stomatal index is useful to characterize leaf drugs because it:
- Measures the size of epidermal cells only
- Is the ratio of stomata to total epidermal cells, independent of leaf size
- Indicates the chlorophyll content of the leaf
- Estimates moisture content of the crude drug
Correct Answer: Is the ratio of stomata to total epidermal cells, independent of leaf size
Q12. Which of the following is an idioblast commonly used as a diagnostic character in many crude drugs?
- Trichome
- Parenchyma mass
- Calcium oxalate crystal-containing cell
- Vascular cambium
Correct Answer: Calcium oxalate crystal-containing cell
Q13. Which microscopic observation suggests the presence of secretory canals or ducts in a drug sample?
- Regularly arranged palisade cells
- Elongated tubular cavities lined by secretory epithelium
- Numerous stomata on both leaf surfaces
- Clustered fibres with thick walls
Correct Answer: Elongated tubular cavities lined by secretory epithelium
Q14. Which method is most suitable to separate individual cells or fibres for identification?
- Maceration with dilute alkali (e.g., NaOH)
- Direct mounting without treatment
- Heating with concentrated acid
- Mixing with glycerin only
Correct Answer: Maceration with dilute alkali (e.g., NaOH)
Q15. Presence of abundant unicellular or multicellular glandular trichomes in a powdered sample most strongly indicates:
- High lignin content
- Possible aromatic oil-bearing drug
- Root origin only
- Absence of secretory substances
Correct Answer: Possible aromatic oil-bearing drug
Q16. Which microscopic feature differentiates fibres from vessels in a powder mount?
- Fibres show bordered pits while vessels do not
- Vessels are tubular with perforation plates; fibres are elongated narrow cells with thick walls
- Fibres contain chloroplasts; vessels do not
- Vessels are always shorter than fibres
Correct Answer: Vessels are tubular with perforation plates; fibres are elongated narrow cells with thick walls
Q17. Which diagnostic crystal type appears as needle-like bundles under the microscope?
- Druses
- Cystoliths
- Raphides
- Prismatic crystals
Correct Answer: Raphides
Q18. During microscopic authentication of a drug, foreign matter such as sand is identified by observing:
- Transparent, angular mineral particles lacking cellular structure
- Elongated lignified cells
- Glandular trichomes with secretions
- Starch grains with extinction cross
Correct Answer: Transparent, angular mineral particles lacking cellular structure
Q19. Which objective is typically used first when locating features on a microscope slide of a crude drug section?
- 100x oil immersion objective
- 40x (high power) objective
- 10x (low power) objective
- 0.5x macro objective
Correct Answer: 10x (low power) objective
Q20. Which powder microscopy characteristic helps detect adulteration by substitution with cheaper plant material?
- Presence of typical diagnostic cells and absence of expected diagnostic elements
- Color measured by spectrophotometer
- Tablet hardness
- Melting point
Correct Answer: Presence of typical diagnostic cells and absence of expected diagnostic elements
Q21. Which microscopic sign indicates a high content of essential oil in a plant drug?
- Numerous calcium oxalate druses
- Abundant oil cells or oil ducts containing refractive droplets
- Large sclerenchyma bundles
- Thick cuticle with no cavities
Correct Answer: Abundant oil cells or oil ducts containing refractive droplets
Q22. In slide preparation, glycerin is often used as a mounting medium because it:
- Evaporates quickly leaving dry mount
- Preserves and provides refractive index suitable for plant cells
- Stains lignified walls red
- Cleaves cell walls for maceration
Correct Answer: Preserves and provides refractive index suitable for plant cells
Q23. Which anatomical section plane is most appropriate to study vascular bundles arrangement in stems?
- Longitudinal section
- Transverse (cross) section
- Tangential section
- Oblique smear
Correct Answer: Transverse (cross) section
Q24. Which of the following artifacts can be introduced during slide preparation and confuse diagnosis?
- Air bubbles and broken tissues
- Actual secretory cavities
- Calcium oxalate crystals naturally present
- Starch grains from the plant
Correct Answer: Air bubbles and broken tissues
Q25. Which cell type is most likely to contain tannin deposits visible microscopically as dark granular contents?
- Collenchyma cells
- Tanniniferous idioblasts (parenchyma with tannin)
- Sieve elements
- Guard cells
Correct Answer: Tanniniferous idioblasts (parenchyma with tannin)
Q26. Polarizing microscopy shows strong birefringence for which component commonly seen in seeds and tubers?
- Cellulose microfibrils only
- Starch grains with extinction cross
- Protein bodies without structure
- Oil droplets
Correct Answer: Starch grains with extinction cross
Q27. Which microscopic sign is typical of bark drugs from woody plants?
- Presence of periderm, secondary phloem, and cork cells
- High number of stomata on outer surface
- Abundant palisade parenchyma
- Large central pith with simple vessels
Correct Answer: Presence of periderm, secondary phloem, and cork cells
Q28. During microscopic authentication, the term “pollen grains” as a diagnostic feature refers to:
- Nuclei within xylem vessels
- Characteristic coated reproductive units often resistant to digestion and useful for identification
- Secretory resin ducts
- Broken epidermal cells
Correct Answer: Characteristic coated reproductive units often resistant to digestion and useful for identification
Q29. Which microscopic observation would point to oil-resin content in a gum-resin drug?
- Numerous large sclereids
- Refractive vesicles or globules that may fuse on crushing
- Clear lamellar cellulose patterns
- Abundant stomatal complexes
Correct Answer: Refractive vesicles or globules that may fuse on crushing
Q30. What is the advantage of using reference slides and photomicrographs in microscopic evaluation?
- They replace the need for trained personnel
- They provide comparative standards to confirm identity and diagnostic features
- They guarantee chemical potency
- They increase the pharmacological activity of samples
Correct Answer: They provide comparative standards to confirm identity and diagnostic features
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
Mail- Sachin@pharmacyfreak.com