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Plant anatomy – T.S. of dicot and monocot roots and stems

BiologyPlant PhysiologyAges 16–17Virtual lab

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Use with my class

A virtual practical: cut thin transverse sections of sunflower and maize stems and roots, stain them with safranin, wash, mount in glycerine and view them at ×4, ×10 and ×40. Label the epidermis, cortex, endodermis with Casparian strips, pericycle, xylem, phloem and cambium, compare a ring of bundles with scattered bundles and a few xylem arms with many, and measure a vessel with the eyepiece graticule.

Lesson: Anatomy of roots and stems; preparing transverse sections

What it shows

This practical builds real-looking transverse sections cell by cell. A young sunflower stem shows a ring of open collateral bundles, each with a sclerenchyma cap, phloem, cambium and endarch xylem, around a large pith. A maize stem has many closed bundles scattered in ground tissue, each with a fibre sheath, two large metaxylem vessels and a water-filled lacuna. Roots have radial bundles with exarch xylem: two to four arms in the dicot root, many arms and a pith in maize. Safranin stains lignified walls red. Section thickness, staining time and bubbles change the image qualitatively.

How to use

In Prepare, press Cut section a few times, tap the thinnest section, then press Stain and Take out after one to three minutes, Wash and Mount. In Microscope, start with ×4, focus with Coarse focus and Fine focus, then use Label to place tissue names and Measure to drag the ruler. Support shows wilting and annual rings.

Parameters you can change

  • Screen Prepare a slide, Microscope, Support and annual rings
  • Specimen Dicot stem (sunflower), Monocot stem (maize), Dicot root (sunflower), Monocot root (maize), Unknown section
  • Xylem arms in the dicot root 2–4
  • Objective ×4, ×10, ×40
  • Water lost by the plant 0–40 %
  • Years of secondary growth 0–8

Questions to explore

  1. How can you tell a ring of open bundles from scattered closed bundles under low power?
  2. Why does a section that is too thick look dark and blurred at ×40?
  3. Why do the Casparian strips stain red with safranin while the cortex stays pale?

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