Edexcel A (SNAB) A Level Biology:复习笔记4.2.6 Practical: Identifying Tissue Types Within Stems

• In order to identify tissue types within stems, a permanent pre-prepared slide could be used
• Alternatively, a section of a plant stem could be cut and stained before preparing a temporary slide

Apparatus

• Plant stem
• Scalpel
• Suitable stain
• Microscope slide
• Cover slip
• Forceps
• Dissecting needle
• Light microscope

Method

• Cut a very thin cross-section of the stem using a scalpel
• Carefully transfer each section into a dish containing a suitable stain and leave for one minute
  • A stain such as toluidine blue O (TBO) will make xylem and sclerenchyma fibres appear blue-green, while phloem will appear pinkish purple
• Rinse off each section in water and mount onto a microscope slide, before adding a cover slip (take care to lower the coverslip slowly over the sample from one side to the other to avoid trapping air bubbles, which can then be mistaken for plant tissues/structures)
• View under a microscope and adjust the focus to form a clear image
• Make a labelled drawing of the positions of the xylem vessels, phloem sieve tubes and sclerenchyma fibres

Light microscope image showing tissue types (sclerenchyma fibres, phloem sieve tubes and xylem vessels) found within plant stems and their locations relative to one another