Xylem, phloem and sclerenchymaEdexcel International A Level Biology: Mind map

Exam questions on Xylem, phloem and sclerenchyma

1. A student examines a stained transverse section of a young sunflower stem using a light microscope. The vascular bundles form a ring near the outside of the stem, and each bundle contains xylem, phloem and a cap of sclerenchyma fibres.
   Describe two differences in structure between a xylem vessel and a phloem sieve tube element.2 marks
2. A student prepares temporary slides of sections cut from the root, stem and leaf of a plant to compare the tissues. The sections are stained with toluidine blue, which stains lignified walls blue-green and unlignified cellulose walls pink or purple. The student wants to identify the tissues and to measure their dimensions.
   Describe two steps the student should take to make a temporary slide of a stem section that is suitable for identifying the tissues.2 marks
3. A teacher describes three types of cell from a plant stem. Cell P is long and dead, with a very narrow lumen and thick lignified walls. Cell Q is a dead, hollow tube with a wide lumen, lignified walls with small pits, and no end walls between neighbouring cells. Cell R is a living cell with thin cellulose walls, perforated end walls and almost no cytoplasm, and it lies next to a cell with dense cytoplasm.
   Identify cells P, Q and R and state one main function of each.3 marks