CP6 write up - Identify sclerenchyma fibres, phloem sieve tubes and xylem vessels
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Course
Core Practicals
Institution
PEARSON (PEARSON)
Edexcel A Biology A level core practical Write ups. All include an introduction, hypothesis, variables, method, results, evaluations...
CP6 -Identify sclerenchyma fibres, phloem sieve tubes and xylem vessels and their location within stems through a light microscope
Core Practical 6 - identifying sclerenchyma fibres, phloem sieve tubes and xylem vessels
and their location within stems through a light microscope
Aim:
- To look at the structure of xylem vessels, phloem sieve tubes and sclerenchyma
fibres
- Locate the position of these tissues within the stem
- To develop practical skills
Introduction: The main purpose of plant stems is to carry substances between different
parts of the plant. Xylem and phloem are the two types of transport system found in plant
stems, transporting water and minerals in the case of xylem, and sugars and amino acids in
phloem. In plant stems, the xylem and phloem tissues are organised together in groups
known as vascular bundles.
Hypothesis: The xylem will have a thicker cell wall and a bigger diameter than the phloem
as it is covered in lignin. There will also be a cambium separating the xylem and the phloem.
Variables:
- The size of the tinned rhubarb (if the specimen is too bit, the vascular bundles cannot
be effectively observed, so all specimens should be weighed to ensure they are
roughly the same weight, and therefore size)
- The amount of stain that remains on the specimen after the filter paper absorbs the
excess (too much or too little stain could make the specimen blurry, or make it
difficult to accurately compare the sizes of the phloem and xylem, so the mass
difference before and after adding the stain and removing excess should be recorded
and kept constant)
- The amount of glycerol that remains on the specimen after excess has been blotted
off (once again, too much or too little could make it hard to see properly and obtain
accurate results, and therefore the mass difference should be recorded and kept
constant)
Safety:
hazard Measure
Methyl blue stains Avoid contact with skin and clothes
Sharp mounted needles Tease the bundles carefully away from you
If liquid comes in contact with skin Flood area of skin with water and wash
thoroughly
Dangers of microscope mirrors and light Ensure the microscope is placed away from
direct sunlight
Harmful substances Wear protection, lab coats and disposable
gloves
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