Topic 4 Core Practicals

Question 1

CP6 method

Answer 1

• use sharp scalpel to cut out piece of stem
• cut thin transverse sections across it using a moistened new razor blade
• cut lots of sections, and use a paintbrush to transfer sections to a watch glass of water
• transfer thinnest sections to a slide and add a few drops of Toluidine blue
• cover with coverslip
• place pre-prepared slide under microscope
• calibrate eyepiece graticule using stage micrometer
• use eyepiece graticule to measure and compare mean diameter of 3 xylem vessels and 3 phloem sieve tubes
• draw low-power plan drawing
• label position of vascular bundles

Question 2

CP7 method

Answer 2

• use measuring cylinder to fill tube with ‘all nutrients’ solution
• cover top of tube in foil, pushing down on covering to create ‘well’ in centre
• leave small hole in the foil for plant stem
• push plantlet roots through hole so it is in the solution below
• measure length of plantlet from rim of test tube and record
• repeat steps using other solutions
• wrap tubes in aluminium foil and place in holder
• place rubes under sunny windowsill
• top up solutions as necessary

Question 3

CP8 method

Answer 3

• set up two clamp and stands and boss clamps
• measure thickness and length of fibre using micrometer and metre ruler
• attach ends of fibres to each clamp so that fibre is stretched horizontally between the stands
• place bubble wrap underneath fibre
• place empty weight hook on fibre
• gradually add weights, first at 100g then at 10g intervals until fibre breaks
• record number of masses and final mass endured before falling
• repeat for other fibre(s)

Question 4

CP8 control variables

Answer 4

• tautness of fibre - make sure fibre is parallel with ground and held straight
• size of mass at each addition - add 10g at a time using same set of masses
• length of fibre - measure using metre ruler and adjust distance of clamp and stands accordingly