core practical 7 use a light microscope to : make observations i.transverse sections of roots, stems, leaves ii.plant tissues iii. identify sclerenchyma fibres ,phloem sieve tubes ,xylem vessels and their location

procedure on making observations of tranverse sections of roots

1.collect a piece of plant stem.Add drops f water to centre of white tile and wet razor to reduce friction.Hold plant stem and cut several transverse sections across the stem,keeping them thin 2.select thinnest section and place it on a slide.add a drop of water. and remove excess water using absorbent paper 3.add tolouidine blue O stain and ;eave for 2-4 mins. then add a coverslip and gently remove excess stain with a paper towel 4.turn objective lens to low power.focus using course knob ,moving the lens away from the stage to avoid damage to slide and lens 5.dram and annotate section.show arrangement of tissues within the stem 6.repeat 1-5 using root. 7.to make leaf cross section,place lead bw 2 thin pieces of polysterene.gently stroke razor blade across top leaf and polysterene to shave off 4/5 thin sections 8.place on glass slideand cover w cover slip

safety need

1.wear eye protection 2.avoid skin contact with toloidine blue stain 3.take care using razor blades and mounted needles 4.if using microscope w daylight illumniation-avoid contact with direct sunlight

Why is toluidene stain used

it's a metachromatic stain,which means it reacts w diff chemical properties of cells to prod diff variety of colours.this can provide the nature of the cell.tolouidine blue o stain lignin and tannins green to blur,pectins pinkish purple and nucleic acids purpluish or bluish green

suggest why a stain was used on the stem and root cells

sections of stem and root do not absorb much light tf diff to see using a light microscope.stain absorbs more light tf easier to see structures

describe a method for comparing size of the xylem tissue in the root and stem samples

use a micrometer slide and eyepiece graticule.thhe graticule is calibrated using the micrometer slide.size of the xylem tissue can be calc and compared

explain why it was important not to use too much stain when preparing the slide

will be diff to see anything using the microscope.any diff bw the cells will ass hidden as the stain ill absorb all the light