CORE PRACTICAL 7 :OBSERVE TS SECTIONS OF STEM, ROOT, LEAVES
Phloem
-Living tissue that translocate photosynthates -bidirectional movements
xylem
-has lignin= dead cells -transports water and minerals -direction = up the stem
collenchyma
-living cells -have additional cellulose to provide extra mechanical support -can stretch as plants grow and provides flexibility
why is toluidine blue O stain used
-metachromatic, reacts with different chemical components of cells to create a variety of colours
sclerenchyma
-thick lignified cell walls =dead cells -has an empty lumen -provides mechanical support
parenchyma
-unspecialised -provides packing around other tissues and support -can be modified for food storage and photosynthesis
procedure
1.Take the plant stem and place it on a white tile and fill a petri dish with a shallow level of distilled water and wet the razor to reduce friction while cutting thin transverse sections. (RA- make sure to hold stem firmly and cut away from self to avoid injury) 2. select thinnest section and place in on a slide and dub the specimens with paper towel to absorb any excess water 3.Put on the eye protection and gloves and use a pipette to add 2-3 drops of the Toluidine blue O stain to the specimen. Leave it to soak in for 3 minutes and add a cover slip then again use a paper towel to absorb any excess liquid. 4. on a light microscope turn objective sense to low power. -examine the slide by using a coarse focusing knob to lower and raise the stage until the image comes to focus -use the fine focusing knob to focus on the image further and draw and annotate an outline of the section as the miscroscope is still on low/meduim power
toluidine blue O stain with lignin and tennis colour
green -blue
toluidine blue O stain with pectins colour
pinkish purple
toluidine blue O stain with nucleic acid
purplish/greenish blue
why is too much stain bad?
satin will absorb too much light and it will be difficult to see any differences in structure
why are stains added to the stem and root cells?
thin sections do not absorb much light= difficult to see stain absorbs more light = easier to see
Cambium
unspecialised, gives rise to new phloem and xylem cells