As Biology- Core Practicals Topics 3&4

Observing Mitosis

Totipotency and Tissue Culture

The Strength of Plant Fibres

Investigating Plant mineral Dificiencies

Effect of Garlic and Mint on Bacterial growth

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Observing Mitosis

Chromosomes stained blue using orcein ethanoicstain.

Equipment: 

  • Garlic root
  • sharp knife
  • 1M hydrochlosic acid
  • Ethanoic acid
  • Orcein ethanoic stain
  • Ice cold distiled water
  • water bath at 60*C
  • Two watch glasses
  • test tuebs
  • 2 pipets
  • microscope slides
  • forceps mounted needle 
  • filter paper 
  • microscope 
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Observing Mitosis

Method:

Cut the Meristem (the area were mitosis occurs) of the garlic root. Place it on to the microscope slide. Add the HCL to soften the cellulose cell wall, in particular the pectin made of cellulose microfibrils and calcium. Add the Acetic Oricein stain so that the chromosomes can be seen. Pass it through a flame to condense the stain. the pice will need to be macerated using a needle and placing a cover slip over so it becomes one cell thick, and can there for be seen easily. Put under microscope and observe.

Calculations:

  • Percentage of cells in each stage of mitosis
  • Mitotic index: muber of cells containing visable chromosomes/ total number of cells in field of view

Issues:

  • Resolution of microscope. 
  • Human error in counting cells. 
  • Enough time in the solishons to enable successful maceration or staining.
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Toitpotency and Tissue Culture

Equipment:

  • Seeds of white mustards 
  • Agar
  • Distilled water
  • Damp sponge 
  • Cling film
  • McCartney bottles
  • Weighing scales
  • Plastic tray 
  • 250ml beaker 
  • Glass rod
  • Scissors
  • Sunny windowsill.
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Toitpotency and Tissue Culture

Method: 

Allow seeded to germinate on damp cloth. Make up agar solution mixed with plant hormones. Do at lest 3 repeats. Push the plant in to the agar solution and cover. leave to germinate for 1 week. Oberve if the plant has grown any leaves, roots (if it was totipotent).

Out come:

  • Explant grows root and leaves continue to grow. You need to be able to exsplane why they are coverd in cling film and when they continue to grow even when coverd, also why they shouldnt be opend again.

Issues: 

  • Unwanted pathogens growing in gel as it is a good source of water and nutrients
  • wrong part of plant cut an inserted in to plant.
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The Tensile Strength of Plant Fibres

Equipment:

  • stems of stinging nettles or Celery
  • bucket
  • gluves
  • paper towels
  • clamp stand
  • slotted mass and holders
  • white tile
  • sharp knife

Variables 

  • Length of plant fiber
  • size of each individual mass
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The Tensile Strength of Plant Fibres

Method

Leave plants in a bucket of water for atleast a week, so the plant fibers can be easily exstracted, or with the celery leave in coloured water so fibers can be easilty seen. Pull out fibers. Conect fibers between two clamp stands and gradualy add mass untill the fiber snapas. Try with indivudual fibers from diffrent plants, try diffrent ways of combineing fibers eg twists and plats.

Out come:

The more fibers connected to gether the more mass is can take.

Evaluation issues:

  • Maintaining length of fibers
  • ensuring consistency when when twisting or plating
  • using fibers of the same age (they become more britle with age)
  • Exstracting the whole fiber that are usefull
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Investigating plant mineral deficiencies

Independent variable: Minerals presant

Dependent variable: Physical characteristics of the plant

Other Variables:

  • Volume of mineral sloution 
  • Specied of plant
  • Size of container 
  • Amount of light recived

Equipment:

  • Mexican heat plate
  • 7 test tubes
  • Test tube holder
  • Diffrent mieral solutions- each lacking 1 nutient and 1 containing all nutrence
  • Aluminium foil
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Investigating plant mineral deficiencies

Method:

Half fill tube with "all nutrence presant" solution. Cover top of tube with tin foil and push down so that there is a well in the center. Gently push geranium stem/root of mexican hat planled through the hole so that it is in the solution below. Repeat with solution lacking in nitrogen or photphate or potassium of magnesium or calcium or lacking in all (distiled water). Oberver regulaly.

Out come:

The "all nutrience presant" plant will look healthy, where asthe others will all have some abnormality. Make sure you know what nutrient difficencys affect plants.

Evaluation issues:

  • Ensure accurate mesurements of solutions
  • No air bubles caught in xylem of geranium 
  • Possible microorganism growth in nutient solution
  • insuffucient time to see effect 
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Effect of garlic and mint on bacterial growth

Independent variable: presence of garlic or mint

Dependent varible: Zone of inhabition around disc

Other Variables:

  • Concentration of plant material
  • Lawn of bacteria on petri dish
  • contamination os petris dish by other microbes
  • same volume of plant material on each disc

Equipment:

  • Agar plate seeded with bacteria Sterile petri dish
  • Plant material eg garlic and mint Sterile forseps
  • Pestal and mortar Hazard tape 
  • 10cm^3 industrial denatired alcohol Marker pen
  • sterile pipette 
  • paper discs
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Effect of garlic and mint on bacterial growth

Method:

Make a plant extract by crushing 3g of plant material with 10cm^3 industral senatured alcohol. shake occasionally for 10 minits. Pipette 0.1cm^3 of extract onto sterile paper sidc. alow to dry on terile petri dish. Meanwhile labe agar plates with date and split in to 4 sections. One for each type of plant exstract. Place 1 disc of each exstract in each quadrant of the agar plate, close and tape with hazard tape. leave to incubate over night and observe zone of inhibition. Carrie out controls with just distilled water on disc.

Out come:

the control disc compleatly coverd with bactira, some plant exstract will create larger zones of inhibition than others, meaning they are more effective at lower concentrations.

Evaluation issues:

  • Growth of unwanted microbes ob agar plates due to bad aseptic tevhniques
  • not shaking exstract enouth to ensure enough active ingredent
  • Inconsistency when adding plant extract to paper discs.
  • Contmaminationg controls
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Comments

Mubarak Mohamoud

very useful , cheers !

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