?Experiment 5. Uptake of water by an uprooted plant – preparation Outline A small uprooted plant is sealed into a 5 or 10 cm3 plastic syringe barrel with ‘Blu-tack’ or similar material and fitted to a potometer. Prior knowledge The questions assume that the student has an understanding of photosynthesis. Advance preparation and materials Plants. Dig up small plants (e. g. garden weeds) 10-20 cm tall and wash as much soil as possible off their roots.
Select those whose root system can be fitted into a 5 or 10 cm3 syringe barrel; remove leaves as necessary from the bottom 2 cm of the stem and keep the plants in the shade in a jar of water until needed. Syringe barrel. The narrow pattern of a 10 cm3 syringe is particularly suitable. Small plants will fit comfortably into a 5 cm3 syringe barrel. Provide a selection appropriate to the sizes of plants collected. Plastic sealing material.
‘Blu-tack’ and similar materials (from stationers) form a good seal and are easy to remove from the plant and the syringe. ‘Plasticine’ is effective but is more difficult to remove. Provide a ball of about 2 cm diameter (about 6 grams) for each experiment. Potometer. This is described on p. 2. 04. The upper piece of pressure tubing is removed for this experiment. Needles.
The needles on the syringe used to fill the barrel should be as wide as possible to pass through the Luer fitting (e.g. Size No. 1, green hub) and it is advisable to cut the points off and rub the ends down on a grindstone to avoid accidents. Insert a wire through the needle during this operation to avoid it becoming clogged with abrasive. Paper towels to dry the stems. Apparatus-per group potometer and syringe barrel as described above 1 cm3 syringe for potometer 5 or 10 cm3 syringe and blunt needle small jar for water retort stand and clamp stop-clock or sight of clock with second hand.