Equipment
Method
- cereal grains
- gibberellic acid 1 gdm'3 stock solution
- 3% sodium hypochlorite bleach
- distilled water
- muslin
- Petri dishes with starch agar
- small beaker
- adhesive tape
- scalpel
- iodine in potassium iodide solution
- forceps
- volumetric glassware and measuring cylinders as required for dilutions of gibberellin
- small sterile containers for soaking grains
- tile
- marker pen
Method
- Day 1
- Make up your gibberellin solutions as planned. Only small volumes (a few cm^3) of each are required. Place each solution in a small labelled sample bottle. Collect the number of seeds that you require and pull any husks off the grains so the shape can be seen clearly. Cut each seed across the line X-Y (see fig A) so that one half contains the embryo and the other the endosperm. Keep the two halves separate and discard the seed halves that contain the embryo. Sterilise the remaining endosperm halves of the seeds by placing them in 3% sodium hypochlorite solution for 5 minutes. Wash the seeds thoroughly, but quickly. through have changes of sterile water, draining carefully through muslin each time, until there is no smell of chlorine. Drain fully. Using sterile forceps, place the seed halves into the gibberellin solutions. Leave for 12-48 hours with the screw tops slightly loose to allow oxygen to enter.
- Day 2; Collect one sterile Petri dish containing starch agar for each of your planned concentrations and label them on the underside. Using sterile forceps, place a number of seed halves onto the agar with the cut face down.Tape each lid with two pieces of tape and incubate for 24-48 hours
- Day 3; Remove the plates from the incubator. Opening the lids slightly, pour a solution of iodine in potassium iodide all over the surface of the agar in each dish. Once stained, pour off into a waste container. Measure the clear zone as planned and record your observations in a suitable table.