I would like to investigate the effect of different wavelength of light on germination of Lactuca sativa. Can you give me some tips to help me get started?
You can place the seeds on filter paper in petri dishes. I find it best to place two sheets of paper in each dish and to use the dishes upside down - placing the paper in the lid and then putting the "base" on top. You will need between 5 and 10 cm3 of water to moisten the paper without flooding the seeds.
You can sprinkle the seeds on the paper - about 10 to 20 in each 10cm dish.
You can simply count how many have germinated after 12, 24, 36, 48 hours etc, picking out the ones which have germinated and discarding them.
Once you have some data like this, THEN you can design an experiment in which you measure the length of the plumule (measuring the root/radicle would be easier) on as small a number of seeds as possible. (say 40 in each light treatment).
You could arrange the data to give means and standard deviations for each treatment you carry out and then use a "students t" test to find out whether the differences are significant.
I hope this gets you started.