First Laboratory Exercise

Today we will do some simple chores to set up future laboratory exercises. We will sow some spores on Knopp's medium, which contains the minerals plants need to obtain from the soil around their roots. Growing plants without soil is called hydroponics. In this case we are solidifying the liquid with a very small amount of Phytagel (a substance similar to agar). The mineral macroelements include P, K, N, S, Ca, Fe, and Mg while the microelements include B, Mn, Zn, Cu, and Mo. Phytagel is used at 0.8 grams per 250 mL. We will also learn to use a dissection microscope properly to be sure the spores we have sown have indeed entered the container of gel. We will also prepare soil and pots for germinating seeds. You will work with one partner as a team of two.

  1. Approximately 25 mL of autoclaved Knopp's phytagel medium were allowed to solidify on cooling in 10 cm Petri dishes. You will distribute, as sparingly as possible, the spores of Polytrichum moss in one dish and the spores of Ceratopteris fern in another dish. Use the dissection and/or light microscope to determine that spores indeed are present on the surface of the gel. Place the dishes into the tray for incubation under illumination by fluorescent light. Can you guess why placing these dishes in the greenhouse would be inappropriate?
  2. Prepare a batch of friable potting soil. Fafard #2 is the mix of peat, perlite, and vermiculite that we use. Add water and mix with your hands until the soil is moist enough to form a ball on your hand when you squeeze it together, but is dry enough for the ball of soil to crumble on a touch. This condition is called friable.
  3. Pack the friable soil into 4.5" Geranium pots (sorry, but the industry uses English measurements, but = 11cm) so that the surface is level and firm and up to the level of the ridge inside the rim of the pot (i. e. down about 3 cm from the rim).

    In one pot, place eight popcorn (Zea mays) seeds in a circular pattern about a centimeter from the edge of the soil. In a second pot, place six Roman Bean (Phaseolus vulgaris) seeds in a similar pattern.

    Prepare a pot-label for each pot with your name, the date, and the kind of seeds sown written in PENCIL. Insert the label into the soil to its full depth at one edge of the pot, with the writing facing the center of the pot.

    Cover the seeds with friable soil and firm it to be level and at about 1 centimeter below the rim.

    Place the pots in the designated area of the greenhouse.

  4. Repeat the seed planting with the seeds of Brassica rapa 'Petite' but use just four seeds per pot for two pots.
  5. Repeat the seed planting with the seeds of Lactuca sativa 'Tango' but use 10 seeds per pot for two pots. For one of these pots, cover the seeds as you did before, burying them with about 2 cm of friable soil. For the other pot, DO NOT cover the tiny seeds with any soil. Simply press the seeds into firm contact with the moist soil (be sure they don't come out on your finger!). Be sure to include the difference between these two pots on their labels!
  6. Repeat the seed planting in step 4 above with ten seeds of Pisum sativum in each of two pots.

Which of our projects today represent experiments?