Water transport and salinity

Lab 6A: Water transport and salinity

1. Examine the top of the celery stalks. Are there differences between the celery in the high salt and low salt water conditions? Describe your observations.

2. Record the distance (cm) traveled by the red dye in high salt conditions (S), the blue dye in high salt conditions (S), the red dye in low salt conditions (non-S) and the blue dye in low salt conditions (non-S).

Table 6.1

Distance (cm)

Red dye (S)

Blue dye (S)

Red dye (non-S)

Blue dye (non-S)

3. From Question 2 above, did the dyes travel at the same rate? What can you conclude about the effect of salinity on water transport in celery from this experiment? Propose a biological or physical explanation for your conclusion.

Activity: seeds

1. Obtain a sugar snap pea pod, or a snow pea pod. This is the fruit that develops from the pea flower (Figure 5.4). In this case, the fruit is not as sweet or as juicy as an apple. Cut along the curve of the pod. This exposes the seeds (peas) on the inside. You should be able to crack the peas in half. This reveals that the seed is composed of two cotyledons (seed “leaves”). The cotyledon becomes the main food source as the seed starts sprouting.

2. Angiosperm plants are divided into dicots (Class Dicotyledonae) and monocots (ClassMonocotyledonae). There are 180,000 species of dicots, including many flowers, shrubs,and trees. Dicots are distinguished by seeds with two cotyledons (e.g., bean, peanut, pea),leaves with veins having a branching pattern (e.g., maple, oak), and flower parts in multiples of four or five (e.g., four petals of poppies, five petals of wild roses). There are 80,000 species of monocots, including grasses and important crops (e.g., wheat, corn, rice), palms, and orchids. Monocot seeds have one cotyledon (e.g., corn kernel), leaves with parallel veins (e.g., blade of grass), and flower parts in multiples of three (e.g., six petals on lilies).

3. Obtain a few dry lima beans. Soak them in a cup of tap water for at least 8 hours.

4. Gently dry the beans on a paper towel. With your finger, you should be able to gently peel off the outer seed coat (if you cannot, soak the bean for 1-2 more hours).

5. Using a knife, carefully cut along the curvature of the bean. You should then be able to break the bean in half. Each half is a cotyledon, which has become swollen with nutrients from the endosperm.

6. Examine the embryo (see Figure 5.3). At minimum, you should be able to recognize the leaflike tip of the epicotyl (Figure 5.4). Look for the hypocotyl and the radicle.

5.3

5.4 5.4

5.4