(a)(i) Name two types of germination of seeds giving one example of each type. (ii) Describe a simple experiment to demonstrate that oxygen, water and warmt...

Answer Details

(a)(i) Two types of germination of seeds, with examples

• Epigeal germination - the cotyledons are carried above the soil surface. Example: cowpea (or groundnut).
• Hypogeal germination - the cotyledons remain below the soil surface. Example: maize (or oil palm).

(a)(ii) Experiment to show that oxygen, water and warmth are necessary for germination

Aim: To demonstrate that seeds need oxygen, water and warmth to germinate.

Set up four boiling tubes (labelled A, B, C, D), each containing a few viable bean seeds resting on cotton wool:

The boiled, cooled water in C removes dissolved oxygen and the oil layer prevents air from re-entering. Leave the tubes for several days (about a week).

Observation: Only the seeds in tube A (the control), which has water, air/oxygen and warmth, germinate. The seeds in B (no water), C (no oxygen) and D (no warmth) fail to germinate.

Conclusion: Since germination occurs only when water, oxygen and warmth are all present, these three factors are necessary for the germination of seeds.

(b) Distinguishing features

(i) Two features of epiphytes

• They grow on (are attached to) other plants for support but are not parasitic.
• They possess special aerial (clinging) roots and manufacture their own food, absorbing moisture from the air/rain.

(ii) Two features of parasites

• They live on or in a host from which they obtain their food (they possess haustoria that penetrate the host tissues).
• They usually lack chlorophyll or have it reduced, and they harm the host.

(c) Two examples of parasitic plants

Cassytha (dodder / love-vine) and mistletoe (Loranthus / Tapinanthus); Striga is another.