Theory question 102
Growth and Development(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 warmth are necessary for germination of seeds.
(b) State two distinguishing features each of (i) epiphytes; (ii) parasites.
(c) Give two examples of parasitic plants.
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(a)(i) Epigeal, e.g. bean/cowpea; hypogeal, e.g. maize/pea.
(ii) Set up four flasks with moist cotton wool and seeds: A — dry cotton wool (no water), warm; B — water, but alkaline pyrogallol in the flask to absorb oxygen, warm; C — water and air, kept in a refrigerator (cold); D — water, air and warmth (control). After 3–5 days only seeds in D germinate, showing that water, oxygen and warmth are all needed.
(b)(i) Epiphytes: grow on other plants only for support/light; make their own food (have chlorophyll); do not harm the host; often have aerial roots that absorb moisture from the air.
(ii) Parasites: obtain food from a living host; harm the host; often lack chlorophyll; have haustoria that penetrate the host's tissues.
(c) Any two: dodder (Cuscuta), mistletoe (Loranthus), Striga (witchweed).
In the experiment each flask lacks one condition and a control has all three.