Page 22 - Biology_Form_3

Coordination in plants

Part A Part B
(i) This type of plant movement is caused A. Phototropism
by external stimuli and results in growth B. Geotropism
towards or away from the stimulus.
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C. Thermotropism
(ii) An example of a tropic movement when
roots grow downward and shoot upward. D. Thigmotropism

(iii) Is typically rapid and do not involve growth. E. Chemotropism

(iv) A water loving growth response. F. Hydrotropism
G. Nastic movement
(v) A contact growth response in plants. H. Tropic movement
I. Chemonasty

2. Explain at least two benefits of each of the following tropisms in plants:

(a) Geotropisms
(b) Chemotropisms
(c) Hydrotropisms

Chapter summary low concentration promotes growth of

1. Plants detect changes in the roots.
environment. They respond to 4. Gibberellins promote plant growth by
environmental changes by using stimulating cell elongation leading to
hormones.
increased stem growth. It also promotes
2. Plant hormones or plant growth seed germination by breaking seed
hormones are chemical substances dormancy.
that regulate plant growth. They are
also known as phytohormones or plant 5. Abscisic acid (ABA) is a plant
growth regulators. hormone involved in various
physiological processes. During
Examples of plant hormones include drought conditions, ABA is produced
Auxins, abscisic acid, gibberellins and in the roots and transported to the
cytokinin. leaves, where it triggers the stomata
closure, thereby reducing water loss
3. Auxin is a plant hormone that plays through transpiration. Generally, ABA
a key role in regulating growth and is essential for plant survival under
development of the plant. Normally, harsh environmental conditions and
the higher concentration of auxins in regulating plant developmental
promotes the growth of shoots while processes such as growth and dormancy.

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