Page 25 - Biology_Form_3

Biology for Secondary Schools

(d) The plant is exhibiting (b) The plants show hydrotropism,
thigmotropism, with cytokinins with gibberellins controlling
promoting the opening of flowers growth toward water.
in high light intensity and closing
in dim light. (c) The plants are exhibiting
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gravitropism, with auxins and
10.You are experimenting with two ethylene influencing growth in
potted plants. One plant is placed response to gravity.
side wise for a few days, while the
other remained upright. In both (d) The plants are responding
plants, roots grows downward and to mechanical stimuli, with
shoots upward. Which plant hormone cytokinins promoting growth in
and phenomenon best explains the response to touch.
directional growth of both plants?
11. Match the hormones in Column A
(a) The plants exhibit phototropism, with the corresponding function in
with auxins causing growth Column B by writing the letter of the
toward light. correct function next to the question
in Column A.

Column A Column B
(i) Cytokinin A. Influence water retention
B. Influence formation of branches and leaves
(ii) Gibberellins
C. Make plants repel light rays
(iii) Auxin D. Promote cell elongation in stems and roots

(iv) Abscisic Acid E. Regulate fruit size
F. Promote water loss from leaves
(v) Ethylene G. Influence fruit type
H. Helpful in stress management
I. Maintain uprightness of plants
J. Its production decreases with shoot exposure to light
Answer the following questions 14. Imagine you are a gardener

12. Describe the characteristics of auxins tasked with optimising the growth
that lead to the success of phototropic conditions for a variety of climbing
and geotropic movements in plants. plants which exhibit thigmonastic
movements. Explain the advantages
13. What is the role of hydrotropic
movement in the growth and of this plant movement in the plant’s
productivity of the plant? survival and propagation.

18 Student’s Book - Form Three

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