(a)(i) Define tropic and nastic movements.
(ii) List four differences between tropic and nastic movements.
(b) Describe an experiment to show that auxins are produced in the apical cells of a shoot.
(c)(i) Name two plant hormones, other than auxins.
(ii) Give two examples of tropism.
(ii) List four differences between tropic and nastic movements.
(b) Describe an experiment to show that auxins are produced in the apical cells of a shoot.
(c)(i) Name two plant hormones, other than auxins.
(ii) Give two examples of tropism.
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Correct Answer: Option n
Explanation:
(a) Definition of tropic and nastic movements:
(i) Tropic movement is growth movement of plant organs in response to external unilateral or directional stimulus. Nastic movement is the movement of certain parts of plants in response to diffuse or non-directional stimulus.
(ii)
Experiment to show that auxins are produced in the apical cells of a shoot:
Aim: To show that auxins are produced in the apical cells of a shoot.
Material: 3 potted seedlings of maize labelled A, B and C; agar block, sharp knife/cutting instruments, mica sheet / aluminium foil/cover slip.
Methods:
(i) Cut tip of coleoptile/shoot in Ato serve as control
(ii) Leave decapitated shoot for about 48 hours
(iii) Select another potted seedling, B,.and cut off tip of coleoptile/shoot
(iv) Place the cut tip on an agar block for about 2 — 6 hours
(v) Place agar block on stump of the decapitated shoot and leave for about 48 hours
(vi) Select a third seedling, C, and cut off tip of the coleoptile
(vii) Place tip of the cut coleoptile on mica sheet for 2 — 6 hours
(viii)Place mica sheet on cut surface of decapitated shoot and leave for about 48 hours.
Observation: Growth ceased in decapitated shoot A, but when agar block was placed on stump of shoot B in which growth had stopped, growth resumed. When mica sheet was placed on stump of shoot C in which growth had stopped, growth did not take place (resume).
Conclusion: This shows that a chemical substance (auxin) produced at the tip, i.e., apical cell of the shoot is responsible for the growth of the shoot.
(c)(i) Names of plant hormones other than auxins are
Gibberellic acid / Gibberellin
2, 4 - D 2, 4 - Dichlorophenozy acid
cytokinis/kinins/kinetin
abscisic acid/abscisin
ethylene/ethene
traumatin
florigen
dormin
formin, etc.
(ii) Examples of tropisms are:
geotropism
hydrotropism
thigmotropism/Haptrodropism
photoropism
stereotropism
chemotropism
thermotropism.
(a) Definition of tropic and nastic movements:
(i) Tropic movement is growth movement of plant organs in response to external unilateral or directional stimulus. Nastic movement is the movement of certain parts of plants in response to diffuse or non-directional stimulus.
(ii)
| Tropic movement | Nastic movement |
| Movement is not easily reversible.Response leads to growth.Movements are not due to change in cell turgor.Response is towards the direction of the stimulus.Response is slow.Responses are not due to pressure. | Movement is reversible.Response does not lead to growth.Movements are due to changes in cell turgor.Response is not Directed to the stimulus.Response is rapid.Responses are due to pressure. |
Experiment to show that auxins are produced in the apical cells of a shoot:
Aim: To show that auxins are produced in the apical cells of a shoot.
Material: 3 potted seedlings of maize labelled A, B and C; agar block, sharp knife/cutting instruments, mica sheet / aluminium foil/cover slip.
Methods:
(i) Cut tip of coleoptile/shoot in Ato serve as control
(ii) Leave decapitated shoot for about 48 hours
(iii) Select another potted seedling, B,.and cut off tip of coleoptile/shoot
(iv) Place the cut tip on an agar block for about 2 — 6 hours
(v) Place agar block on stump of the decapitated shoot and leave for about 48 hours
(vi) Select a third seedling, C, and cut off tip of the coleoptile
(vii) Place tip of the cut coleoptile on mica sheet for 2 — 6 hours
(viii)Place mica sheet on cut surface of decapitated shoot and leave for about 48 hours.
Observation: Growth ceased in decapitated shoot A, but when agar block was placed on stump of shoot B in which growth had stopped, growth resumed. When mica sheet was placed on stump of shoot C in which growth had stopped, growth did not take place (resume).
Conclusion: This shows that a chemical substance (auxin) produced at the tip, i.e., apical cell of the shoot is responsible for the growth of the shoot.
(c)(i) Names of plant hormones other than auxins are
Gibberellic acid / Gibberellin
2, 4 - D 2, 4 - Dichlorophenozy acid
cytokinis/kinins/kinetin
abscisic acid/abscisin
ethylene/ethene
traumatin
florigen
dormin
formin, etc.
(ii) Examples of tropisms are:
geotropism
hydrotropism
thigmotropism/Haptrodropism
photoropism
stereotropism
chemotropism
thermotropism.