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Syllabus

9.3 Growth in plants

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Additional higher level » Topic 9: Plant biology » 9.3 Growth in plants

Description

Nature of science:
Developments in scientific research follow improvements in analysis and deduction—improvements in analytical techniques allowing the detection of trace amounts of substances has led to advances in the understanding of plant hormones and their effect on gene expression. (1.8)

Understandings:

Undifferentiated cells in the meristems of plants allow indeterminate growth.
Mitosis and cell division in the shoot apex provide cells needed for extension of the stem and development of leaves.
Plant hormones control growth in the shoot apex.
Plant shoots respond to the environment by tropisms.
Auxin efflux pumps can set up concentration gradients of auxin in plant tissue.
Auxin influences cell growth rates by changing the pattern of gene expression.

Applications and skills:

Application: Micropropagation of plants using tissue from the shoot apex, nutrient agar gels and growth hormones.
Application: Use of micropropagation for rapid bulking up of new varieties, production of virus-free strains of existing varieties and propagation of orchids and other rare species.

Guidance:

Auxin is the only named hormone that is expected.

Theory of knowledge:

Plants communicate chemically both internally and externally. To what extent can plants be said to have language?

Utilization:

Micropropagation is used for rapid bulking up of new varieties of plant.

Syllabus and cross-curricular links:
Biology
Topic 3.5 Genetic modification and biotechnology

Aims:

Aim 6: Investigations into tropisms could be carried out.

Directly related questions

16N.1.HL.TZ0.34:
What is/are the effect(s) of auxin in plants?

I. Increasing the rate of cell elongation in stems
II. Changing the pattern of gene expression in shoot cells
III. Detecting the direction of light

A. I only
B. I and II only
C. II and III only
D. I, II and III
17M.1.SL.TZ1.1: Which structure found in eukaryotes has a single membrane? A. Nucleus B. Lysosome C....
17M.2.HL.TZ2.1e: Based on all the data presented and your knowledge of auxin, discuss the pattern of auxin...
17M.2.HL.TZ2.1d.i: Compare and contrast the changes in auxin concentration in the stem base over time for the...
17M.2.HL.TZ2.1f.ii:
Compare the pattern of GH3 transcription with the pattern of auxin concentration in the stem base control cuttings. You may use the table provided to help you to record the patterns before you compare them. (Please note: a simple
comparison in the table will not gain marks)
17M.2.HL.TZ2.1f.iii: The scientists concluded that auxin activates the transcription of the GH3 gene. Using the...
17M.2.HL.TZ2.1a: Calculate the difference in the concentration of auxin found in L1 and L6. . . . . . . . . . . ....
17M.2.HL.TZ2.1b: Identify the relationship between the concentration of auxin and the age of the different leaves.
17M.2.HL.TZ2.1c: Analyse the effect of NPA on the formation of roots.
17M.2.HL.TZ2.1d.ii: Deduce the effect of NPA on auxin transport between L6 and the stem base.
17M.3.HL.TZ2.1a: In order to form galls, the insects choose a location where cell division occurs at a high rate....
20N.1.HL.TZ0.33: How does auxin exert its effect on plant cells? A. Acts directly on the cell wall, causing...
21M.1.HL.TZ1.40: Expansin is a plant protein that loosens connections between cellulose fibres in plant cell...
21M.1.HL.TZ2.34: How does auxin contribute to phototropism? A. It increases production of light-sensitive...
21M.2.HL.TZ1.6b:
Outline how the hormone auxin controls phototropism in plant shoots.
21M.2.HL.TZ2.3a:
On the diagram, label the testa and the radicle.
21N.1.HL.TZ1.33:
The diagram shows a plant shoot and the direction of the light which the shoot received.

[Source: USDA-NRCS PLANTS Database. Available at: https://commons.wikimedia.org/wiki/File:Alnus_seedling_drawing.png
[Accessed 30 November 2021].]

What are the direction of movement and the effect of auxin in the tip of a plant shoot when receiving light from one side?
21N.2.HL.TZ0.5c:
Outline the extension of the stem in plants.
22M.1.HL.TZ2.33:
The picture shows lentils sprouts growing towards a light source from the left.

[Source: Russell Neches, Lentil sprouts reaching for the sun [image online] Available at https://www.flickr.com/photos/rneches/2081938105/ This file is licensed under
the Creative Commons Attribution 2.0 Generic (CC BY 2.0)
https://creativecommons.org/licenses/by/2.0/.]

How has this response been brought about?

A. A higher concentration of auxins on the light side caused faster photosynthesis.

B. A higher concentration of auxins on the shaded side caused faster meiosis.

C. A higher concentration of auxins on the shaded side caused faster cell elongation.

D. A higher concentration of chloroplasts on the light side allowed for more photosynthesis.
22M.1.HL.TZ1.34: What is an aspect of indeterminate growth in plants? A. The shoot apex retains undifferentiated...
18N.2.SL.TZ0.3b: In some areas there are gaps in the boreal forest where trees fail to grow and peat tends to...
18N.2.HL.TZ0.4b: In some areas there are gaps in the boreal forest where trees fail to grow and peat tends to...
18N.2.HL.TZ0.8b: Describe the roles of the shoot apex in the growth of plants.
18M.1.HL.TZ2.30:
The image shows seedlings that have been exposed to unidirectional light.

[Source: The Micro Gardener (https://themicrogardener.com/prevent-fix-leggy-seedlings/)]

Which statement explains the growth towards the light source?

A. Light causes auxin to inhibit cell division in the shoot meristem.

B. Light causes auxin to promote cell division in the shoot meristem.

C. Auxin is concentrated in the side of the shoot with light and inhibits cell elongation.

D. Auxin is concentrated in the side of the shoot without light and promotes cell elongation.
19M.1.HL.TZ2.39:
The photomicrograph shows a section through the top of a plant shoot.

[Source: Charles Good: The Ohio State University at Lima]

What are the structures labelled X and Y?
19N.2.HL.TZ0.8b: Outline the growth of plant shoot apex.

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DP Biology Questionbank

9.3 Growth in plants

Description

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