IB Biology 2015 Curriculum Plant Science student notes

1. Understandings, Applications and Skills (This is what you may be assessed on)
Statement Guidance
9.3 U.1 Undifferentiated cells in the meristems of plants allow indeterminate growth.
9.3 U.2 Mitosis and cell division in the shoot apex provide cells needed for extension
of the stem and development of leaves.
9.3 U.3 Plant hormones control growth in the shoot apex
9.3 U.4 Plant shoots respond to the environment by tropisms.
9.3 U.5 Auxin efflux pumps can set up concentration gradients of auxin in plant tissue.
jk9.3 U.6 Auxin influences cell growth rates by changing the pattern of gene expression.
9.3 A.1 Micropropagation of plants using tissue from the shoot apex, nutrient agar gels
and growth hormones.
9.3 A.2 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.
1. Draw and label diagram of a dicot plant below. (Slides 57-58)
2. Draw and label diagram of a cross section of dicot stem below. (Slides 59-60)

2. 9.3 U.1 Undifferentiated cells in the meristems ofplants allowindeterminate growth.
3. Define meristem. (Slide 61)
4. Distinguish between apical and lateral meristems in terms of location and function in the stem.
(Slide 62)
5. Describe the function of the axillary bud. (Slide 65)
6. Explain where lateral meristematic growth takes place? (Slide 66)
9.3 U.2 Mitosis and cell division in the shoot apex provide cells needed for extension ofthe stem and
development ofleaves.
7. Explain why meristem cells are more likely to be in mitosis than cells found in other parts of the
plant. (Slide 67)
9.3 U.3 Plant hormones control growth in the shoot apex
8. What is a plant hormone? (Slide 68)
9. Fill in the chart below. (Slide 68)
Hormone Name Hormone Response
10. What types of physiological responses are caused by Auxin and cytokines together? (Slide 69)

3. 11. Explain how the plant hormone Auxin effects grow in a plant cell. (Slides 71-75)
9.3 U4 Plant shoots respond to the environment by tropisms.
12. Define tropism. (Slide 76)
13. Define auxin.
14. Explain, with the aid of a diagram, the role of auxins in phototropism. (Slide 77)
9.3 U.5 Auxin efflux pumps can set up concentration gradients ofauxin in plant tissue.
15. In roots, does auxin have the same or the opposite effect as auxin in shoots? (Slide
80)
16. Why has the root bent downwards in area X?
17. Why has the shoot bent upwards in area Y?
18. Plant roots are also attracted towards moisture. Explain whether auxin moves towards
or away from moisture. Drawing a diagram may help you.
9.3 A.1 Micro propagation ofplants using tissue from the shoot apex, nutrient agar gels and growth
hormones.
In 1880, Charles Darwin did some experiments on the growth of plant shoots. These are shown
in the drawings below: (Slides 81-83)
15. Describe what happened in each of these experiments.

4. We now know that plant hormones cause these things to happen. In experiment A, the light causes a plant
hormone called auxin to move towards the darker part of the shoot.
16. Draw the pictures for experiment A, showing what happens to the auxin.
17. What effect does auxin have on the part of the shoot it moves to?
18. Why is this useful to the plant?
19. Do you think auxin is found in all parts of a shoot, or only at the tip? Use the drawings
above to help with your explanation.
20. The drawing below shows a root that has bent downwards and a shoot that has bent
upwards
9.3 U.6 Auxin influences cell growth rates by changing the pattern ofgene expression. (Slides 61-66)
21. Explain one way in which Auxin effects a change in growth in the plant.
22. What would happen to a plant that is unable to make Auxin or contain reduced amounts of
Auxin?
9.3 A.2Use ofmicropropagation for rapid bulking up of newvarieties, production ofvirus-free
strains ofexisting varieties and propagation oforchids and other rare species.
23. Explain the benefits to using micro propagation. (Slide 86)