Biology · Edexcel Paper 2
Plant Adaptations and Hormones
How plants are adapted to survive in extreme environments through their leaf size and shape, their cuticle and their stomata, how plant hormones called auxins control growth towards light and gravity, how to investigate tropic responses, and how auxins, gibberellins and ethene are used commercially. Matches Edexcel 6.14B to 6.16B, which are marked B in the specification. This chapter is for separate Biology only: Combined Science students do not need it. Plant hormones and tropisms, and investigating tropic responses, are for both tiers. The commercial uses of plant hormones (6.16B) are for the Higher tier only.
Lessons
Ticks are remembered on this device only.
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1
Plants in Extreme Environments
A cactus in the desert, marram grass on a windy dune and a water lily on a pond all face very different problems. This lesson is for separate Biology only…
9 terms -
2
Plant Hormones and Tropisms
A plant has no nerves or muscles, but it still grows towards the light and sends its roots down. This lesson is for separate Biology only: Combined Science…
9 terms -
3
Investigating Tropic Responses
You can see a tropism happening in a few days with a pot of cress seedlings. This lesson is for separate Biology only: Combined Science students do not need…
9 terms -
4
Commercial Uses of Plant Hormones (Higher tier)
Farmers and growers use plant hormones to control how their crops grow and ripen. This lesson is for separate Biology only, and for the Higher tier only…
9 terms
Key terms in this chapter
All 36, gathered from every lesson.
- Adaptation
- A feature of structure or behaviour that helps an organism to survive in its environment.
- Xerophyte
- A plant that is adapted to live in a very dry habitat.
- Cuticle
- A waxy waterproof layer on the surface of a leaf or stem.
- Stoma
- A pore in the surface of a leaf, surrounded by two guard cells, which lets gases pass.
- Transpiration
- The loss of water vapour from a plant, mainly from the leaves.
- Surface area to volume ratio
- The surface area of an object divided by its volume.
- Humid
- Containing a lot of water vapour.
- Extreme environment
- A habitat where conditions such as temperature or water are very hard to survive.
- Spine
- A leaf that has become a sharp, narrow structure, as in a cactus.
- Plant hormone
- A chemical made in a plant which controls and coordinates growth and development.
- Auxin
- A plant hormone, made in the tip of the shoot and the root, which controls cell elongation.
- Tropism
- A growth response of a plant to a stimulus from one direction.
- Phototropism
- Growth in response to the direction of light.
- Gravitropism
- Growth in response to gravity.
- Elongation
- The growth of a cell by getting longer.
- Stimulus
- A change in the environment that a plant or animal detects.
- Positive tropism
- Growth towards the stimulus.
- Negative tropism
- Growth away from the stimulus.
- Clinostat
- A device that turns plants slowly so that gravity acts on all sides equally.
- Seedling
- A very young plant that has just grown from a seed.
- Control
- A test in which the factor being investigated is not changed, for comparison.
- Independent variable
- The variable that you change.
- Dependent variable
- The variable that you measure.
- Control variable
- A variable that you keep the same.
- Anomaly
- A result that does not fit the pattern.
- Mean
- The sum of the values divided by the number of values.
- Protractor
- An instrument for measuring angles.
- Weedkiller
- A chemical that kills weeds, which are unwanted plants.
- Selective weedkiller
- A weedkiller that kills some kinds of plant but not others.
- Rooting powder
- A powder that contains auxin, used to make cuttings grow roots.
- Gibberellin
- A plant hormone that ends seed dormancy and promotes flowering and the growth of fruit.
- Ethene
- A gas that is made by plants, and makes fruit ripen.
- Seedless fruit
- Fruit that grows without any seeds.
- Cutting
- A piece of a plant which is used to grow a new plant.
- Dormancy
- A resting state of a seed, in which it does not germinate.
- Synthetic
- Made by people, and not found in nature.