Chapter 9 - Plants as organisms

Question 1

Photosynthesis summary

Answer 1

C02 taken in by leaves and water taken up by roots, chlorophyll traps light energy needed and this energy is used to convert the C02 and water into glucose. Oxygen is released as a by product and some glucose is converted into insoluble starch for storage.

Question 2

Iodine test on leaves

Answer 2

Starch is identified by the solution turning blue/black in the green patches.

Question 3

Limiting factors

Answer 3

Anything that stops the rate of photosynthesis above a certain level: lack of light (energy), cold (ineffective enzymes) and lack of carbon dioxide.

Question 4

Greenhouses and polytunnels

Answer 4

Optimum temperature for enzyme activity, C02 levels increased, artificial lighting extends amount of time plants photosynthesise. Costly but higher yield = more profit

Question 5

Uses of soluble glucose

Answer 5

Converted to insoluble starch for storage in organs, respiration, converted into fats and oils for storage, to produce cellulose (strengthens cell walls) and to produce proteins.

Question 6

Venus flytrap

Answer 6

Carnivorous plant, adapted to live in nutrient-poor soil, obtains most of its nutrients from the animals it digests. Obtains nitrates by digesting animal protein.

Question 7

Plants respire

Answer 7

24 hours a day

Question 8

Glucose is soluble in

Answer 8

Water but starch is insoluble. I

Question 9

Stomata

Answer 9

Small holes in leaves that gases (oxygen for respiration and carbon dioxide for photosynthesis) diffuse in and out of. Size of the stomata is controlled by the guard cells around them. Close to prevent wilting.

Question 10

Waxy cuticle

Answer 10

Waterproof layer that prevents water loss

Question 11

Leaves

Answer 11

Flat and thin so gases of t have to diffuse far

Question 12

Root hair cells

Answer 12

Increases surface area of roots for absorption of water and mineral ions.

Question 13

Layers of tissues in leaves

Answer 13

Upper epidermis
Palisade layer
Spongy layer
Lower epidermis

Has plenty of air spaces and shot diffusion distances for efficient gas diffusion.

Question 14

Transpiration

Answer 14

Water taken through roots, passed through the plant to leaves, water evaporates and vapour diffuses through stomata.

Question 15

Transpiration stream

Answer 15

The movement of water through a plant

Question 16

Evaporation

Answer 16

More rapid in hot dry or windy conditions, plants dehydrate if the rate of evaporation is greater than the water uptake by the roots.

Question 17

Wilting

Answer 17

Reduces water loss as the leaves collapse and hang down which reduces s.a.

Question 18

Xylem tissue

Answer 18

Transports water and mineral ions from roots to stem.

Question 19

Phloem

Answer 19

Carries dissolved sugars from the leaves to the rest of the plant including growing regions and storage organs = translocation.

Question 20

Phototropism

Answer 20

Plant shoot grow towards the light

Question 21

Gravitropism

Answer 21

Roots grow down toward gravity.

Question 22

Hydrotropism

Answer 22

Roots grow towards water.

Question 23

Auxin

Answer 23

Hormone controlling phototropism and gravitropism.

Question 24

Roots

Answer 24

More auxins gather on lower side. Grows more on the side with least auxins so bends and grows towards force of gravity, once it has grown down auxins become once again evenly spread.

Question 25

Shoots

Answer 25

More auxins gather on the lower side, the shoot grows more on the side with the most auxins making it bend and grow up, until the auxins become evenly spread again.

Question 26

Plant hormones

Answer 26

Used as weed killer and to stimulate root growth.

Question 27

Cuttings

Answer 27

When cuttings are taken from plants,hormones are used to encourage roots to grow before the cutting is planted.

Question 28

Problem with plant hormones

Answer 28

If used incorrectly can cause damage to environment such as harming other plants.

Question 29

Pollination

Answer 29

Anther produces male gametes in pollen grains. Anther is attached to filament to form stamen. Pollen grains carried by wind etc to carpel (female part). Carpel is made of stigma, style and ovary. Pollen grains attach to stigma and pollination occurs when pollen is attached to stigma.

Question 30

Wind pollinated flowers

Answer 30

Small, light pollen grains, anthers outside of flower, small petals and large stigmas outside petals.

Question 31

Insect pollinated flowers

Answer 31

Large brightly coloured petals, scent, nectar, large sticky pollen grains to attach to insects and anther and stigma inside flower so insects brush against them when collecting nectar.

Question 32

Equation

Answer 32

Carbon dioxide + water = glucose + oxygen

Question 33

Fertilisation

Answer 33

Pollen grains attach to stigma on top of carpel , where ovules are and pollen tube grows through style into ovule. Two male nuclei from pollen grain migrate into ovule to fertilise egg nucleus and endosperm nuclei. Zygote develops into embryo and endosperm forms food store. Endosperm and female tissues give rise to seed, ovary grows into fruit which surrounds the seed.