2KS3 Plants KS3 Sc1 Science Green plants as organisms 3) Pupils should be taught:that plants need carbon dioxide, water and light for photosynthesis, and produce biomass and oxygento summarise photosynthesis in a word equationthat nitrogen and other elements, in addition to carbon, oxygen and hydrogen, are required for plant growththe role of root hairs in absorbing water and minerals from the soilthat plants carry out aerobic respiration.
3KS4 Double award (Sc2)Students should be taughtabout similarities and differences in structure between plant and animal cellsthe reactants in, and products of, photosynthesisthat the rate of photosynthesis may be limited by light intensity, carbon dioxide concentration or temperaturehow the products of photosynthesis are utilised by the plantthe importance to healthy plant growth of the uptake and utilisation of mineral saltthe hormonal control of plant growth and development, including commercial applicationhow plants take up water and transpirethe importance of water in the support of plant tissuesthat substances required for growth and reproduction are transported within plants.
4What is photosynthesis? Plants make their own food by photosynthesis.This process is a chemical reaction that uses light energy.light energyThe word photosynthesis comesfrom the Greek language:“photo” means “light”“synthesis” means “putting together”Photosynthesis just means “putting together with light”.What do green plants “put together” to make their food?
5Photosynthesis: raw materials The raw materials for photosynthesis come from the air and the soil.What are these raw materials called?What else do plants need to turncarbon dioxideand water into food?carbondioxidewater
6Photosynthesis: energy for the reaction Photosynthesis is a chemical reaction between carbon dioxide and water.Energy is needed for this reaction to take place.Where do plants get this energy from?light energycarbondioxidewater
7carbon dioxide water Photosynthesis takes place in plant cells light with chloroplasts.Chloroplasts contain the green chemical called chlorophyll.Chlorophyll absorbs the energy from sunlight that allows carbon dioxide and water to react.What are the products of this reaction?lightenergychlorophyllcarbondioxidewater
8carbon dioxide oxygen oxygen glucose glucose Glucose is the useful product for plants.Some glucose is used straightaway by plant cells, some is converted to starch for storage and later used for food.Oxygen is the ‘waste’ product. This gas is transported out of the leaf into the air.Why is this important for humans and other living things?lightenergychlorophyllcarbondioxideoxygenoxygenglucoseglucosewater
11Photosynthesis: summary Summarize the process of photosynthesis in one sentence.Photosynthesis is a chemical reactionthat takes place in the chloroplastsin green plant cells, where light energyis used to convert carbon dioxide and waterinto glucose and oxygen.Photosynthesis is a chemical reaction which means it can also be summarized in a word equation.What is the word equation for this vital chemical reaction?
12Photosynthesis: word equation light energycarbondioxidewaterglucoseoxygenchlorophylllightenergychlorophyllcarbondioxideoxygenglucosewater
14Photosynthesis: chemical formulae? Photosynthesis is a chemical reaction involving molecules.glucoselight energychlorophyllcarbondioxidewateroxygen666CO2H2OC6H12O6O2The chemical formula of a glucose molecule is C6H12O6.What are the chemical formulae of the simple molecules that make up carbon dioxide, water and oxygen?
15Photosynthesis and respiration Only green plants photosynthesize,but respiration occurs in the cells of all living things to release energy.Photosynthesis(energy needed)glucoselight energychlorophyllcarbondioxidewateroxygenRespiration(energy released)carbondioxideglucoseoxygenwaterCompare the reactants, products and energy results of these two chemical reactions. How are they connected?
16Photosynthesis and respiration How will the amounts of oxygen and carbon dioxide in the air vary over 24 hours?amount ofoxygenamountof gasin the airamount ofcarbon dioxide12 a.m p.m a.m.What overall effect do photosynthesis and respiration have on the levels of oxygen and carbon dioxide in the air?
17How does water enter a plant? Water is one of the raw materials needed for plants to carry out photosynthesis.How does water enter a plant?Water from the soil enters a plant through the roots.You can’t normally see them butroots are a very important part of a plant.Why are roots branched and spread out through the soil?
18How are roots adapted? water Roots are branched and spread out for two reasons:to absorb water (and mineral salts)from a large amount of soil.to anchor the plant in the soil.Taking a closer look, roots arecovered in root hair cells.Root hair cells have thin wallsand a large surface area to helpthem absorb lots of water.How are roots adapted to their job?water
20Why do plants need water? Water is needed by plants for photosynthesis but this important liquid is also used in many other ways:to provide dissolved minerals that keep the plants healthy;to transport substances around the plant;to keep the plant rigid and upright;to keep the plant cool;to allow other chemical reactions to occur in plant cells.What happens to a plant if it does not get enough water?
21Tropisms water hydrotropism light phototropism gravity geotropism Plant responses to light, water and gravity are givenspecial names.waterhydrotropismlightphototropismgravitygeotropismCan you work out what the name of each tropism means?Which parts of a plant respond to these different stimuli?
23Phototropism and auxins – light from one side Why does the shoot bend towards the light when it gets light from one side?There are more auxins on the shaded side of the shoot,so the shaded side grows faster making the bright side bend towards the light.lightlight
24Geotropism and auxinsIf a plant is laid on its side, why does the root grow downand the stem grow up?Auxins slow down growth on the lower side of the root,so the root curves down.Auxins speed up growth on the lower side of the stem,so the stem curves up.
25Plant Responses What do plants respond to? Response to light ContentsPlant ResponsesWhat do plants respond to?Response to lightResponse to gravityResponse to waterUsing plant hormonesSummary quiz
26What are plant hormones used for? Plant hormones can be used in gardening andagriculture to control how plants grow and develop.Plant hormones are naturally-occurring chemicalsbut can also be produced synthetically for the following commercial uses:growing cuttingskilling weedsripening fruit
27Using plant hormones – growing cuttings A cutting is a part of plant thatis removed from the main shoot.What does a cutting no longer have, when it is removed from a plant?A cutting does not have roots andso has no supply of water or minerals.Rooting powder contains plant growth hormones. Dip a cutting into rooting powder and the plant hormones stimulate the cutting to grow new roots.Why does the gardening business use cuttings and rooting powder to grow new plants?
29Using plant hormones – killing weeds A surprising use of plant hormones is for killing weeds.Why are weeds a problem in farming and gardening?Weeds are unwelcome plants that compete with the plants being grown by gardeners and farmers.Many chemicals that are potential weedkillers are toxicto animals and humans as well as plants.Why might a weedkiller with plant hormones that only affects plants be a more favourable option?
30Using plant hormones – killing weeds Cereal crops like wheat are grasses with narrow leaves.Most weeds that grow in fields and gardens have broad leaves.Selective weedkillers contain plant hormones at concentrations that will only affect plants with broad leaves.What effect will this type of weedkiller have on a field of wheat overgrown with weeds?These selective weedkillers upset the normal growth of broad-leaved plants and so kill off any weeds.The growth of cereal crops and grasses is not affected.
31Using plant hormones – ripening fruit Fruit is usually ripe andready to eat when it isbought from a greengrocersor supermarket.Fruit farmers are able to control when fruit ripensusing plant hormones.Why is this important for their business?Fruit has often travelled many miles before being bought from the shops.Is it better for fruit to be ripe or unripe during a long journey?
32Using plant hormones – ripening fruit Fruit that is picked beforeit is ripe is usually hard.There is less chance of unripe fruit being damaged when transported, whichis important to the farmerand the buyer.Plant hormones can be sprayed onto unripe fruit during transportation. These hormones ripen fruit in time for its arrival in the shops.Why is it a good idea to wash fruit before you eat it?