2Plant Nutrition How do plants make food? What is photosynthesis? ContentsPlant NutritionHow do plants make food?What is photosynthesis?More about photosynthesisThe rate of photosynthesisMinerals from the soilMultiple-choice quiz
3How do plants get the food they need? All living organisms need food to grow and survive.Plants are known as producers because they provide food for many other organisms.Plants cannot move very much, so how do they get the food that they need?
4Nutrition in green plants Green plants are amazing because they actually make their own food!Green plants are theonly living organisms that are able to do this.All other organisms rely on plants because of the food that the plants make.What is the name of the process by which plantsmake their own food?
5What 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?
6Plant Nutrition How do plants make food? What is photosynthesis? ContentsPlant NutritionHow do plants make food?What is photosynthesis?More about photosynthesisThe rate of photosynthesisMinerals from the soilMultiple-choice quiz
7Photosynthesis: 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
8Photosynthesis: 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
9Photosynthesis: where it happens Plants use light energy from the Sun to power photosynthesis.Where in the leaf does this reaction take place?Photosynthesis takes place in what part of plant cells?light energycarbondioxidewater
10Photosynthesis: where it happens Photosynthesis takes place in plant cellswith 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
11Photosynthesis: products of the reaction The products of the reaction between carbon dioxide and water are glucoseand oxygen.Which of these products is usedby plants?What happens to the ‘waste’ product?lightenergychlorophyllcarbondioxideoxygenglucosewater
12Photosynthesis: products of the reaction 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
13Photosynthesis: 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?
14Photosynthesis: word equation light energycarbondioxidewaterglucoseoxygenchlorophylllightenergychlorophyllcarbondioxideoxygenglucosewater
16Photosynthesis: chemical formulae? Photosynthesis is a chemical reaction involving molecules.glucoselight energychlorophyllcarbondioxidewateroxygenCO2H2OC6H12O6O2The 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?
19Plant Nutrition How do plants make food? What is photosynthesis? ContentsPlant NutritionHow do plants make food?What is photosynthesis?More about photosynthesisThe rate of photosynthesisMinerals from the soilMultiple-choice quiz
20Leaves: maximizing photosynthesis Leaves are the most efficient solar panels on Earth!Why can they be called this?Light energy is absorbedby the chlorophyll in leaves and used to carry out photosynthesis.Leaves come in all shapes and sizes but what features do they have in commonto maximize photosynthesis?
21Structure of a leafHow are leaves designed to maximize photosynthesis?Leaves are wide and flatto create a large surfacearea and to absorbas much light as possible.Leaves are thin so gasescan reach cells easily.Leaves have holes, called stomata, on their underside through which gases move in and out.Leaves have lots of veins to carry water to the cells and carry glucose away.
27Photosynthesis 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?
28Photosynthesis 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?
29Plant Nutrition How do plants make food? What is photosynthesis? ContentsPlant NutritionHow do plants make food?What is photosynthesis?More about photosynthesisThe rate of photosynthesisMinerals from the soilMultiple-choice quiz
30The rate of photosynthesis Photosynthesis is a chemical reaction and so has a rate.Is the rate of photosynthesis always the same?glucoselight energychlorophyllcarbondioxidewateroxygenThe rate of photosynthesis varies depending on three main factors:lightcarbon dioxidetemperatureHow do these factors affect the rate of photosynthesis?
31Light and the rate of photosynthesis Light energy has to be absorbed by chlorophyll for photosynthesis to take place.glucoselight energychlorophyllcarbondioxidewateroxygenThe brighter the light, the more light energy there is,so will photosynthesis be faster or slower?More light energy means that photosynthesis will be faster.If light intensity is too high plant cells can be damaged.How is photosynthesis affected if this happens?
35Carbon dioxide and the rate of photosynthesis Carbon dioxide is one of the raw materials used by plants to make their food.glucoselight energychlorophyllcarbondioxidewateroxygenThe concentration of carbon dioxide in the air (0.03%) is actually quite low.Why is the concentration of carbon dioxide in commercial greenhouses often raised to about 0.1%?More carbon dioxide means more photosynthesis, so plants make more food and grow quicker.
36Temperature and the rate of photosynthesis Photosynthesis is controlled by enzymes.Enzymes usually work best at warmer temperatures.glucoselight energychlorophyllcarbondioxidewateroxygenWhy is the rate of photosynthesis slower on a sunny dayin winter compared to in summer?If the temperature gets too hot (above 40 °C), plant enzymes begin to break down and are destroyed or denatured.Why does photosynthesis stop under such conditions?
37What is a limiting factor? What is the ideal combination of factors for the maximum rate of photosynthesis?enough lightenough carbon dioxideideal temperature (not too hot or cold)How is the rate affected if one of these factors is restricted?If one of the factors is restricted, the rate of photosynthesis will be below the maximum possible rate.The restricted factor controls how quickly photosynthesis occurs and so limits the rate. It is called the limiting factor.
38Photosynthesis and light – limiting factors How does the amount of light affect the rate of photosynthesis on this labelled graph?As the amount of light increases, so does the rate. The limiting factor is light.122Here, increasing the amount of light has no affect on the rate. The limiting factor is now carbon dioxide or temperature.What must be increased for the rate to increase?rate of photosynthesis1light intensity
39Photosynthesis and carbon dioxide – limiting factors How does the amount of carbon dioxide affect the rate of photosynthesis on this labelled graph?1As the amount of carbon dioxide goes up, so does the rate. The limiting factor is carbon dioxide.22Here, increasing the amount of carbon dioxide has no affect on the rate. Light or warmth is now the limiting factor.What must be increased for the rate to increase?rate of photosynthesis1concentration ofcarbon dioxide
40Photosynthesis and temperature – limiting factors How does temperature affect the rate of photosynthesis on this labelled graph?1As temperature increases, so does the rate because photosynthetic enzymes work best in the warmth. Here, the limiting factor is temperature.rate of photosynthesis2Most plant enzymes are destroyed at about 45°C. Here, photosynthesis stops and the rate falls to zero.What is the limiting factor?210oCtemperature45oC
43Plant Nutrition How do plants make food? What is photosynthesis? ContentsPlant NutritionHow do plants make food?What is photosynthesis?More about photosynthesisThe rate of photosynthesisMinerals from the soilMultiple-choice quiz
44What do plants need for a balanced diet? Plants need carbon dioxide and water for photosynthesis.Do they need any other nutrients to keep healthy?Just like humans, plants need a balanced dietthat includes small amounts of mineral elements.What mineral elements do they need?
45What minerals do plants need? Plants need mineral elements for healthy growth.Some of the most important minerals needed by plants are:nitrogennitratesphosphorusphosphatespotassiumpotassium ionsmagnesiummagnesium ionsHow do plants obtain these minerals?The mineral elements are found in salts dissolved in water.Plants obtain minerals when they absorb water from the soil.What type of salt are each of these elements found in?
46What are minerals needed for? How do plants use these mineral elements?Mineral elementHow mineral is used in plantsnitrogen (N)phosphorus (P)potassium (K)magnesium (Mg)making leavesmaking rootsmaking flowers and fruitmaking chlorophyll
48Where do minerals come from? What are the sources of minerals in the soil?Rocks: The minerals in rocks are slowly dissolved by slightly acidic rainwater. These minerals are washed into the soil.Natural fertilizers: Animal faeces and the decay of dead plants and animals return minerals to the soil.Artificial fertilizers: Thesecontain a ready-made mixtureof the minerals needed by plants.Why do farmers add fertilizers to their soil?
49Not enough minerals!What happens if plants do not get enough minerals?Plants do not grow properly if they are deprived of minerals and begin to look unhealthy.If a plant does not get enough of a mineral it is saidto have a mineral deficiency.Do mineral deficiencies affect a plant in the same way?
50Mineral deficiency – no nitrogen! Nitrogen is used for making leaves and is probably the most important mineral for plant growth.What is the effect of nitrogen deficiency?upper leavespale greenlower leaves yellow and deadweak stem
51Mineral deficiency – no phosphorus! Phosphorus is used for making roots and is important for all the other minerals used by plants.What is the effect of phosphorus deficiency?purple leavessmall roots
52Mineral deficiency – no potassium! Potassium is used for making flowers and fruit, so crops are given extra potassium before they start to fruit.What is the effect of potassium deficiency?poor flowerand fruit growthyellow leaveswith dead spots
53Mineral deficiency – no magnesium! Magnesium is used for making chlorophyll and so is vital for the process of photosynthesis.What is the effect of magnesium deficiency?upper leaves normal (leaves turn yellow from bottom upwards)lower leaves pale green or yellow
55Plant and minerals summary Complete this table of plant mineral needs and deficiencies.MineralUse in plantDeficiency signsnitrogenphosphoruspotassiummagnesiummaking leavesstunted growth andyellow leavesmaking rootspoor roots andpurple leavesmaking flowersand fruitsyellow leaves withdead spotsmaking chlorophyllleaves turn yellowfrom the bottom
56Plant Nutrition How do plants make food? What is photosynthesis? ContentsPlant NutritionHow do plants make food?What is photosynthesis?More about photosynthesisThe rate of photosynthesisMinerals from the soilMultiple-choice quiz