What factors affect plant growth?
LO- to explain the factors which affect plant growth What factors affect plant growth?
LO- to explain the factors which affect plant growth Green plants absorb light energy using chlorophyll in their leaves. They use it to react carbon dioxide with water to make a sugar called glucose. The glucose is used in respiration, or converted into starch and stored. Oxygen is produced as a by-product. During photosynthesis:
Light energy is absorbed by chlorophyll, a green substance found in chloroplasts in some plant cells and algae Absorbed light energy is used to convert carbon dioxide (from the air) and water (from the soil) into a sugar called glucose Oxygen is released as a by-product This equation summarises what happens in photosynthesis: Some glucose is used for respiration, while some is converted into insoluble starch for storage. The stored starch can later be turned back into glucose and used in respiration. Without enough light, a plant cannot photosynthesise very quickly, even if there is plenty of water and carbon dioxide. Increasing the light intensity will boost the speed of photosynthesis. Sometimes photosynthesis is limited by the concentration of carbon dioxide in the air. Even if there is plenty of light, a plant cannot photosynthesise if there is insufficient carbon dioxide If it gets too cold, the rate of photosynthesis will decrease. Plants cannot photosynthesise if it gets too hot. If you plot the rate of photosynthesis against the levels of these three limiting factors, you get graphs like the ones above. In practice, any one of these factors could limit the rate of photosynthesis. Storage & Use Of Glucose
The glucose produced in photosynthesis may be used in various ways by plants and algae. Storage Glucose is needed by cells for respiration. However, it is not produced at night when it is too dark for photosynthesis to happen. Plants and algae store glucose as insoluble products. These include: Starch Fats and oils Use Some glucose is used for respiration to release energy. Some is used to produce: Cellulose - which strengthens the cell wall Proteins - such as enzymes and chlorophyll Plant nutrients Plants need nutrients to stay healthy and grow. The most common type of fertilisers used contain NPK N- nitrogen P- phosphorous K- potassium fertilisers contain minerals such as:
nitrates which are needed to makeproteins. Proteins are needed for cell growth phosphates for respiration and growth potassium compounds for respiration and Photosynthesis magnesium compounds for photosynthesis. mineral deficiencies to the resulting poor plant growth:
nitrate poor growth and yellow leaves phosphate poor root growth and discoloured leaves potassium poor flower and fruit growth and discoloured leaves magnesium yellow leaves. Nitrogen is needed for plant growth as it is used to make proteins, too little nitrogen and the plant will have stunned growth, too much then the plant will grow too quickly, become long and spindly and then will be prone to wind damage. Phosphate is needed for respiration and growth of the plant, without it plants will have yellow leaves and the roots will grow slowly Potassium is needed for respiration and photosynthesis ( its is used to make the enzymes used in these processes), without it the leaves will turn yellow/brown at the edges and the plant will have less flowers and fruit Magnesium makes the compounds needed for photosynthesis, without it the plant will have yellow leaves and less crops will be produced Nutrients get into the plant through the roots, they dissolve in water to make soil solution, the nutrients travel through the plant in the xylem Fertilisers-substance added to the soil to improve plant growth
Organic fertiliser- a natural substance such as manure, bone meal and wood ash Inorganic fertiliser-chemicals made with the right balance of each nutrient Organic fertilisers Inorganic fertilisers Signs of a unhealthy plant.
Wilting- the cells are flaccid Slug snails and fungi on the plants Explain why plant nutrients are important and the problems the plant may have if they do not have enough nutrients What factors affect plant growth?
LO- to explain the factors which affect plant growth Economics Of Greenhouse
Farmers can use their knowledge of factors limiting the rate of photosynthesis to increase crop yields. This is particularly true in greenhouses, where the conditions are more easily controlled than in the open air outside: The use of artificial light allows photosynthesis to continue beyond daylight hours. Bright lights also provide a higher-than-normal light intensity. The use of artificial heating allows photosynthesis to continue at an increased rate. The use of additional carbon dioxide released into the atmosphere inside the greenhouse also allows photosynthesis to continue at an increased rate. Paraffin lamps have traditionally been used in greenhouses. Their use increases the rate of photosynthesis because as well as the light generated from the lamps, the burning paraffin produces heat and carbon dioxide too. Pollination is the transfer of pollen from the anther to the sigma, this is needed for fertilisation. There are two main ways for pollen to be transferred; by insects and by the wind Insect or wind pollination? Cross pollination is the transfer of pollen from one plant to another
Cross pollination is the transfer of pollen from one plant to another. This is done to increase the gene pool. To stop self- pollination some plants are dioecious which means that male and female parts are on different flowers. Anthers and stigma may mature at different times on some plants. A seed contains everything a plant needs to grow
A seed contains everything a plant needs to grow. It contains enough food for the plant till it gets to a stage where the plant can photosynthesise The testa protects the seed from attacks by insects
The micropyle is a small hole inside thetesta which allows water into the seed, this will cause is to swell and split the testa- ready for germination The cotyledons form the first two leaves of the plant The pulmule forms the roots when a plant germinates, and the radicle forms the shoots To germinate, plants need water, oxygen and the correct temperature
To germinate, plants need water, oxygen and the correct temperature. oxygen is needed for respiration to provide the energy needed for growth Seeds are said to be dormant before they germinate Breeding Plants Look at this list of characteristics of strawberry plants. Plants will not die in temperatures below 4C Strawberries rot quickly strawberries stay fresh for a week after picking Big strawberries Plants produce lots of strawberries Plants are resistant to disease strawberries are bright red strawberries are very tasty strawberries are juicy Small strawberries Plants can survive with little water. Plants have small leaves Which characteristics are important to:a) A farmer, b) A shopper? If you were a plant breeder, which 5 characteristics would you like your new variety of strawberries to have?Explain your choices. What is selective breeding and genetically modified food?
LO- to explain the advantages and disadvantages of selective breeding and GM food Selective breeding is the process where plants or animals are breed for a chosen characteristicthey can be selectively bred to improve yield, resistance to disease and climate, taste and appearance When two different species are crossed a hybrid is produced
Hybrid vigour is when characteristic in the offspring have improved from the characteristic in from the parents Genetic engineering allows use to put a gene from one organism into another organism to give it new characteristics For example a gene from a fish which can live in cold seas can be put into tomato plants to allow it to survive in cold climates. GE could also be used to kill weeds People worry as they we do not know the consequences of eating genetically modified food and we do not know what it will do to the environment Will these genes be transferred to weeds? What will happen to the biodiversity? Task- create a farm which is pro selective breeding and genetically modified food:
what characteristics have the plant been selected for? What are the advantages and disadvantages of selectively breeding of plants? How could you use selective breeding to increase crop yields? How could you improve crop by genetic engineering? Inside the nucleus of a cell we find our DNA
Inside the nucleus of a cell we find our DNA. A gene is a section of DNA which codes for a trait (eg hair colour, eye colour). Genes are grouped together in chromosomes. The genetic make up of an organism is called its genotypes. Thereare two genes for each characteristic/trait. The organisms phenotype is the characteristics/trait we see. Different copies of the same gene are called alleles
Different copies of the same gene are called alleles. Alleles may be dominant or recessive. Dominant alleles are always expressed over recessive alleles. Monohybrid inheritance
When the F1 generation was crossed with F1 generation (e. g
When the F1 generation was crossed with F1 generation (e.g. round seed(F1) & round seed(F1) crossed), both round and wrinkled seeds were produced. This tell us about that traits are determined by two different allelles, one dominant and one recessive. We cultivate soil to make it ready to grow crops
We cultivate soil to make it ready to grow crops. We remove weeds and improve the soil structure. In autumn we fork the soil to loosen it up. This allows air in and allows the soil to break down due to frost. We out trenches into clay soil to increase the surface area which allows weathering to break up the soil and the soil to aerate as water can drain out more easily. Single Digging aerates the soil removes weeds improves drainage FYM can be added to improve crumb structure raked to produce a good tilth Soil crumbs are formed from inorganic soil particles sand, silt and clay, are held together by humus. A good soil crumb is important to allow the soil to be aerated, retain moisture and nutrients and allow the water to drain. If the soil is too dense the roots will find it difficult to grow and the soil will become water logged, if it is too sandy it will drain too easily washing away the nutrients and the structure will not support the plants. We can improve the soil fertility by adding humus, compost or well rotted manure to the soil, they are all rich in nutrients especially nitrates. They will release nutrients over a period of time. Clay Water Humus Sand Silt Lime can be added to clay soil, it causes the soil to flocculate which means it sticks together to allow the soil to aerate and drain. It is also an alkali so can neutralise acidic soil. Sand can be added if you need to drain clay soil very quickly but can make it heavier. Storing Crops Ripening Bruising Diseases Pests A problem with storing food is their perishability- the likely hood they will spoil or decay. This is caused by the growth of fungi, moulds and bacteria on the crop. Pest and disease are another problem, rats and mice will invade barns which contain stores of food. Animal pests will bring disease. Managing pests Loweringthe temperature of stored food will stop pest beingable to survive which will prolong the life of the food. Respiration is reduced at lower temperatures. The atmosphere can be controlled so there is not enough oxygen for organisms to survive Fruit is normally picked before it is ripen and the gas ethylene is used to ripen the fruit