2 Cereals- the worlds staple foods Cereals are all members of the grass familyExamples include rice, wheat, maize and sorghumThey are grown for their seeds (grains) which are high in carbohydrates and proteinThe water content of the grains is low compared to other vegetables
3 Other benefits of cereals Easy to store because the low water content helps prevent mould growthEasy to transport because there is not a lot of wet bulkThere is a suitable cereal for each type of climate
5 Rice Grown in areas of high temperature and high humidity Small plants are planted out in flooded fieldsRice can grow in normal soilFlooded fields reduce competition from weedsNitrogen fixing bacteria live on flooded rice roots providing nitrate. This reduces need for fertiliser
6 Adaptions of rice to waterlogging Roots contain air spaces to conduct oxygen from the air down into the roots. This tissue is called aerenchymaRoot cells are tolerant of ethanol which is the waste product from anaerobic respiration by root cells when oxygen is lacking
7 SorghumThis is a cereal which is adapted to grow in arid (dry) regions and tolerate high temperatures and light intensitiesUses a quarter of the water needed by riceHas a lower grain yield than cereals grown in areas where water is abundant but is often the only crop that will grow
8 Adaptions of sorghum to drought Extensive root systemThick cuticle (waxy layer covering leaves) reduces evaporation of water from leavesSunken stomata reduce water loss by evaporationStomata close during drought and reopen very quickly afterwards
9 Adaptions of Sorghum to heat Sorghum plants can synthesis heat shock proteins rapidly when temperatures riseThese heat shock proteins prevent enzymes being denatured and make them more thermostable
10 Adaptions of sorghum to high light intensity Sorghum plants carry out C4 photosynthesisThis means that when carbon dioxide is absorbed into leaf cells it combines with molecules in the cells to make a molecule containing 4 carbon atoms
11 C3 and C4 photosynthesisIn temperate regions like the UK most plants are C3This means that the first molecule made when CO2 enters the leaf cells has 3 carbon atomsC4 photosynthesis is an advantage to plants in hot regions with high light intensity
12 Advantages of C4 photosynthesis A different enzyme is used. C3 plants use the enzyme rubisco which is not very effective when CO2 concentrations in the leaf cells are relatively low.C4 plants use the enzyme PEP this enzyme has a high affinity for CO2 even when concentrations are low, for example when plants close their stomata to reduce water loss
13 And finally MaizeAnother C4 plant which is able to photosynthesis efficiently at high temperatures and light intensities.Needs more water than sorghum but gives a higher yield so the preferred crop wherever there is enough rainfall
14 This powerpoint was kindly donated to www.worldofteaching.com is home to over a thousand powerpoints submitted by teachers. This is a completely free site and requires no registration. Please visit and I hope it will help in your teaching.
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