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Cereal Crops presentation

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Cereal Crops

Rice, Maize and Sorghum

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

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

Rice

Rice

Grown in areas of high temperature and high humiditySmall 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

Adaptations of rice to water logging

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

Sorghum

This 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

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

Adaptations 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

Adaptations 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

C3 and C4 photosynthesis

In 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

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

And finally Maize

Another 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