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Cereal Crops: Rice, Sorghum and Maize. Nutritive values of cereal crops CropEnergy (kJ/100g) Protein (g/100g) Lipid (g/100g) wheat142012.02.0 rice12968.02.0.

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Presentation on theme: "Cereal Crops: Rice, Sorghum and Maize. Nutritive values of cereal crops CropEnergy (kJ/100g) Protein (g/100g) Lipid (g/100g) wheat142012.02.0 rice12968.02.0."— Presentation transcript:

1 Cereal Crops: Rice, Sorghum and Maize

2 Nutritive values of cereal crops CropEnergy (kJ/100g) Protein (g/100g) Lipid (g/100g) wheat rice maize sorghum potatoes peas lettuce After Inge, Rowland and Baker: A New Introduction of Biology

3 Rice  Rice is grown in paddy fields.  It is adapted for survival in waterlogged conditions. Most plants (including weeds as a bonus) would die in these conditions as they are obligate aerobes.  The roots of rice plants are able to use anaerobic respiration and can tolerate high ethanol concentrations produced as a result.  The stem is hollow, while leaves, stems and roots have air spaces in tissues called aerenchyma. This gives floatation and support and allows oxygen to diffuse through the plant.

4 Cross-section of the stem of a rice plant Hollow centre Air spaces in aerenchyma tissue

5 Maize  Maize is a tropical plant (originally from Mexico area of Central America) adapted for high temperatures, high humidity and high light intensity. (Some varieties have been developed for temperate climates now)  It is adapted to conserve water. The leaves can roll up to reduce exposure of stomata. Stomata are also closed more of the time.  Closed stomata reduce the rate of transpiration, and also reduce uptake of carbon dioxide by diffusion.  Maize must be adapted to overcome these problems:

6 Maize  Maize has evolved a photosynthetic pathway which works well at high temperatures and low CO 2 concentrations (this is the C4 pathway).  Most other plant species use the C3 photosynthetic pathway (C3PO) You don’t have to learn the photosynthetic pathways at AS level!

7 Sorghum  Sorghum is a xerophyte – it is adapted to live in very hot, dry conditions (very important crop in sub- Saharan Africa and the Indian sub-continent). It is adapted to conserve water:  1. Long, extensive root system to reach deep into the soil to find water.  2. Thick waxy cuticle.  3. Few stomata.  4. Sunken stomata to allow water vapour to build up around them – reduces transpiration.  5. Leaves that roll up like maize.  6. It is also adapted to use the C4 pathway.  7. Uses thermostable enzymes.

8 Plenary  Look at the samples of cereal plants grown by the technicians  Draw graphs of photosynthetic rate against light intensity, temperature and carbon dioxide concentration respectively  Relate the adaptations of rice, maize and sorghum to each of these factors


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