Cereals and Crop Plants

A crop plant is one that humans grow for a specific purpose. Cereals are crops that are grown for their grain. They include:

Rice -Maize - Sorghum

Each are grown in different conditions and have specific requirements.


Rice

• CONDITIONS: warm swamps.
• PROBLEM: waterlogged soil with low oxygen concentration.
• SOLUTIONS:

1. Rice respires anaerobically producing ethanol. Plant tissue is tollerant of high concentrations.
2. Stems contain aerenchyma. These allow oxygen diffusion to the roots, enabling aerobic respiration. They also provide buoyancy keeping photosynthesising leaves near the light.

Maize

• CONDITIONS: Hot
• PROBLEM: Stomatas close preventing water loss, BUT CO2 cannot enter the plant
• SOLUTIONS:

1. C4 Pathway allows plant to take in CO2 at low concentrations, and photosynthesise using a 4-C compound. This uses lots of ATP and so occurs in high light intensities.

SORGHUM-A Xerophyte

• CONDITION: Hot and Dry
• PROBLEM: Water Loss
• SOLUTIONS: increase water uptake and reduce water loss.

1. Extensive root system enables uptake over a large area of soil
2. Thick waxy cuticle on upper surface of leaf reduced water evaporation
3. Very few stomata in the leaf
4. Leaves roll inwards in dry conditions to trapping a layer of moist air
5. Tollerant of high temperatures