Growing Crops

This Salters’ Science extension module for biology deals with the breeding, cultivation and harvesting of plants as crops. Experiments on soil structure and nutrient content are matched with data about major crops to show why different crops require different conditions for growth. Controlled environments such as glasshouses are linked to the efficiency of photosynthesis. Annual, biennial and perennial life cycles are compared. Fruit and seed structure, pollination and seed dispersal are studied. Grafting of plants is studied. Adaptations which allow weeds to flourish are considered using experiments on the growth of couch grass. Use of genetic engineering to develop crop species resistant to herbicides is studied. The world importance of cereal crops, and problems associated with establishing new species is related to issues of world food supply.

Lesson 1: Does it matter what we grow?
Students discuss the scale and variety of agricultural activity and the choice of crops. They carry out experiments on soil particle size, acidity and nutrient content.

Lesson 2: Does farming pay?
Small group text-based exercises gathering information about different crops and presenting findings.

Lesson 3: Controlling Growth.
Students plan and set up an extended investigation of factors which control plant growth. They consider controlled environments such as glasshouses.

Lesson 4: This year, next year?
The different parts of plants are considered in relation to their use as crops. Annual, biennial and perennial life cycles are described and the structure of cereal flowers and apple flowers is examined.

Lesson 5: Fruits of their labour
A series of diagrams shows the stages in pollination and how the structure of seeds is related to their method of disposal.

Lesson 6: Fruit engineering
An open-ended investigation into the behaviour of wind-dispersed fruit.

Lesson 7: An apple a day!
Experiments in grafting tomato stems onto potato root stock. Text exercises on the production of apples with different numbers of chromosomes.

Lesson 8: Weeding out
The problems caused by weeds are considered. Adaptations which help weeds to become rapidly established are considered. Experiments to show how couch grass can survive different weed clearing procedures. Use of genetic engineering to develop herbicide resistant crop plants.

Lesson 9: Making the grasses greener
A card-gane simulation to illustrate the use of selective breeding to improve crop species, especially cereals. Discussion of the problems of introducing new selectively bred plants, especially in developing countries.