Chapter 1, Section 2

Chapter 1, Section 2

Agriculture

The world’s population is increasing, but the amount of land available to grow food is decreasing. Land that was once used for agriculture is now used for homes and industries. So it is important to ensure that land used for agriculture is as productive as possible. Chemists help to develop more productive crops and safer, more effective ways to protect crops.

Productivity

One way to track productivity is to measure the amount of edible food that is grown on a given unit of land. Some factors that decrease productivity are poor soil quality, lack of water, weeds, plant diseases, and pests that eat crops. Chemists can help with many of these problems. They test soil to see if it contains the right chemicals to grow a particular crop and recommend ways to improve the soil. They use biotechnology to develop plants that are more likely to survive a drought or insect attack.

Chemists can also help to conserve water. In many regions, water is not an abundant resource. Finding reliable ways to determine when a crop needs water is important. The jellyfish in Figure 1.10 has a gene that causes it to glow. If that gene is inserted into a potato plant, the plant glows when it needs to be watered. These altered plants would be removed from the field before the rest of the crop was harvested.

Figure 1.10 If genes from this jellyfish (Aequaria victoria) are transferred to a potato plant, the plant glows when it needs to be watered. Predicting How does the modified plant help a farmer to conserve water?

Crop Protection

For years, farmers have used chemicals to attack insect pests. In the past, these chemicals were nonspecific; that is, a chemical designed to kill a pest could also kill useful insects. Today, the trend is toward chemicals that are designed to treat specific problems. These chemicals are often similar to the chemicals that plants produce for protection.

Chemists sometimes use chemicals produced by insects to fight insect pests. Female insects may produce chemicals that attract male insects. This type of chemical has proved effective in combating pinworms. The worms leave holes and black blotches when they tunnel into tomatoes. Pinworms mate when they are in the moth stage of development. The plastic tube wrapped around the stem of the tomato plant in Figure 1.11 contains the chemical that a female pinworm moth emits to attract male moths. When the chemical is released from these tubes, it interferes with the mating process so that fewer pinworms are produced.

Figure 1.11 In the plastic tube wrapped around the tomato stem, there is a chemical that attracts male pinworm moths. This process reduces the rate of mating between female and male moths, and the number of pinworms produced.