Microsoft Word - blank.doc

618 Chapter 18 NEL

Drought-Tolerant and Salt-Tolerant

Plants

Unwise agricultural practices have dramatically reduced the

productivity of the world’s agricultural land. By one estimate,

the reduction in crop yields since 1940 is the same as if all the

land in India and China had produced no crops at all. In

addition, land equivalent to the area of Hungary has become

so degraded that it is unable to produce any viable crop at all.

Much of the problem is linked to poor irrigation techniques

(Figure 9). When water, rich in minerals, floods the land,

evaporation carries away water but leaves the minerals.

Eventually, the mineral salts accumulate within the soil.

creating an environment difficult for plants to survive.

Proposed Solutions from Genetics

Traditionally, plant breeders have used selective breeding to

create new varieties with desirable traits. Today, molecular

biologists have developed gene insertion techniques that

provide breeders with a more precise tool. Using gene

splicing, desired traits from one species can be introduced

into a non-related species.

In 2001, articles in scientific journals reported the

production of genetically modified (GM) tomatoes that can

grow in soils with high salt levels. Researchers inserted a

gene that enhanced the ability of cells in the tomato plants to

transport excess salts into fluid storage sacs (vacuoles). The

GM tomatoes can grow in soils 50 times more saline than

non-GM tomatoes. The salts accumulate in the leaves, so the

tomato fruit does not have a salty taste. The development of

Issue Design Analysis

Resolution Evidence Evaluation

EXPLORE an issue Issue Checklist

Figure 9

Irrigation allows plants to grow in

arid lands.

other plants capable of living in saline solutions will allow

farmers to reclaim marginal land.

In related research, geneticists are looking at developing

drought-tolerant plants. Several genes have been identified

that enable plants to cope with arid conditions. The

Rockefeller Foundation committed $50 million to support the

effort to improve drought resistance for GM maize and rice.

However, as with any technology, GM drought-tolerant and

salt-tolerant plants could have undesirable consequences.

Some of these concerns are outlined below.

Environmental Concerns: Every year, some of the best

farmland in the world is converted to urban land. This

expansion of cities into farmland also reduces food

production. Producing GM drought-tolerant and salt-tolerant

plants that can grow on marginal land does nothing to resolve

the issue of urban expansion.

GM drought-tolerant and salt-tolerant plants could lead to

the conversion of deserts and saltwater marshes into

agricultural land, disrupting the natural balance within these

ecosystems. These ecosystems provide habitat for many

species, and saltwater marshes also help filter and clean

water systems.

Food Production Concerns: At present, 5 billion people

inhabit Earth, and the population is projected to increase to

nearly 10 billion within 50 years. Only 3.7 billion ha (hectares)

of the world’s 13.1 billion ha of land can be used for crop

production. According to the United Nations Food and