1 . How Gardeners Can Reduce Risk of Fire

If you are selecting plants for your garden, knowing which plants offer some fire resistance and which are more flammable (易燃的) can serve you well.

Quicker to catch fire

Plants like bamboo that produce flammable substances such as aromatic oils, resins (树脂), wax, or sap, are among the quickest to catch fire.     1    

Trees with thin bark (树皮) that falls off are usually more flammable than those without. And fine-needled plants like pine, juniper, and spruce contain resins.     2    

Many kinds of grasses are highly flammable. Their ability to catch fire increases when they are left to stand dry over winter or during periods without rain. Additionally, too much heat dries out the soil and under such conditions, many kinds of plants turn into a fire starter.

Native vs. non-native

As a group, native plants aren’t necessarily less flammable than introduced kinds of plants.     3     That is because they spread quickly and are usually left alone by wildlife. The non-native plants spread faster than native plants, and often tolerate heat, heavy rain and lack of water better.

For the best fire resistance, choose trees that lose their leaves every year, like ash, and maple, rather than fine-needled trees.     4     Those plants with water-filled leaves include ice plants and sedums. Some groundcover plants are also slow burners.

What to look for in plants

The Washington State University Extension Service has published advice for choosing plants that are fire-resistant.     5     They include:

•High water content in leaves.

•Little or no seasonal gain of dead plant material.

•Open branching (they provide less fuel for fires).

•Fewer total branches and leaves.

A．Some plants are more flammable than others.

B．Plants with water-filled leaves are slow to burn.

C．But non-native plants often are a greater fire risk.

D．Many plants have qualities that do not burn easily.

E．All plants might catch fire under the right conditions.

F．Their needle-like leaves increase the risk of fire when left on the ground.

G．They will often catch fire even if they have been well-watered and cared for.

2 . Common water plant could provide a green energy source. Scientists have figured out how to get large amounts of oil from duckweed, one of nature’s fastest-growing water plants. Transferring such plant oil into biodiesel (生物柴油) for transportation and heating could be a big part of a more sustainable future.

For a new study, researchers genetically engineered duckweed plants to produce seven times more oil per acre than soybeans. John Shanklin, a biochemist says further research could double the engineered duckweed’s oil output in the next few years.

Unlike fossil fuels, which form underground, biofuels can be refreshed faster than they are used. Fuels made from new and used vegetable oils, animal fat and seaweed can have a lower carbon footprint than fossil fuels do, but there has been a recent negative view against them. This is partly because so many crops now go into energy production rather than food; biofuels take up more than 100 million acres of the world’s agricultural land.

Duckweed, common on every continent but Antarctica, is among the world’s most productive plants, and the researchers suggest it could be a game-changing renewable energy source for three key reasons. First, it grows readily in water, so it wouldn’t compete with food crops for agricultural land. Second, duckweed can grow fast in agricultural pollution released into the water. Third, Shanklin and his team found a way to avoid a major biotechnological barrier: For the new study, Shanklin says, the researchers added an oil-producing gene, “turning it on like a light switch”by introducing a particular molecule (分子) only when the plant had finished growing. Shanklin says, “If it replicates (复制) in other species-and there’s no reason to think that it would not — this can solve one of our biggest issues, which is how we can make more oil in more plants without negatively affecting growth.”

To expand production to industrial levels, scientists will need to design and produce large-scale bases for growing engineered plants and obtaining oil — a challenge, Shanklin says, because duckweed is a non-mainstream crop without much existing infrastructure (基础设施).

1. What can people get from duckweed firsthand?

A．Plant oil.	B．Stable biodiesel.
C．Sustainable water.	D．Natural heat.

2. What does paragraph 4 mainly convey?

A．Options for renewable energy.

B．Reasons for engineering genes.

C．The potential of revolutionary energy source.

D．The approach to avoiding agricultural pollution.

3. What is the decisive factor to mass-produce the plant?

A．Industrial levels.	B．Unique design.
C．Academic research.	D．Basic facilities.

4. What would be the best title for the text?

A．Duckweed Power	B．Duckweed Production
C．Genetic Engineering	D．Genetic Testing

3 . When gardeners grow varieties of plants in their beautiful gardens, they are happy to see beneficial insects like bees and butterflies surrounding the flowers. But as they take a closer look, they may find some plants are covered in black dots and filled with harmful insects or pests. Some gardeners may immediately reach for chemicals.     1     Although it may stop the insect problem, it will also threaten bees and butterflies which help the plants reproduce.

If you are wise gardeners, you should first take preventive measures to control the harmful insects.     2     Only when there are too many harmful insects, should pest control be considered. The first defense should always be the safest method available.

Prevention

As a rule, prevention is the best treatment. Inspect plants closely, including their leaves, before buying them from the store.     3    

When planting, space plants out to permit them to grow to their full size. Plants too close together can breed harmful organisms, like bacteria.

    4     They invite pests if permitted to remain on the ground. When you do see pests, wash them away. Use rubbing alcohol to remove some insects, or pick them off the plants.

Pesticides

If you decide a pesticide is necessary, choose it carefully and follow the directions and warnings on the product. Avoid using pesticides in extreme heat, on windy days, or when the plants are wet.     5     At the time, beneficial insects are inactive. You can consider removing flowers from the plants to lessen the risk that beneficial insects will come in contact with the pesticides.

A．But this is not wise.

B．In most cases, chemicals don’t help.

C．Treat the plants early in the morning or at night.

D．Also do remember the plants need nutrition and care.

E．Keep your garden free of fallen leaves, fruits and other wastes.

F．Do not bring any plants home that show signs of disease or pests.

G．The process starts with the idea that having some pests is acceptable.