It is easy for us to tell who our family members are, but do plants recognize(识别) their own family? Some do, scientists say, according to a report by Science News in early 2010.
Guillermo P. Murphy and Susan Dudley are two plant scientists from McMaster University in Hamilton, Canada. They did a few experiments with Jewelweeds, a kind of flower that grows in wet, shady spots. They found that the flowers seem to know their own flower family. In their experiments, Murphy and Dudley planted jewelweeds in pots with either siblings or strangers.
When jewelweeds were planted in pots with strangers, the plants started to grow more leaves than if they had been planted alone. This response(反应)suggests that plants are competing with strangers for sunlight, since a plant with more leaves can receive more light and make more food. Jewelweeds usually grow in the shade, where sunlight is not enough.
When jewelweed seedlings(幼苗)were planted with siblings, they grew a few more branches than they usually would if they were alone – but they did not start growing lots of extra leaves. This behavior suggests the plants are more likely to share resources, rather than compete.
According to the Science News report, Jewelweeds are not the first plants that plant scientists have studied for family recognition. In 2007, Dudley and her team studied the Great Lakes sea rocket, a plant that grows on the beach – where it may be hard to get fresh water. In that experiment, the scientists found that when sea rockets were planted with siblings, they tolerated each other. But when they were planted with strangers, the sea rockets reacted by working extra hard to grow lots of roots.
Dudley says this just because sea rockets, on the beach, get plenty of sun but struggle for water – so when they’re threatened, they compete for water. Jewelweeds have plenty of water but have to compete for sunshine, so they grow more leaves.
【小题1】 What does the underlined word siblings mean?

How old is “old”? The answer has changed over the years. Two Hundred years ago, you were old at 35. At the beginning of the 20th century, the average life span (平均寿命) was 45. In 1950, 70-year-olds were really old. Today, a healthy 70-year-old is still thought young.

          So, how old is “old”? The answer is one you’ve heard many times, from all kinds of people. “You are as old (or young) as you feel.” Your age simply tells you how many years you have lived. Your body tells you how well you’ve lived.

         “Nobody grows old by living a number of years,” wrote a writer. “People grow old when they don’t have their ideals (理想).” People shouldn’t have the wrong ideas about aging. Sometimes, older minds can be as bright as young minds. Alice Brophy once said, “It makes me unhappy when people say, ‘You look young for your age.’ What does that mean? You know you can die old at 30 and live young at 80.”

1.About 100 years ago, the average life span was __________.

A. 35                   B. 45    C. 70  D. 80

2. The meaning of the word “aging” is __________.

A. growing old     B. staying young    C. keeping healthy                  D. feeling unhappy

3.According to the passage, which of the following is true?

A. Old people are not as bright at young people.      

B. All older people are healthy and strong.

C. Aging does not mean you become unhealthy.       

D. Most older people are unhealthy and poor.

4. The passage is mainly(主要地) about _________.

A. the average life span              B. aging

C. the 20th century                     D. older people and young people

It is easy for us to tell who our family members are, but do plants recognize(识别) their own family? Some do, scientists say, according to a report by Science News in early 2010.

Guillermo P. Murphy and Susan Dudley are two plant scientists from McMaster University in Hamilton, Canada. They did a few experiments with Jewelweeds, a kind of flower that grows in wet, shady spots. They found that the flowers seem to know their own flower family. In their experiments, Murphy and Dudley planted jewelweeds in pots with either siblings or strangers.

When jewelweeds were planted in pots with strangers, the plants started to grow more leaves than if they had been planted alone. This response(反应)suggests that plants are competing with strangers for sunlight, since a plant with more leaves can receive more light and make more food. Jewelweeds usually grow in the shade, where sunlight is not enough.

When jewelweed seedlings(幼苗)were planted with siblings, they grew a few more branches than they usually would if they were alone – but they did not start growing lots of extra leaves. This behavior suggests the plants are more likely to share resources, rather than compete.

According to the Science News report, Jewelweeds are not the first plants that plant scientists have studied for family recognition. In 2007, Dudley and her team studied the Great Lakes sea rocket, a plant that grows on the beach – where it may be hard to get fresh water. In that experiment, the scientists found that when sea rockets were planted with siblings, they tolerated each other. But when they were planted with strangers, the sea rockets reacted by working extra hard to grow lots of roots.

Dudley says this just because sea rockets, on the beach, get plenty of sun but struggle for water – so when they’re threatened, they compete for water. Jewelweeds have plenty of water but have to compete for sunshine, so they grow more leaves.

1. What does the underlined word siblings mean?

A．Flowers come from foreign countries.

B．Plants growing in different environments.

C．Flowers planted with lots of strangers.

D．Plants that are the same kind.

2. In the text, the writer mentioned the experiments of Jewelweeds to         .

A．make a comparison                      B．introduce a topic

C．describe a pretty flower                  D．build a new theory

3. According to the passage, flowers planted alone will         .

A．grow more leaves than those planted in groups

B．become taller than those with more branches

C．grow fewer leaves than those planted with strangers

D．become ill easily because they can’t get enough shade

4. What can be the best title for the passage?

A．New Discoveries about Plants

B．How Plants Compete with Each Other

C．Family Recognition among Plants

D．Jewelweeds and the Great Lakes Sea Rockets