题目内容：

    Gardeners may be able to cut down on the amount of weeds(杂草）killer they use by dealing with invaders at specific times of the day, such as dawn, a new study suggests.

Researchers at the University of Bristol have discovered that the 24-hour rhythms of plants leave them more defenseless to herbicides(除草剂) at different points in their daily 24 hour cycle.

They believe the findings could help farmers by reducing crop loss and improving harvests. And gardeners could benefit from knowing which weeds respond better at certain times of the day. In recent years, pesticides and herbicides have been implicated in the decline of important pollinating insects, such as bees.

Dr Antony Dodd，senior author of the new study，said: “The research suggests that, in future, we might be able to improve the use of some chemicals that are used in agriculture by taking advantage of the biological clock in plants.

Just like humans, plants have evolved to take advantage of cycles of night and day, with certain biological processes turning on at different times of the day.

Scientists have discovered that many drugs work much better in humans if they are given at specific hours. Aspirin, for example, has doubled the impact on thinning the blood if taken at night as opposed to in the morning. The process is known as ‘chronotherapy’ and researchers wanted to find out if the same concept could be applied to plants.

Many gardeners already know that plants drink in more water in the morning because their pores(气孔) are open to take advantage of early morning dew and water vapour. At the break of the day, plants are also not busy producing food throughphotosynthesis(光和作用）.The open pores could also be the reasons that chemicals are more effective at dawn and also at dusk.

The air is also likely to be stiller at dawn and dusk, meaning that pesticides or herbicides are less likely to be blown away to places where they are not wanted. Pesticide labels often warn against spraying on windy days in case they endanger people or animals. Many insects are active early in the morning and around dusk, also making very early morning and early evening effective times for insecticide.

Commenting on the study, Dr. Trevor Dines, Botanical Specialist at the conservation charity Plantlife, said: “This is fascinating research which will be of great interest to many gardeners like me. If anything used to think the opposite was true - that applying herbicides and pesticides late in the day would be better as they’d remain in Vet contact' with the plant for longer in the cool of the night and therefore be taken up or absorbed more effectively. This research knocks that assumption on its head”

1.Which of the following can replace the underlined phrase “implicated in” in the third paragraph?

A.restored to B.blamed for

C.limited to D.composed of

2.According to the research, what are the reasons for using herbicides in the morning?

A.The process of photosynthesis is most active in the morning.

B.Insects are more defenseless in the morning than any other time of the day.

C.Bigger pores on the plants make herbicides work more effectively.

D.The stronger morning wind blows pesticides away to more places.

3.What can be inferred from the last paragraph?

A.Gardeners were interested in combining science with gardening.

B.A long time had passed before herbicide was applied in farming.

C.The old assumption about the use of chemicals proved right.

D.Many gardeners used to spray herbicides at the wrong time.

4.What is the main idea of this article?

A.New chemicals have been found to help kill harmful insects.

B.Biological clock of plants could help gardeners use less weed killer.

C.Plants’ cycles can be taken advantage of to improve the environment.

D.The research on the effects of pesticides has enabled good harvests.