This happens when a plant gets attacked by insects.

植物被昆虫攻击时就会发生这种情况。

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Gahn says these findingsare consistent with something called the “plant apparency theory, ”which states that the most readily seen plants are those that are mostlikely to be attacked by predators.

岗恩认为这些发现与有人称之为“植物可见性理论”(plant apparency theory)的解释相一致。 这一理论认为最容易被看到的植物最有可能受到捕食者的攻击。

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On the other hand, when a plant is attacked by an insect, animal or pathogen, it knows.

另一方面，当植物受到昆虫、植物或病菌的侵害时它也知道。

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The crisis started after hostage-takers attacked a gas plant at Tigantourine, near In Amenas, in the Sahara desert on Wednesday 16 January, Algerian officials said.

BBC: Allen McCloud. Pic: AFP

Six British nationals were killed when Islamist militants attacked a BP gas plant in Algeria last month.

BBC: William Hague

Shell's better-than-expected results compared with a 60% plunge in first-quarter profits for Norwegian rival Statoil because of production cuts and operational disruptions after its plant in Algeria was attacked in January.

BBC: Royal Dutch Shell chief executive Peter Voser to retire