hoodia是一种受保护植物，很多专家怀疑，各公司都用其他的同属植物来部分或全部代替hoodia使用。

Hoodia's a protected plant, and many experts suspect that companies replace some or all of it with another species of the same plant.

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但在受火灾保护的实验区，一些多年生草本植物最终占据了主导地位，超过了其他所有植物。

But in experimental areas protected from fire, a few perennial grass species eventually come to dominate, outcompeting all others.

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哈佛大学研究人员认为，这些被称为类胡萝卜素的植物化学物质，可以保护受老化损伤的视网膜。

These plant chemicals, known as carotenoids, protect your retinas from the damage of aging, according to Harvard researchers.

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