In the wild they eat seeds from thistles, dandelions, sunflowers, and ragweed.

而在野外，它们吃蓟，蒲公英，向日葵和豚草的种子。

And if you have allergies, ragweed is a bad plant.

如果你出现过敏，那豚草就是坏植物。

Ragweed is a common allergen, especially during the fall.

豚草是一种常见的过敏原，秋天时尤为常见。

Increased carbon dioxide in the air may also lead to ragweed pollen that is stronger, or more allergenic.

空气中二氧化碳增多还可以使豚草花粉变得更强，或更具过敏性。

Ziska said that ragweed is one of the plants that has the most effect on human health.

杰斯卡表示，豚草是对人类健康影响最大的植物之一。

The researchers grew ragweed in a controlled environment and increased the carbon dioxide levels in the air.

研究人员在受控环境中种植了豚草，同时增加了空气中的二氧化碳浓度。

They found that ragweed plants produced much more pollen when carbon dioxide levels increased.

他们发现，二氧化碳浓度增加时，豚草产生了更多花粉。

And one of the plants that has a(n) effect in terms of human health is ragweed. It's the most common allergen in the fall.

而对人类健康有影响的其中一种植物就是豚草。豚草是秋天最为常见的过敏原。"

He and another USDA researcher, Frances Caulfield, looked at the effects that rising carbon dioxide levels were having on the production of ragweed pollen.

他和美国农业部研究员弗朗西斯·考菲尔德研究了上升的二氧化碳水平对豚草花粉产量的影响。