The plant has the amazing ability to shake its leaves (which rotate on their axis and jerk up and down).

这种植物有着近乎神奇的能力使它的叶片摇动，(叶片围绕其茎轴旋转并上下震摇)。

youdao

She sat up with a jerk.

她猛地坐了起来。

《牛津词典》

I found that 'knee-jerk' reaction curious, so I have a few questions and I'm hoping one of the naysayers will step up and answer them.

我对这种下意识的不假思索的反对颇为好奇，我想提几个问题并且希望这些反对者能够站出来回答这些问题。

youdao

In one, he captures the experience of being from a "jerkwater" town: a village so small that steam-train crews had to "jerk" water up from streams or from people holding buckets along the tracks because there was no water tower from which to refill the engine.

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The pattern has been a steady rise when European news flow is minimal, followed by knee-jerk corrections when the debt crisis flares up.

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Three, should there be any different style of policing, those are questions, they are not knee-jerk reactions because the one thing that I think a grown-up politician doesn't do is just come on the day after and say I've got all the answers because if so it would have been easy enough to do.

BBC: News Online