6.Leaves that had been exposed had significantly higher levels of defensive chemicals like glucosinolates and anthocyanins, making them much harder for the caterpillars to eat.
7.That something could be anthocyanin, or it could be a dangerous toxin, but the knob itself isn't the problem, nor is the process by which it was added.
9.The skin of grapes is a rich source of antioxidants, including resveratrol, anthocyanins, and flavonoids. These compounds are known for their ability to fight oxidative stress and reduce inflammation in the body.
10.But it is hard to make sense of the manufacture of anthocyanins—why should a tree bother making new chemicals in its leaves when it's already scrambling to withdraw and preserve the ones already there?
11.F Perhaps the most plausible suggestion as to why leaves would go to the trouble of making anthocyanins when they're busy packing up for the winter is the theory known as the 'light screen' hypothesis.
F 关于为什么叶子在忙于收拾过冬时会费力制造花青素,也许最合理的建议是被称为“光屏”假说的理论。机翻
12.D Some theories about anthocyanins have argued that they might act as a chemical defence against attacks by insects or fungi, or that they might attract fruit-eating birds or increase a leaf's tolerance to freezing.
D 一些关于花青素的理论认为,它们可能作为一种化学防御剂来抵御昆虫或真菌的攻击,或者它们可能会吸引食果鸟类或增加叶子的抗冻能力。机翻
13.However there are problems with each of these theories, including the fact that leaves are red for such a relatively short period that the expense of energy needed to manufacture the anthocyanins would outweigh any anti-fungal or anti-herbivore activity achieved.