The lecturer argues that the three theories about the plants folding up their leaves mentioned in the reading passage are not acceptible. The three theories were that plants fold up their leaves in order to protect their pollen, to lessen the amount of water they lose during nights, and not to let animals to eat them.
First, the lecturer says that the first theory is insufficient to explain the reason why plants fold their leaves up. Since there are non-flowering plants, which does not have pollen and still fold their leaves up, the first theory that plants fold their leaves in order to keep pollen safe from the moisture does not make sense.
Second, the lecturer insists that the second theory is not true. He mentions that there are aquatic plants which is in the environment abundant of water but still is folding up their leaves during the night. This contradicts reading passage's claim that plants fold their leaves up to prevent their water from being evaporated.
Lastly, the lecturer does not agree with the third theory in the reading passage. He says that nocturnal herbivores find their preys by smell not by sight. Besides, he argues that even if the plants fold up their leaves, the size does not get much smaller, and the animals can still recognize them. This refutes the reading passage's claim that the plants fold their leaves up because they believe doing that will lessen the possibility of being eaten by nocturnal animals by making themselves less attractive and smaller.
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