試題詳解

40. If a complete ring of bark is removed from around a tree trunk (a technique called girdling), the tree will die, but typically slowly (in weeks) rather than quickly (in days). Which of the following best explains this observed timeframe?
(A) Girdling only disrupts the xylem, and the tree's roots can store enough water to survive for a few days.
(B) Girdling severs the phloem, cutting off sugar transport to the roots, which leads to root starvation and eventual death, a process that takes weeks.
(C) Girdling directly kills all the living cells in the trunk, but the leaves can continue photosynthesis until stored carbohydrates are depleted.
(D) The tree can regenerate the phloem within days, thus preventing rapid death, but the energy cost is high.