Narrator: Listen to part of a lecture in a biology class. Professor: Today we're going to talk about a fascinating adaptation in desert plants: the phenomenon of 'hydraulic lift.' Some plants, like the mesquite tree, have deep roots that tap into groundwater. At night, when the leaves are not photosynthesizing, these roots absorb water and transport it upward. But instead of keeping all this water, the plant releases some of it through its shallow roots into the drier upper soil layers. This process, discovered in the 1980s, benefits not only the tree itself but also neighboring plants. The water released at night can be taken up by the shallow roots of surrounding grasses and shrubs the next day. Interestingly, hydraulic lift is most active during dry periods, when the moisture difference between deep and shallow soil is greatest. However, it stops if the upper soil becomes too wet. This adaptation highlights the interconnectedness of species in arid ecosystems, where water is a precious resource.
❓ 题目 According to the professor, what is a key characteristic of hydraulic lift in desert plants?
A. A. It occurs mainly during the day when photosynthesis is active.
B. B. It releases water from deep roots into the upper soil at night.
C. C. It prevents neighboring plants from accessing water.
D. D. It only happens when the upper soil is saturated with water.
✅ 正确答案
B. It releases water from deep roots into the upper soil at night.