单项选择题
| Most plants can make their own food
from sunlight, (1) some have discovered that stealing is an
easier way to live, Thousands of plant species get by (2)
photosynthesizing, and over 400 of these species seem to live by
pilfering sugars from an underground (3) of fungi(真菌). But
in (4) a handful of these plants has this modus operandi been
traced to a relatively obscure fungus. To find out how (5)
are (6) , mycologist Martin Bidartondo of the
University of California at Berkeley and his team looked in their roots. What
they found were (7) of a common type of fungus, so
(8) that it is found in nearly 70 percent of all plants. The
presence of this common fungus in these plants not only (9)
at how they survive, says Bidartondo, but also suggests that
many ordinary plants might prosper from a little looting, too. Plants have (10) relations to get what they need to survive. Normal, (11) plants can make their own carbohydrates through photosynthesis, but they still need minerals. Most plants have (12) a symbiotic relationship with a (13) network of what are called mycorrhizal fungi, which lies beneath the forest (14) . The fungi help green plants absorb minerals through their roots, and (15) , the plants normally (16) the fungi with sugars, or carbon. With a number of plants sharing the same fungal web, it was perhaps (17) that a few cheaters—dubbed epiparasites—would evolve to beat the system. (18) , these plants reversed the flow of carbon, (19) it into their roots from the fungi (20) releasing it as "payment." |