Directions: Fill in each blank with a proper word chosen from the box. Each word can only be used once. Note that there is one word more than you need.

Extreme conditions produce extremely tough plants. The big difference between "drought—tolerant" plants and these tough plants: metabolism. Many different kinds of plants have developed tactics to weather dry spells. Some plantsof water to see them through a drought; others send roots deep down to subsurface water supplies. But once these plants use up their stored water or tap out the underground supply, they cease growing and start to die. They may be able to handle a drought of some length, and many people use the term "drought tolerant" to describe such plants, but they never actually stop needing towater, so Farrant prefers to call them drought.

Resurrection plants, defined as those capable of recovering from holding less than 0. 1 grams of water per gram of dry mass, are different. They lack water—storing structures, and their existence on rock faces prevents them fromgroundwater, so they instead developed the ability to change their metabolism. When they detect a/andry period, they change their metabolisms, producing sugars and certain stress—proteins and other materials in their tissues. As the plant dries, these resources take on first theof honey, then rubber, and finally enter a glass—like state that is "the most stable state that the plant can maintain, " Farrant says. Thatthe plant's metabolism and protects its dried—out tissues. The plants also change shape, shrinking to minimize the surface area through which their remaining water might evaporate. They can recover from months and years without water, depending on the species.

What else can do this dry—out—and—revive trick? Seeds—almost all of them. At the start of her career, Farrant studied seeds such as avocados(牛油果) , coffee and lychee(荔枝). Though, such seeds are delicate — they cannot bud and grow if they dry out. Most seeds can wait out the dry, unwelcoming seasons until conditions are right and they sprout. Yet once they start growing, such plants seem not to retain the ability to hit thebutton on metabolism in their stems or leaves.