PLANET EARTH Deserts

When the summer monsoon blows in the giant saguaros（巨人柱，仙人掌的一種）, one of the biggest of all cacti, are ready to take full advantage of it. After a rainstorm the saguaro's long shallow root system sucks up the water and the pleats（原意是褶皺，這里指的是仙人掌的根莖凹凸不平，粗糙不齊） on its trunk enable it to expand rapidly. When full, a saguaro stem can store up to five tons of water and that's enough to see it through many months of drought.



The trunks of these huge plants provide homes for the gila woodpecker（啄木鳥）. But birds are not the only animals to benefit from the presence of the cacti. During four weeks of the summer the saguaros bloom at night to attract visitors. The pollen（花粉） and nectar（花蜜） with which these flowers are loaded attract long-nosed and long-tongued bats. The bats left Mexico a few days earlier to escape the heat of summer and are on their way north to the southern United States.