Question

阅读理解 　　Today we tell you about some new understanding of why cutting the main branch of a plant or tree can lead to better development． 　　The findings are from researchers on two continents．Professor Prezemyslaw Prusinkiewicz of the University of Calgary in Canada led the research with scientists from Britain and Sweden．Their study appears in the Proceedings of the National Academy of Sciences． 　　Researchers have known since the 1930s that the actively growing tip of a plant produces a hormone(荷尔蒙)called auxin(生长素)．This hormone flows down the main stem．Scientists say the auxin has an indirect effect on buds(芽)on the side of the stem to prevent branching． 　　These buds themselves also produce auxin．The research suggests that to grow, they have to be able to export the hormone into the main stem．But the flow from the stem tip prevents them from doing this．The researchers wanted to find out how this blocking happens． 　　Professor Prusinkiewicz is on leave in Australia, but he sent us an e－mail suggesting a simple way to understand the process．Think of a major road crowded with traffic．So many cars are on the main road that the cars on the side roads cannot enter． 　　The stem is like the crowded main road．The new research shows that the buds on the side cannot export their auxin into the main stem because it is too full．But if that main shoot is pruned(修剪), other buds below it can start exporting．They are no longer prevented from growing． 　　Ottoline Leyser from the University of York says that after a plant is pruned, all the inhibited(被抑制的)shoot tips compete with each other to grow．In doing this, the branches influence each other’s growth．Nearby shoot tips are more likely to affect each other than those that are far apart from each other． 　　Professor Leyser says the strongest branches grow best, wherever they may be on the plant．The study found that the main shoot grows the best of all not because of its position at the top of the plant, but mostly because it got there first． (1) The underlined part “two continents” in Paragraph 2 refers to “________”． [　　] A． Asia and Africa B． Africa and Europe C． North America and Europe D． Australia and Europe (2) Professor Prusinkiewicz compares the cars on the side roads to ________． [　　] A． plant stems B． plant buds C． the leaves of a plant D． the roots of a plant (3) To make the buds on the side of the stem to grow better, the main shoot should ________． [　　] A． be cut off B． be protected C． be watered as much as possible D． be given much auxin (4) According to the passage, which of the following is TRUE? [　　] A． Researchers have recently found out that the growing tip of a plant produces hormones． B． Auxin has a direct effect on buds to keep branches from growing． C． Buds on the side of the stem can’t produce hormones． D． In order to grow, the buds on the side of the stem export the hormones into the main stem． (5) Which of the following may be the best title for this passage? [　　] A． Why shoot tips grow fast? B． When and how to prune plants? C． Scientists help cut the mystery behind pruning D． The great scientist－Prezemyslaw Prusinkiewicz

Answer 1

答案：1．C;2．B;3．A;4．D;5．C;
解析：

(1)	细节推理题。根据第二段提及的科学家的国籍可推测出，Canada属于北美，而Britain and Sweden属于欧洲。
(2)	细节理解题。根据文章第五、六段可知，Professor Prusinkiewicz把植物的芽比作马路支路上的汽车。
(3)	推理判断题。根据第六段But if that main shoot is pruned(修剪), other buds below it can start exporting．可知，为了让枝干上的芽生长，树顶的主芽应修剪掉。
(4)	细节理解题。根据第三段第一句话可知，科学家早在20世纪30年代就发现了植物快速生长的尖部产生荷尔蒙，A错误；由第三段第三句可知B错误；由第四段首句可知芽也可以产生生长素，C错误；D表述与第四段意思相符。
(5)	标题归纳题。文章第一段即点明了本文主旨。本文是对于修剪树木主干的新理解。