Section II Reading Comprehension
Part A
Directions: Read the following four texts. Answer the questions below each text by choosing A, B, C or D. Mark your answers on the ANSWER SHEET.
Text 1
Not all deciduous trees shed their leaves before winter. In forests across North America, Europe and parts of Asia, many oak and beech trees retain their dry brown leaves until spring. The phenomenon, known as leaf marcescence, has been recorded for centuries, yet scientists still cannot fully explain why certain plants fail to release leaves that no longer contribute to growth.
Under normal circumstances, deciduous trees prepare for winter by withdrawing nutrients from their leaves and transporting them back into the trunk and roots. They then develop a thin layer of cells at the base of each leaf, allowing it to separate naturally from the branch. In marcescent trees, however, this process remains incomplete. Although the leaves die, they stay attached throughout the cold season and are not shed until new growth begins in spring.
The puzzle attracted Mason Heberling, a botanist at the Carnegie Museum of Natural History, while he was studying seasonal changes in forests. During field observations, he noticed that many young beech trees retained dead leaves, particularly on their lower branches, making it difficult to determine precisely when leaf fall had occurred. What first appeared to be an inconvenience in collecting data gradually became a scientific question in its own right.
To find out how common the phenomenon really is, researchers surveyed more than 1,000 plant species in botanical gardens across North America, Europe and Asia during the winters of 2024 and 2025. Their results challenged long-held assumptions. More than 400 species retained at least some dead leaves, while over 150 species kept a quarter or more of their foliage intact. The survey also revealed that marcescence occurred more frequently in colder climates and was especially noticeable among younger trees and on lower branches.
The findings suggest that leaf marcescence may represent an inherited characteristic rather than an accidental failure of leaf development. Some groups, particularly oaks, display the trait much more often than others, indicating that genetics probably plays an important role. Yet the picture is far from straightforward. Even closely related trees may differ considerably, suggesting that environmental conditions also influence whether leaves remain attached. Researchers have identified regions of the genome associated with the trait, but no individual gene has yet been confirmed as responsible.
If the behavior is inherited, why has it survived through evolution? Scientists have proposed several explanations. One widely discussed hypothesis is that dead leaves discourage animals such as deer from feeding on nutritious buds during winter. The dry leaves are relatively unpalatable and may also conceal the buds, making them less attractive to hungry herbivores. Another possibility is that the retained leaves provide physical protection against frost or strong winter winds.
Other researchers focus on what happens after the leaves finally fall. Leaves that remain exposed to sunlight throughout winter become thinner and begin to break down before reaching the ground. As a result, they may decompose more rapidly in spring, returning nutrients to the soil sooner than leaves that fell in autumn. Such a process could provide an advantage at the beginning of the growing season, when trees require nutrients most urgently.
Despite these hypotheses, scientists caution that no single explanation has received decisive support. It is even possible that leaf marcescence has little adaptive value and simply persists because it does not reduce a tree's chances of surviving or reproducing. Rather than offering a final answer, current research highlights how much remains unknown about even the most familiar features of the natural world.
21. What first led Heberling to investigate leaf marcescence?
[A] Historical descriptions of unusual winter forests.
[B] A problem encountered during his field research.
[C] A newly published study on plant genetics.
[D] Public interest in seasonal changes.
22. What did the international survey mainly reveal about leaf marcescence?
[A] It is largely confined to oak and beech trees.
[B] It occurs much more widely than previously assumed.
[C] It is becoming increasingly common because of climate change.
[D] It appears only in young trees living in cold regions.
23. According to the passage, what can be inferred about the genetic basis of leaf marcescence?
[A] Scientists have already identified the exact gene responsible.
[B] Genetic factors alone are sufficient to explain the phenomenon.
[C] The trait is likely inherited, but other influences are also involved.
[D] Environmental conditions are more important than heredity.
24. Why does the author mention the decomposition of retained leaves?
[A] To support one possible explanation for the persistence of marcescence.
[B] To demonstrate that dead leaves contain more nutrients than living ones.
[C] To show that sunlight prevents leaves from decomposing.
[D] To explain why deciduous trees lose leaves in autumn.
25. Which of the following best summarizes the passage?
[A] Scientists have finally solved the mystery of leaf marcescence.
[B] Leaf marcescence is an evolutionary error that should disappear over time.
[C] Ongoing research suggests several explanations for leaf marcescence, but none has been confirmed.
[D] Environmental change has fundamentally altered the leaf-fall patterns of deciduous trees.
附注：根据历年考研英语真题阅读题源外刊等，摘选最新文章，模拟仿真出题。
参考答案见以下。
Quick look: BBCAC
21.【正确答案】B
【解析】题型：细节理解题（事实定位）
定位：第三段第二、三句
"During field observations, he noticed that many young beech trees retained dead leaves... making it difficult to determine precisely when leaf fall had occurred."
分析：
Heberling原本研究的是森林季节变化（seasonal changes），而年轻山毛榉保留枯叶导致其难以准确记录落叶时间。这一研究过程中遇到的问题，引发了他对叶片滞留现象的兴趣。因此B项 A problem encountered during his field research 是对原文的准确概括。
干扰项：
[A] 文中提到历史记录只是介绍背景，并非其研究起点。
[C] 基因研究属于后续研究成果，不是研究动机。
[D] 原文没有提及公众兴趣，属于无中生有。
22.【正确答案】B
【解析】题型：细节理解题（研究发现）
定位：第四段第三、四句
"Their results challenged long-held assumptions. More than 400 species retained at least some dead leaves..."
分析：
调查最大的发现并不是发现了新的树种，而是证明叶片滞留远比过去认为的更加普遍，因此B项 It occurs much more widely than previously assumed. 是对 challenged long-held assumptions 的同义替换。
干扰项：
[A] 原文明确指出超过400种植物存在该现象，并非仅限橡树和山毛榉。
[C] 文章没有说明由于气候变化导致越来越普遍。
[D] 原文只是说年轻树木更加明显，而不是只有年轻树木才存在。
23.【正确答案】C
【解析】题型：推理判断题（观点理解）
定位：第五段
"genetics probably plays an important role... Even closely related trees may differ considerably, suggesting that environmental conditions also influence..."
分析：
文章认为遗传因素具有重要作用，但同时指出环境条件同样可能影响叶片是否保留，因此作者并未认为遗传能够完全解释该现象。C项 The trait is likely inherited, but other influences are also involved. 最符合作者观点。
干扰项：
[A] 原文明确说尚未确认具体基因（no individual gene has yet been confirmed）。
[B] "alone"属于绝对化表达，与原文相反。
[D] 作者没有比较遗传与环境谁更重要，只强调二者共同作用。
24.【正确答案】A
【解析】题型：写作目的题（举例作用）
定位：第七段
"As a result, they may decompose more rapidly in spring, returning nutrients to the soil sooner..."
分析：
作者介绍叶片更快分解，并不是介绍分解过程本身，而是为了说明一种关于叶片滞留进化意义的假说，即叶片延迟掉落能够帮助养分快速回归土壤。因此A项准确概括了举例目的。
干扰项：
[B] 原文没有比较死叶和活叶营养含量。
[C] 原文恰恰说阳光促进分解。
[D] 与秋季落叶机制无关，属于偷换论题。
25.【正确答案】C
【解析】题型：主旨大意题（全文主旨）
定位：最后一段
"Despite these hypotheses... no single explanation has received decisive support."
分析：
全文围绕"为什么树木会保留枯叶"展开，介绍多个研究成果和不同假说，最后指出目前尚无任何一种解释得到决定性证据支持。因此C项最能概括全文中心。
干扰项：
[A] 与文章结论相反。
[B] 文中没有认为这是进化错误。
[D] 气候变化只是调查结果中的一个相关因素，并非全文主题。
【词汇注释】
deciduous: adjective (PLANTS) trees that lose their leaves every year 落叶的
marcescence: noun the retention of dead leaves that normally fall naturally 枯叶滞留现象
shed: verb (LEAVES) to lose leaves naturally （树木）落叶
withdraw: verb remove or take back 收回；回收（养分）
transport: verb move from one place to another 输送；运输
retain: verb continue to keep 保留；保持
foliage: noun the leaves of a plant 树叶；叶簇
inherit: verb receive genetically 遗传
trait: noun a particular characteristic 特征；性状
genome: noun the complete set of genes 基因组
herbivore: noun an animal that eats plants 食草动物
decompose: verb break down naturally 分解；腐烂
nutrient: noun a substance that provides nourishment 营养物质
adaptive: adjective helping survival 适应性的
reproduce: verb produce offspring 繁殖；繁衍
hypothesis: noun a suggested explanation that has not yet been proved 假说
decisive: adjective providing a definite answer 决定性的；确定性的
persist: verb continue to exist 持续存在
assumption: noun something accepted as true without proof 假设；固有看法
botanist: noun a scientist who studies plants 植物学家
【长难句】
Even closely related trees may differ considerably, suggesting that environmental conditions also influence whether leaves remain attached.
句子主干是 Even closely related trees may differ considerably（即使亲缘关系非常接近的树木，其表现也可能存在明显差异）; suggesting 为现在分词作结果状语，表示"这一现象说明……"; that 引导宾语从句，作 suggesting 的宾语; 宾语从句中，whether 引导宾语从句，作 influence 的宾语，表示"叶片是否继续保留"。
即使亲缘关系十分接近的树木，其表现仍可能存在明显差异，这说明环境因素也可能影响叶片是否继续保留在树枝上。
【参考译文】
并非所有落叶树都会在冬天到来之前落叶。在北美、欧洲以及亚洲部分地区的森林中，许多橡树和山毛榉会一直保留干枯的褐色叶片直到春季。这种现象被称为枯叶滞留（leaf marcescence）。尽管数百年来一直有人记录这一现象，科学家至今仍无法完全解释为什么某些植物没有脱落那些已经不再促进生长的叶片。
正常情况下，落叶树会在冬季来临之前回收叶片中的养分，并将其输送回树干和根部。随后，叶柄基部会形成一层特殊细胞，使叶片自然脱落。然而，在发生枯叶滞留的树木中，这一过程并未完全完成。叶片虽然已经死亡，却会一直附着在树枝上，直到春季新叶萌发时才脱落。
卡内基自然历史博物馆植物学家梅森·赫伯林在研究森林季节变化时注意到了这一现象。在野外调查过程中，他发现许多年轻山毛榉，尤其是下部枝条，仍然保留着枯叶，这使得他难以准确判断树木真正的落叶时间。最初只是数据收集中的一个小问题，后来逐渐发展成为一个值得深入研究的科学问题。
为了弄清这一现象究竟有多普遍，研究人员于2024年至2025年冬季调查了北美、欧洲和亚洲植物园中的1000多种植物。调查结果推翻了长期以来的认识。超过400种植物至少保留了一部分枯叶，150多种植物甚至保留了四分之一以上的叶片。研究还发现，寒冷地区更容易出现枯叶滞留，而年轻树木及其下部枝条表现得尤为明显。
这些发现表明，枯叶滞留可能是一种遗传性状，而不是叶片发育失败造成的偶然现象。一些植物类群，尤其是橡树，比其他植物更常表现出这一特征，这说明遗传因素可能发挥着重要作用。然而，情况远没有如此简单。即使是亲缘关系十分接近的树木，其表现也可能存在明显差异，这说明环境条件同样会影响叶片是否继续附着。研究人员已经发现了与该性状相关的部分基因组区域，但至今尚未确认具体负责这一现象的基因。
如果这种行为确实能够遗传，那么它为何能够在进化过程中保留下来？科学家提出了几种解释。其中较为流行的一种观点认为，枯叶能够阻止鹿等食草动物啃食富含营养的新芽。干枯叶片不仅缺乏适口性，还可能遮挡嫩芽，使其不易被发现。另一种解释认为，保留下来的叶片能够帮助嫩芽抵御霜冻和冬季强风。
还有一些研究者关注叶片最终脱落之后发生的变化。由于整个冬季暴露在阳光下，这些叶片会逐渐变薄，并在落地之前开始分解。因此，当它们最终落到地面时，会比秋季脱落的叶片更快分解，使养分更早回归土壤。这一过程可能使树木在春季重新生长、最需要养分的时候获得一定优势。
尽管存在上述各种假说，科学家仍然强调，目前没有任何一种解释得到决定性的证据支持。甚至还有一种可能，即枯叶滞留本身几乎没有适应价值，只是因为它不会降低树木生存和繁殖的能力，因此一直保留至今。当前的研究并没有给出最终答案，而是再次提醒我们：即便是自然界中最常见的现象，仍然存在许多尚未解开的谜团。