【雅思阅读分享篇】说说叶子那些事儿

做过剑桥真题10的同学会知道在雅思阅读test3中有篇文章讲树叶的事情，标题就是Autumn Leaves。里面有些貌似比较专业的词汇实际我们在中学的生物课上学植物相关内容的时候都有所涉猎，比如叶绿素(chlorophyl)、花青素(anthocyanin)、针叶树(conifer)等。此外很多同学觉得内容非常的专业，其实这是篇很平常的科普文章。

那么在雅思阅读中为什么这篇文章很多同学觉得内容难理解呢？一般会有以下几个原因：1.平时对科普文章涉猎太少，注意力被生词吸引，觉得高不可攀；2.相关的比较基本的背景知识不足，增加了理解的难度。

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如果你觉得雅思阅读中这些科普文章虐了你，那只能说明你还是被他们虐得不够。那么今天就让我们再挖一挖叶子的那些事吧。先让我们来看看什么是叶子，英文版哦~

A leaf is an organ of a vascular plant and is the principal lateral appendage of the stem. The leaves and stem together form the shoot. Foliage is a mass noun that refers to leaves collectively.
Typically a leaf is a thin, dorsiventrally flattened organ, borne above ground and specialized for photosynthesis. In most leaves, the primary photosynthetic tissue, the (palisade mesophyll), is located on the upper side of the blade or lamina of the leaf but in some species, including the mature foliage of Eucalyptus palisade mesophyll is present on both sides and the leaves are said to be isobilateral. Most leaves have distinctive upper (adaxial) and lower (abaxial) surfaces that differ in colour, hairiness, the number of stomata (pores that intake and output gases), epicuticular wax amount and structure and other features.

那叶子又是如何进化的呢？让我们来看看Leaf Adaptations： 【在线咨询】

Poinsettia bracts are leaves which have evolved red pigmentation in order to attract insects and birds to the central flowers, an adaptive function normally served by petals (which are themselves leaves highly modified by evolution).
In the course of evolution, leaves have adapted to different environments in the following ways:
·A certain surface structure avoids moistening by rain and contamination (See Lotus effect).
·Sliced leaves reduce wind resistance.
·Hairs on the leaf surface trap humidity in dry climates and create a boundary layer reducing water loss.
·Waxy leaf surfaces reduce water loss.
·Large surface area provides large area for sunlight and shade for plant to minimize heating and reduce water loss.
·In harmful levels of sunlight, specialised leaves, opaque or partly buried, admit light through a translucent leaf window for photosynthesis at inner leaf surfaces (e.g. Fenestraria).
·Succulent leaves store water and organic acids for use in CAM photosynthesis.
·Aromatic oils, poisons or pheromones produced by leaf borne glands deter herbivores (e.g. eucalypts).
·Inclusions of crystalline minerals deter herbivores (e.g. silica phytoliths in grasses, raphides in Araceae).
·Petals attract pollinators.
·Spines protect the plants (e.g. cacti).
·Special leaves on carnivorous plants are adapted to trapping food, mainly invertebrate prey, though some species trap small vertebrates as well (see carnivorous plants).
·Bulbs store food and water (e.g. onions).
·Tendrils allow the plant to climb (e.g. peas).
·Bracts and pseudanthia (false flowers) replace normal flower structures when the true flowers are greatly reduced (e.g. Spurges).
·Spathe.

雅思阅读高分词汇Vocabulary:  【在线咨询更多词汇】

apex （n.）叶子的尖端
midvein (Primary vein) （n.）中脉
secondary vein （n.）副脉
lamina （n.） 叶片
leaf margin（n.） 叶缘
petiole（n.） 叶柄
bud（n.）芽
stem（n.）茎
palisade（n.）细胞层
mesophyll（n.）叶肉
isobilateral（adj.）等面的
stomata（n.）气孔
epicuticular wax（n.）表面蜡质
poinsettia bract   n. 一品红苞片
fenestraria  n.棒叶花属
succulent  adj. 多汁的；多水分的；多汁性的, n. 肉质植物；多汁植物
photosynthesis n. 光合作用
aromatic adj. 芳香的，芬芳的；芳香族的 ,n. 芳香植物；芳香剂
pheromone n. 信息素（用于生化领域）；费洛蒙（昆虫分泌以刺激同种昆虫之化合物质）
herbivores n. [动] 食草动物，植食动物；食草者（herbivore的复数形式）
crystalline adj. 透明的；水晶般的；水晶制的
petal n. 花瓣
carnivorous adj. 食肉的；肉食性的
tendrils n. [植] 卷须；卷须状物（tendril的复数形式）
pseudanthia n. [植] 伪花（pseudanthium的复数形式）
spathe n. [植] 佛焰苞

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