📚 GCSE WJEC Science: Plants – Key Points | GCSE WJEC 科学：植物 考点精讲
Welcome to your focused revision guide for the plant topics in GCSE WJEC Science. A thorough understanding of plant biology can make a real difference in your exam performance. This resource unpacks essential ideas – from cellular structures and photosynthesis to transport systems, hormones, and reproduction – with clear paired explanations in English and Chinese so you can reinforce your learning efficiently.
欢迎使用这本针对 GCSE WJEC 科学植物考点的精讲指南。深入理解植物生物学能有效提高你的考试成绩。本资料逐项讲解核心概念——从细胞结构和光合作用到运输系统、激素和繁殖——并用英中双语对照讲解，帮助你高效巩固知识。
1. Plant Cells and Tissues | 植物细胞和组织
Plant cells have a strong cell wall made of cellulose. This gives each cell a fixed shape and provides structural support for the whole plant.
植物细胞有由纤维素组成的坚固细胞壁。它使每个细胞具有固定的形状，并为整个植物提供结构支持。
A large, permanent vacuole filled with cell sap helps maintain turgor pressure. When the vacuole is full, the cytoplasm presses against the cell wall, keeping the plant upright.
一个充满细胞液的大中央液泡有助于维持膨压。当液泡充满时，细胞质紧贴细胞壁，使植物保持直立。
Chloroplasts are the organelles where photosynthesis occurs. They contain the green pigment chlorophyll, which absorbs light energy to drive the reaction.
叶绿体是进行光合作用的细胞器。它们含有绿色色素叶绿素，叶绿素吸收光能来驱动反应。
In leaves, the main tissues include the upper epidermis for protection, palisade mesophyll packed with chloroplasts for photosynthesis, and spongy mesophyll with air spaces for gas exchange. Vascular bundles containing xylem and phloem run through the leaf for transport.
叶片的主要组织包括起保护作用的上表皮、富含叶绿体的栅栏组织（进行光合作用）以及具有气室的海绵组织（用于气体交换）。包含木质部和韧皮部的维管束贯穿叶片，负责运输。
2. Photosynthesis Equation and Products | 光合作用方程式和产物
Photosynthesis is an endothermic reaction that uses light energy to convert carbon dioxide and water into glucose and oxygen. Chlorophyll in the chloroplasts acts as a catalyst.
光合作用是吸热反应，利用光能将二氧化碳和水转化为葡萄糖和氧气。叶绿体中的叶绿素起催化作用。
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
The glucose produced can be used immediately in respiration to release energy. It is also converted into starch for storage, cellulose to build cell walls, or combined with nitrate ions to make amino acids and proteins.
产生的葡萄糖可以立即在呼吸作用中释放能量，也可以转化为淀粉储存，转化为纤维素构建细胞壁，或者与硝酸根离子结合生成氨基酸和蛋白质。
Oxygen is released as a by‑product and exits the leaf through the stomata. Some of it is used by the plant for respiration, but much diffuses into the atmosphere.
氧气作为副产品释放，通过气孔离开叶片。部分氧气被植物用于呼吸，但大部分扩散到大气中。
3. Limiting Factors of Photosynthesis | 光合作用的限制因素
The rate of photosynthesis is affected by light intensity, carbon dioxide concentration, and temperature. A limiting factor is the factor in shortest supply that restricts the rate.
光合作用速率受光照强度、二氧化碳浓度和温度的影响。限制因素是指供应最不足、从而制约反应速率的因素。
As light intensity increases, the rate rises until another factor becomes limiting. On a graph, the curve flattens when light is no longer the limiting factor – perhaps CO₂ concentration or temperature is now restricting the rate.
随着光照强度增加，光合速率上升，直到另一个因素成为限制因素。在图表中，当光照不再是限制因素时曲线趋于平缓——可能是二氧化碳浓度或温度限制了速率。
At low CO₂ levels, the rate is low even if light is abundant. Similarly, if the temperature is too low, enzyme activity slows down; if it is too high, enzymes denature and the rate drops sharply.
在低二氧化碳浓度下，即使光照充足速率也很低。同样，温度过低时酶活性降低；温度过高时酶变性，速率急剧下降。
Gardeners and farmers use this knowledge to boost crop growth. In greenhouses, they add extra lighting, enrich the air with CO₂, and maintain an optimal temperature to maximise photosynthesis.
园艺人员和农民运用这些知识促进作物生长。在温室中，他们增加补光灯、补充二氧化碳并保持最适温度，以最大限度地提高光合作用。
4. Structure of a Leaf | 叶的结构
A leaf is a plant organ whose structure is perfectly adapted for photosynthesis and gas exchange. The top surface is covered by a waxy cuticle that reduces water loss.
叶片是适合光合作用和气体交换的植物器官。上表面覆盖着蜡质角质层，以减少水分流失。
The upper epidermis is a single layer of transparent cells that allows light to pass through to the palisade mesophyll below. Palisade cells are tall, packed with chloroplasts, and arranged close together to capture as much light as possible.
上表皮是一层透明的细胞，让光线透过到达下方的栅栏组织。栅栏细胞细长，富含叶绿体，排列紧密，以捕获尽可能多的光能。
Beneath the palisade layer, the spongy mesophyll has large air spaces that allow carbon dioxide to diffuse in and oxygen to diffuse out. This loose arrangement also provides a large surface area for gas exchange.
在栅栏层下方，海绵组织具有大的气腔，允许二氧化碳扩散进入，氧气扩散出去。这种松散的结构也为气体交换提供了大表面积。
The lower epidermis contains many stomata – tiny pores surrounded by guard cells. Guard cells change shape to open or close the stomata, controlling the movement of gases and water vapour.
下表皮含有许多气孔——由保卫细胞包围的微小开口。保卫细胞通过改变形状来打开或关闭气孔，控制气体和水蒸气的进出。
5. Xylem and Phloem | 木质部和韧皮部
Xylem tissue transports water and dissolved mineral ions from the roots up to the stems and leaves. Xylem vessels are dead, hollow cells with thick, lignin‑reinforced walls that provide strength and prevent collapse.
木质部组织将水和溶解的矿物质离子从根部向上运输到茎和叶。木质部导管是死去的空心细胞，具有由木质素加厚的壁，既提供强度又防止塌陷。
Water movement in the xylem is always unidirectional – from roots to shoots. The lignin in the walls may form rings or spirals, which can be seen clearly in a longitudinal section of stem tissue.
水分在木质部中的运输始终是单向的——从根部到地上部分。壁中的木质素可形成环形或螺旋状增厚，在茎的纵剖面上清晰可见。
Phloem tissue transports dissolved organic substances, mainly sucrose and amino acids, from sources (where they are made or released) to sinks (where they are used or stored). Unlike xylem, phloem is made of living cells.
韧皮部组织运输溶解的有机物，主要是蔗糖和氨基酸，从“源”（产生或释放这些物质的地方）运往“库”（使用或储存这些物质的地方）。与木质部不同，韧皮部由活细胞构成。
Phloem consists of sieve tube elements, which have end‑plates with pores to allow sap flow, and companion cells that provide energy for active transport. Transport in phloem can be bidirectional, moving up or down depending on where the sugars are needed.
韧皮部由筛管分子和伴胞组成；筛管分子端壁上有筛孔允许汁液流动，伴胞为主动运输提供能量。韧皮部中的运输可以是双向的，根据需求向上或向下移动。
6. Transpiration Stream | 蒸腾流
Transpiration is the loss of water vapour from the aerial parts of a plant, mainly through stomata. It creates a suction force that pulls water up through the xylem in a continuous column – this is called the transpiration stream.
蒸腾作用是植物地上部分（主要是通过气孔）散失水蒸气的过程。它产生一股吸力，使水分以连续水柱的形式通过木质部向上运输——这就是蒸腾流。
Water molecules stick to each other (cohesion) and to the walls of the xylem (adhesion). These forces, together with the narrow diameter of xylem vessels, allow the water column to be pulled up without breaking.
水分子之间存在内聚力，同时水分子与木质部管壁之间存在附着力。这些力加上木质部导管的细小直径，使得水柱在被向上拉拽时不会断裂。
Several environmental factors affect the rate of transpiration: higher temperature and wind speed increase the rate, while high humidity decreases it. Brighter light usually causes stomata to open wider, speeding up water loss.
多种环境因素影响蒸腾速率：较高的温度和风速会加快蒸腾，高湿度则减慢蒸腾。强光通常使气孔开得更大，从而加快水分流失。
You can measure the rate of water uptake using a potometer. A bubble or a moving meniscus indicates how quickly the plant takes up water, which is an estimate of transpiration rate under controlled conditions.
你可以用蒸腾计测量水分吸收速率。气泡或移动的半月面显示植物吸收水分的速度，这是在受控条件下对蒸腾速率的估算。
7. Translocation | 输导作用
Translocation is the movement of dissolved sugars (especially sucrose) and amino acids through the phloem. It is an active process that requires energy from respiration.
输导作用是溶解的糖类（特别是蔗糖）和氨基酸通过韧皮部的运输过程。这是一个需要呼吸作用提供能量的主动过程。
The ‘source’ is a region where sugars are produced or released, such as a mature leaf carrying out photosynthesis. The ‘sink’ is where they are used for growth, respiration or storage – for example, growing root tips or developing fruits.
“源”是产生或释放糖的区域，例如进行光合作用的成熟叶片。“库”则是糖类被用于生长、呼吸或储存的区域，例如正在生长的根尖或发育中的果实。
Phloem transport is driven by differences in solute concentration. Sugars are actively loaded into the phloem at the source, lowering the water potential and causing water to enter by osmosis. This builds up pressure, pushing the sap towards the sink.
韧皮部运输由溶质浓度差驱动。在源端，糖被主动装载到韧皮部，降低水势，使水分通过渗透进入。这增加了压力，将汁液推向库端。
8. Mineral Requirements and Deficiency | 矿质需求与缺乏症
Plants need mineral ions absorbed from the soil through their roots. Two of the most important are nitrate ions (NO₃⁻) for building proteins and magnesium ions (Mg²⁺) for making chlorophyll.
植物需要通过根部从土壤中吸收矿质离子。其中最重要的两种是用于合成蛋白质的硝酸根离子（NO₃⁻）和用于制造叶绿素的镁离子（Mg²⁺）。
Without enough nitrate, a plant cannot produce sufficient protein for growth. The typical symptom is stunted growth and yellowing of older leaves, as nitrogen is mobile and gets transported to younger parts.
缺少足够的硝酸盐，植物无法产生足够的蛋白质用于生长。典型症状是生长受阻和老叶黄化，因为氮是可移动元素，会被转运到较幼嫩的部分。
A shortage of magnesium ions prevents the formation of chlorophyll, causing chlorosis – the leaves turn yellow, especially between the veins. Photosynthesis is reduced, and the plant becomes weak.
镁离子不足会阻碍叶绿素的形成，导致失绿症——叶片变黄，尤其是叶脉之间。光合作用减弱，植株变得虚弱。
Other essential minerals include phosphate for ATP and cell membranes, and potassium for stomatal opening and enzyme activation. Deficiency symptoms can help gardeners diagnose which minerals are lacking.
其他必需矿质包括用于合成ATP和细胞膜的磷酸盐，以及用于气孔开闭和酶活化的钾。缺乏症状可以帮助园丁判断缺少哪种矿质元素。
9. Plant Hormones: Auxin | 植物激素：生长素
Plant hormones are chemical messengers that coordinate growth and responses. Auxin is a key hormone produced in the tips of shoots and roots, and it controls cell elongation.
植物激素是协调生长和响应的化学信使。生长素是一种关键激素，在茎尖和根尖产生，控制着细胞的伸长。
When light shines on one side of a shoot tip, auxin redistributes towards the shaded side. The higher concentration of auxin there stimulates cells to elongate more than on the illuminated side, causing the shoot to bend towards the light.
当光线照射在芽尖的一侧时，生长素重新分布到背光侧。背光侧较高的生长素浓度刺激细胞比向光侧伸长得更快，导致茎尖向光弯曲。
In roots, a high concentration of auxin inhibits cell elongation. This is why roots grow away from light (negative phototropism) and respond strongly to gravity.
在根部，高浓度的生长素会抑制细胞伸长。这就是为什么根背光生长（负向光性），并且对重力有强烈反应。
Classic experiments with oat coleoptiles showed that if the tip is removed, growth stops; if the tip is covered with an opaque cap, no bending occurs; but if the tip is covered with a transparent cap, bending still happens. Removing the tip can be reversed by replacing it or by putting a block of agar that has absorbed auxin on the cut surface.
经典的燕麦胚芽鞘实验表明：摘除尖端生长停止；用不透光帽盖住尖端不发生弯曲；但用透明帽盖住尖端仍会弯曲。摘除尖端后，如果将其放回原处或用吸收了生长素的琼脂块放在切口上，可以恢复生长。
10. Tropisms: Phototropism and Gravitropism | 向性：向光性和向地性
Tropisms are directional growth responses in which a plant part grows towards or away from a stimulus. Phototropism is a response to light, and gravitropism (also called geotropism) is a response to gravity.
向性是指植物器官朝着或背离某个刺激方向生长的响应。向光性是对光的响应，向地性（也称向重力性）是对重力的响应。
Shoots show positive phototropism – they grow towards light. This maximises light capture for photosynthesis. Roots are negatively phototropic, helping them stay underground searching for water.
茎表现为正向光性，即向光生长。这可以最大限度地捕获光能用于光合作用。根表现为负向光性，帮助它们留在土壤中寻找水分。
In gravitropism, roots grow downwards (positive gravitropism) and shoots grow upwards (negative gravitropism). Auxin plays a central role: in a horizontally placed root, more auxin accumulates on the lower side, where it inhibits growth, causing the root to bend downwards.
在向地性中，根向下生长（正向地性），茎向上生长（负向地性）。生长素发挥核心作用：在水平放置的根中，更多的生长素积聚在下侧，抑制该侧的生长，导致根向下弯曲。
Understanding tropisms helps explain how plants survive. For example, a germinating seed buried in soil will send a shoot upwards towards light and a root downwards towards moisture, regardless of how the seed is oriented.
理解向性有助于解释植物的生存机制。例如，即使种子在土壤中方向随意，萌发后仍会向上伸出芽寻找光，向下扎根寻找水分。
11. Sexual Reproduction in Flowering Plants | 有花植物的有性生殖
Most flowering plants reproduce sexually, producing seeds that grow into new individuals. The flower is the sexual organ, containing male stamens (anther + filament) and female carpels (stigma, style, ovary).
大多数有花植物进行有性生殖，产生种子长成新个体。花是生殖器官，包含雄性雄蕊（花药和花丝）和雌性心皮（柱头、花柱、子房）。
Pollination is the transfer of pollen from an anther to a stigma. Insect‑pollinated flowers tend to be brightly coloured, scented and have sticky pollen. Wind‑pollinated flowers are usually small, dull and produce huge amounts of light, smooth pollen.
传粉是将花粉从花药转移到柱头的过程。虫媒花通常颜色鲜艳、有香气、花粉有黏性。风媒花通常较小、不鲜艳，产生大量轻而光滑的花粉。
After pollination, a pollen tube grows down the style into the ovary, delivering male nuclei to the ovule. Fertilisation occurs when a male nucleus fuses with the egg cell, forming a zygote. The ovule then develops into a seed, and the surrounding ovary develops into a fruit.
传粉后，花粉管沿花柱向下生长进入子房，将雄核送入胚珠。一个雄核与卵细胞融合形成受精卵，完成受精。随后胚珠发育成种子，包裹它的子房发育成果实。
Cross‑pollination increases genetic variation, giving populations a better chance of surviving environmental change. Devices such as staggered stamen and stigma maturity or self‑incompatibility help plants avoid self‑pollination.
异花传粉增加遗传变异，使种群更有机会在环境变化中存活。一些机制如雌雄蕊不同时成熟或自交不亲和能够帮助植物避免自花传粉。
12. Germination and Investigations | 萌发与实验探究
Germination is the process by which a seed develops into a new plant. The three key conditions required are water, oxygen and a suitable temperature (warmth).
萌发是种子发育成新植株的过程。必需的三个关键条件是：水、氧气和适宜的温度（温暖）。
Published by TutorHao | GCSE Science Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图