📚 Photosynthesis and Plant Transport | 光合作用与植物运输
Photosynthesis is the biochemical process through which green plants use light energy to convert carbon dioxide and water into glucose and oxygen. The products of photosynthesis are essential food for plants and the ultimate source of biomass for most ecosystems.
光合作用是绿色植物利用光能将二氧化碳和水转化为葡萄糖和氧气的生化过程。光合作用产生的物质是植物的重要养分，也是大多数生态系统中生物量的最终来源。
1. The Photosynthesis Equation | 光合作用方程式
The overall equation for photosynthesis can be written in words and symbols. In IGCSE science, you must be able to balance the equation and identify the raw materials and products.
光合作用的总方程式可以用文字和符号书写。在IGCSE科学中，你必须能够配平方程式并识别原料和产物。
Carbon dioxide + Water → Glucose + Oxygen
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
The reaction is endothermic, meaning that energy from sunlight is transferred to the chemical bonds of glucose. The oxygen released as a by-product comes from the splitting of water molecules, not from carbon dioxide.
该反应是吸热反应，意味着来自阳光的能量被转移至葡萄糖的化学键中。作为副产物释放的氧气来自水分子的分解，而不是来自二氧化碳。
2. Leaf Structure and Adaptations | 叶片结构与适应性
Leaves are highly specialised organs for photosynthesis. Their flat and broad shape maximises the surface area for absorbing light. The internal structure includes several layers of tissues with specific functions.
叶片是高度特化的光合作用器官。其扁平宽阔的形状最大化了吸收光能的表面积。内部结构包括数层具有特定功能的组织。
- Epidermis: a transparent outer layer that lets light pass through and reduces water loss. | 表皮：透明的外层，允许光线透过并减少水分流失。
- Palisade mesophyll: closely packed cells with many chloroplasts, located near the upper surface. | 栅栏组织：含有大量叶绿体的紧密排列细胞，位于近上表面。
- Spongy mesophyll: loosely packed cells with air spaces to allow gas exchange. | 海绵组织：细胞排列疏松，具有气室以进行气体交换。
- Stomata: tiny pores, mostly on the lower epidermis, that control gas exchange and water loss. | 气孔：大多数位于下表皮的小孔，控制气体交换和水分流失。
Chloroplasts contain the green pigment chlorophyll, which absorbs light energy mainly in the red and blue regions of the spectrum. Each chloroplast is surrounded by a double membrane and contains stacks of thylakoids called grana.
叶绿体含有绿色色素叶绿素，主要吸收光谱中红光和蓝光区域的光能。每个叶绿体由双层膜包围，内部含有由类囊体堆叠而成的基粒。
3. Factors Affecting Photosynthesis | 影响光合作用的因素
The rate of photosynthesis is limited by several external and internal factors. According to the law of limiting factors, the rate is limited by the factor that is in shortest supply.
光合作用的速率受多种外部和内部因素限制。根据限制因子定律，速率受供应最少因素的制约。
