光合作用
At the end of this lab, students should know...
什么是光合作用？
光合作用是将阳光转化为可利用和可储存能量的过程。自养生物（如植物）利用二氧化碳、水和从阳光中捕获的能量，通过光合作用生成葡萄糖和氧气，从而为食物网提供主要的能量来源。
植物如何利用太阳的能量？
植物会产生色素（如叶绿素），使其能够吸收太阳光中的能量。例如，光能会激发色素分子中的电子，这些能量随后被捕获并转化为简单糖类分子中的化学键。
植物细胞中负责光合作用的部分是什么？
叶绿体——其最内层膜结构中含有称为类囊体的色素——主要负责进行光合作用。
什么是碳封存？
在光合作用过程中，二氧化碳被用于生成简单的糖类。这些二氧化...
-
色谱柱联排管（18 X 3-4 cm 联排管）5
-
50 mL
-
管道清洁器5
-
塑料一次性注射器 （20 mL）10
-
回形针10
-
培培菜5
-
塑料/玻璃烧杯 （400 mL）15
-
打孔5
-
标尺5
-
永久标记5
-
铅笔5
-
Dawn 洗洁精 （1 瓶）1 每个站点
-
菠菜叶-1 取决于实验室大小
-
碳酸氢钠/小苏打-1 取决于实验室大小
- 植物色素色谱法与真空中的浮叶圆片
- 实验前一天，用一个容器装满水。
- 将菠菜叶片放入水中，并确保其完全浸没。
- 在室温下浸泡菠菜叶片过夜。
- 戴上手套，裁剪并量取尺寸为 18 cm × 304 cm 的色谱纸条。
- 为第二个实验配制碳酸氢盐溶液：将 0.25 g NaHCO₃ 与 300 mL 水混合，加入一滴洗洁精，轻轻搅拌混匀。
- 如果溶液仍有较多泡沫，可添加更多碳酸氢盐。
- 对照溶液的配制：将 300 mL 水与一滴洗洁精混合，轻轻搅拌，尽量避免产生泡沫。
- 在实验即将开始前，选取几片质地和厚度相近、大叶脉较少的菠菜叶片。
- 使用打孔器从叶片上制备每名学生或每个小组 20 片大小一致的圆片。
View the full transcript and gain access to JoVE Lab Manual videos
Q1: Why should spinach leaves soak overnight before a photosynthesis experiment?
Soaking spinach leaves overnight in water at room temperature hydrates the leaf tissue and prepares it for the experiment. This pre-treatment ensures uniform moisture content across all leaves, which is essential for consistent results when studying photosynthesis leaf disc experiment procedures and measuring pigment separation or gas exchange rates.
Q2: What is the purpose of adding dish soap to the bicarbonate solution?
Dish soap acts as a surfactant, reducing surface tension in the bicarbonate solution. This allows the solution to penetrate leaf tissue more effectively during vacuum infiltration, enabling better gas exchange and improving the experiment's ability to measure photosynthetic activity in the leaf discs.
Q3: How should chromatography paper be prepared for plant pigment separation?
Chromatography paper should be cut into uniform sections measuring 18 cm by 304 cm. Proper sizing ensures consistent results across all samples and allows adequate space for pigment separation during the chromatography process, making it easier to identify and compare different plant pigments.
Q4: Why is a control solution necessary in the floating leaf disc experiment?
A control solution containing only water and dish soap, without bicarbonate, provides a baseline for comparison. It allows researchers to isolate the effect of bicarbonate on leaf disc buoyancy and photosynthetic activity, ensuring that observed changes result from the bicarbonate treatment rather than other variables.
Q5: What criteria should be used when selecting spinach leaves for disc preparation?
Select spinach leaves with similar smoothness and thickness, avoiding those with large veins. Uniform leaf characteristics ensure that all discs have comparable surface area and tissue density, which reduces experimental variability and produces more reliable measurements of photosynthetic rates across the sample group.
Q6: How does the hole punch create uniform leaf discs for the experiment?
A hole punch cuts identical circular discs from prepared spinach leaves, typically producing 20 uniform discs per student or group. This standardization ensures each disc has the same surface area and mass, which is critical for accurate comparison of photosynthetic activity and gas exchange measurements between experimental conditions.
Q7: What is the relationship between bicarbonate concentration and photosynthetic activity in leaf discs?
Bicarbonate solution provides a source of dissolved carbon dioxide, which is essential for photosynthesis. The 0.25 g NaHCO3 per 300 mL water concentration supplies adequate CO2 to support photosynthetic reactions, allowing leaf discs to produce oxygen and float as a measurable indicator of photosynthetic performance.