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neurologyYou need to know

• Plants require light, carbon dioxide, water, and mineral ions to survive and grow.
• The word equation for photosynthesis is `\text{carbon dioxide} + \text{water} \rightarrow \text{glucose} + \text{oxygen}` in the presence of light and chlorophyll.
• The balanced chemical equation for photosynthesis is `6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2`.
• Photosynthesis occurs in chloroplasts, where chlorophyll absorbs the light energy used in the process.
• During photosynthesis, light energy is converted into chemical energy stored in glucose.
• The main structures of a leaf include the cuticle, upper epidermis, palisade mesophyll, spongy mesophyll, vascular bundles (xylem and phloem), lower epidermis, and stomata.
• Leaves are adapted for photosynthesis by having a large surface area, a thin structure, chloroplasts concentrated in the palisade layer, stomata for gas exchange, and veins for water and nutrient transport.
• Starch is a storage form of glucose in plants and can be tested for using iodine solution.
• Glucose produced in photosynthesis can be used for respiration, converted into starch for storage, and used to make cellulose for cell walls.
• The three main limiting factors of photosynthesis are light intensity, carbon dioxide concentration, and temperature.
• Each limiting factor can restrict the rate of photosynthesis if it is in short supply.
• Increasing light intensity, carbon dioxide concentration, or temperature up to an optimum increases the rate of photosynthesis, but only until another factor becomes limiting.
• Farmers can manipulate limiting factors, such as using greenhouses, artificial lighting, carbon dioxide enrichment, and temperature control, to increase crop yields.

• Test a leaf for starch by first boiling it in water, then heating it in ethanol using a hot-water bath with all naked flames extinguished because ethanol is highly flammable, rinsing it in warm water, and adding iodine solution to observe a colour change.
• Describe and explain how the structure of a leaf is adapted for efficient photosynthesis.
• Sketch and interpret graphs showing the effect of light intensity, carbon dioxide concentration, and temperature on the rate of photosynthesis.
• Measure the rate of photosynthesis, for example by counting the number of oxygen bubbles produced by pondweed in a set time or using a gas syringe.
• Plot a graph of the rate of photosynthesis against increasing light intensity and interpret the results.
• Apply knowledge of limiting factors to explain how farmers can increase crop yields by controlling environmental conditions.