Nutrition in Flowering Plants – Photosynthesis (Chapter 12 Part 1)

Vocabulary flashcards covering key terms, structures, processes, and experimental concepts related to photosynthesis in flowering plants.

Photosynthesis

Process in which light energy absorbed by chlorophyll is converted to chemical energy, producing glucose from carbon dioxide and water and releasing oxygen as a by-product.

Chlorophyll

Green pigment in chloroplasts that absorbs light energy and initiates the reactions of photosynthesis.

Photosynthesis – Word Equation

Carbon dioxide + water ⟶ glucose + oxygen (in the presence of light and chlorophyll).

Photosynthesis – Chemical Equation

6 CO₂ + 6 H₂O ⟶ C₆H₁₂O₆ + 6 O₂ (light, chlorophyll).

Limiting Factor (photosynthesis)

Any variable that directly influences the rate of photosynthesis when in short supply (e.g., light intensity, CO₂ concentration, temperature, pH, water).

Light Intensity (as a limiting factor)

Amount of light available; below point X it limits the rate, above point Y increases have no further effect unless another factor changes.

Carbon Dioxide Concentration (as a limiting factor)

Level of CO₂ around the leaf; when low, it restricts photosynthesis even if light is abundant.

Temperature (as a limiting factor)

Environmental heat level; affects enzyme activity involved in photosynthesis, hence the overall rate.

Cuticle

Waxy, transparent layer on upper and lower epidermis that reduces water loss yet allows light to penetrate.

Upper Epidermis

Single layer of closely packed cells without chloroplasts; forms protective surface beneath the cuticle.

Lower Epidermis

Bottom leaf layer containing most stomata and guard cells; regulates gas exchange.

Stomata

Pores in the epidermis through which CO₂ enters and O₂ & water vapour exit; size controlled by guard cells.

Guard Cells

Specialised epidermal cells with chloroplasts that regulate stomatal opening by altering turgor pressure.

Palisade Mesophyll

Vertically aligned, tightly packed cells rich in chloroplasts; main site of photosynthesis in the leaf.

Spongy Mesophyll

Loosely arranged cells with fewer chloroplasts and large air spaces to facilitate gas diffusion.

Intercellular Air Spaces

Gaps within spongy mesophyll connecting to stomata, providing rapid diffusion pathways for gases.

Vascular Bundle

Leaf vein containing xylem and phloem for transport of water, minerals, and assimilates.

Xylem

Vascular tissue that conveys water and mineral salts from roots to mesophyll cells.

Phloem

Vascular tissue that transports sucrose and other organic nutrients away from the leaf.

Turgid (guard cells)

State when guard cells absorb water, swell, and open the stomata (daytime).

Flaccid (guard cells)

State when guard cells lose water, shrink, and close the stomata (nighttime).

Destarching

Keeping a plant in darkness (≈48 h) to use up stored starch before an experiment.

Iodine Test for Starch

Laboratory test where iodine solution turns blue-black in the presence of starch within a leaf.

Potassium Hydroxide (KOH) in Experiments

Chemical placed with leaves to absorb CO₂, demonstrating its necessity for photosynthesis.

Sodium Hydrogencarbonate Solution

Dilute baking-soda solution used to supply additional CO₂ to aquatic plants during rate investigations.

Sucrose Transport

Conversion of glucose to sucrose in leaves followed by movement through phloem to storage organs.

Respiration (in plants)

Process using glucose and O₂ to release energy; occurs continuously, unlike photosynthesis.

Glucose Uses in Plants

Respiration fuel, conversion to starch, sucrose, fats, amino acids, and proteins.

Nitrates (plant nutrition)

Soil ions absorbed via xylem and combined with glucose in leaves to form amino acids.

Fossil Fuels & Photosynthesis

Energy stored in coal, oil, and gas originates from ancient photosynthetic organisms.