Oxygen is a product of photosynthesis, not a raw material. Plants take in CO₂ and H₂O and use light energy to produce glucose and release O₂. Remember raw materials vs products.

Leaves have large surface area, chlorophyll-rich mesophyll cells and stomata for gas exchange — all necessary features for efficient photosynthesis.

Chlorophyll absorbs red and blue light and reflects green light, making leaves appear green. Other pigments exist but chlorophyll dominates in healthy green leaves.

Carbon dioxide is fixed during the Calvin cycle to form glucose. Oxygen is released as a byproduct.

Chlorophyll captures light energy and initiates the light-dependent reactions. Starch and glucose are products or storage forms, not pigments.

Photosynthesis stores solar energy in glucose molecules. It occurs mainly in leaves during daylight and consumes CO₂ rather than releasing it.

Plants often convert glucose into sucrose for efficient transport in phloem. Oxygen and water are not transported as food in phloem.

Broad, flat leaves provide more area to capture sunlight, increasing photosynthetic capacity. Cuticle reduces water loss but doesn't increase surface area.

Palisade cells are packed with chloroplasts and are arranged to capture maximum light. Spongy mesophyll aids gas exchange but has fewer chloroplasts.

Stomata allow CO₂ in for photosynthesis and let O₂ and water vapour out; guard cells regulate opening to balance gas exchange with water conservation.

Guard cells become turgid by taking in water (in light) and open the stomatal pore; loss of turgor closes it. This is a turgor-driven mechanism.

Veins (containing xylem and phloem) transport water/minerals and food and also provide structural support across the lamina.

Spongy mesophyll has air spaces facilitating diffusion of CO₂ to palisade cells and O₂ out; it assists gaseous exchange within leaf tissues.

The cuticle is a waxy, waterproof layer that reduces water loss and protects against pathogens; it's not cellular like epidermis beneath it.

Thin leaves ensure light reaches internal cells and gases diffuse quickly to photosynthesising cells; thickness would limit these processes.

Xylem vessels are dead, hollow, lignified tubes that transport water and minerals upwards. Phloem transports food, not water.

Transpiration creates a pull that helps draw water and minerals up through xylem and also cools leaves by evaporative loss.

Low temperature reduces evaporation rate, lowering transpiration. Low humidity increases transpiration; wind and bright sunlight also increase it.

Guttation occurs when root pressure forces water out through special pores (hydathodes), usually at night when transpiration is low.

Root pressure results from active ion uptake and osmotic water entry; it's often visible at night when transpiration is low, causing guttation or sap exudation.

Phloem sieve tubes and companion cells move sugars and other organic solutes between sources and sinks; xylem transports water and minerals.

Sugars are loaded into phloem at sources, water enters osmotically creating high pressure that drives sap toward sinks where sugars are unloaded, lowering pressure.

Companion cells are living cells that support sieve tubes metabolically and help in loading/unloading sugars into phloem for translocation.

Girdling removes phloem, interrupting downward movement of sugars; xylem remains, so water transport continues but roots are starved of food.

Source tissues (e.g., mature leaves) export excess sugars; sinks import them. Young leaves may be sinks if they consume more than produce.

Respiration breaks down glucose to release energy; CO₂ (and water) are byproducts. Oxygen is consumed during aerobic respiration.

Under oxygen-poor conditions (e.g., waterlogged soil), some organisms ferment glucose producing ethanol and CO₂; this gives less energy than aerobic respiration.

Plants do not have specialized organs for urine-like filtration. They excrete wastes via stomata, shedding parts, storing in vacuoles, or secreting resins.

Oxygen produced diffuses out of leaf cells into air spaces and exits via stomata. Roots and vascular tissues are not primary routes for gas release.

Plants sequester harmful substances in vacuoles, bark or leaves and later discard them; animals' kidney-like excretion does not occur in plants.

Saprophytes (mainly fungi) feed on dead organic matter by secreting enzymes and absorbing the nutrients; they are not photosynthetic autotrophs.

Cuscuta lacks sufficient chlorophyll and obtains water and nutrients from host plants, classifying it as a parasitic plant.

Carnivorous plants supplement nitrogen and other minerals by digesting insects, which is vital in nutrient-poor soils.

Thick cuticle, reduced leaf area, sunken stomata and succulence are xerophytic features reducing transpiration and conserving water.

Iodine reacts with starch to give a blue-black colour; this test demonstrates that photosynthesis has produced and stored glucose as starch in leaf tissues.

Stomata are usually more abundant on the lower surface; peeling the lower epidermis and viewing under microscope reveals guard cells and stomatal pores.

Potometers measure the amount of water taken up by a shoot; it is used as an indirect measure of transpiration under experimental conditions.

Alcohol removes chlorophyll so the iodine-starch colour change is visible. Boiling in water beforehand kills tissue and breaks cell membranes for better alcohol penetration.

Water vapour lost from leaf transpires and condenses on the bag surface, visible as droplets, demonstrating transpiration.

Phloem transport is described as source to sink where sugars move from regions of production to regions of use/storage. Direction can vary depending on plant stage (e.g., roots can be source in spring).