Photosynthesis
Photosynthesis happens in chloroplasts, using light energy (captured by chlorophyll) to convert carbon dioxide and water into glucose and oxygen: .
Example 1: State three factors that can limit the rate of photosynthesis.
Light intensity, carbon dioxide concentration, and temperature can all limit the rate -- whichever of these is in shortest supply relative to the plant's needs becomes the "limiting factor" holding back the overall rate, even if the other two are abundant.
Plant transport systems
Xylem carries water and dissolved minerals in one direction only: upward from the roots to the leaves. Phloem carries dissolved food (mainly sugar made in photosynthesis) in both directions -- from wherever it's made or stored to wherever it's needed for growth or storage, a process called translocation.
Transpiration
Transpiration is the loss of water vapour from a plant's surface, mostly through stomata on the leaves. It's a side effect of gas exchange -- stomata must open to let in for photosynthesis, and water vapour escapes through the same openings. Transpiration rate increases with higher temperature, lower humidity, more wind, and more light (which opens stomata wider).
Example 2: A plant loses water faster on a hot, windy, sunny day than on a cool, still, cloudy day. Explain why, in terms of transpiration.
Heat and wind both speed up the diffusion and removal of water vapour from the leaf surface, and light causes stomata to open wider for photosynthesis -- all three factors combined increase the transpiration rate, so the plant loses more water in the same amount of time.
Flower structure and pollination
A typical flower has petals (often colourful, to attract pollinators), sepals (protect the bud), stamens (the male part, producing pollen), and a carpel/pistil (the female part, containing the ovary and ovules). Pollination can be by insects (bright petals, scent, nectar) or by wind (small, dull flowers producing large amounts of light pollen).