2.81 Phototropism

• phototropism = growth responses towards light
• If light is coming from all directions, the stem will grow upwards
• If the light is coming from one side (lateral light source), the stem bends towards the light
• The light on one side causes the movement of auxim (plant hormone), which causes the bending of the stem

2.80 geotropism

• geotropism = growth responses to gravity
• positive geotropism = when the stem of a seed grows downwards
• negative geotropism = when the stem of a seed grows upwards
• If you were to rotate the seed, the negative geotropism grows upwards, and the embryonic root will grow downwards showing positive geotropism.

2.79

• stimuli - changes in the environment, temeperature changes, light changes
• Receptors detect these stimuli, which makes it respond
• Responses are usually growth (tropism) e.g. the response to light being stimulated would be called phototropism
• A response to gravity is called a geotropism
• Connection between receptor and response is usually plant hormones (plant growth regulators) e.g. auxin

2.54 Transpiration

2.54 Transpiration
• Where water turns from a liquid into a gas, which requires heat
• Heat is supplied by sunlight
• Evaporation (liquid to gas) happens through the stomatal pores in the leaves
• Water vapor gas diffuses through the stomatal pore into the atmosphere

potometer

A potometer is used to measure the rate of water uptake of a plant

2.53 Root Structure

• The root structure has a branching pattern which increases the amount of water absorbed and the surface area of the root.
• There is a root hair in the root that contains of epidermal cells (surface) 
• the root hair concentrates minerals inside the root, which encourages the take of water by osmosis
• osmosis = water enters dilute region and goes to the epidermal cell, concentrated region
• Water travels from the root to the xylem using osmosis