Biology: Plants tissues,organs and systems

Leaves 

• the site of photosynthesis
• contain chloroplasts which contain chlorophyll

Flowers

• sexual reproduction
• male and female parts

Roots

• used for anchorage
• site where water moves in by osmosis

Stems

• transports water from roots
• to the leaves and flower

Root Hair Cells

• very thin, hair-like structures that cover the length of the root
• they have a large surface area to maximise the amount of water that can move in at once
• thinner cell wall - shorter diffusion distance

Osmosis

• movement of water across a semi-permeable membrane
• high to low concentration of water (down a concentration gradient)
• passive process

The soil is hypotonic and water moves into roots by osmosis. they take in minerals by diffusion until equilibrium is reached. active transport takes over as the soil is now hypertonic.

plants need

• magnesium: produce chlorophyll. if deficient can get chlorosis. 
• nitrate: makes proteins. reduced growth if not enough.

Not enough water: plasmolyzed and hypertonic

full of water: turgid and hypotonic 

Xylem

• dead cells
• water-proof lignin
• water and minerals
• from roots to leaves

Phloem

• transports sugars (glucose and sucrose)
• organic molecule
• living cells
• sieve plates

• mostly responsibility for photosynthesis

structure:

• waxy cuticle,
• upper epidermis,
• palisade mesophyll,
• spongy mesophyll tissue,
• vascular bundle,
• air spaces,
• stomata,
• guard cells and lower epidermis.

stomata- pores in leaf mostly on the under-surface, guard cells can open and close the stomata

1. water moves into the roots, from the soil by osmosis

2. water moves up the stem into the leaves

3.water is lost by evaporation from open stomata

measuring transpiration rate:

• potometers- a tube with a reservoir feeding through it and a scale with an air bubble at zero feeding into a beaker of water.

factors that affect the transpiration rate- temp, light intensity, humidity, air movement