Biology: B6 - Photosynthesis and plant hormones

what is photosynthesis

a chemical reaction that produces plant food (glucose)

what do plants need for photosynthesis

• water

• sunlight

• carbon dioxide

what are the products

glucose and oxygen

why are glucose and oxygen needed

for respiration (release of energy)

how are gases exchanged at the leaf

• carbon dioxide diffuses into the leaf, because there is a higher concentration of it outside than inside.

• oxygen is produced in photosynthesis and diffuses out of the leaf through the stomata

how is a leaf adapted

• petiole - used to move the leaf towards the sun

• chloroplasts - site of photosynthesis

• stomata - allow gases in and out

• thin - diffusion happens easily

• xylem and phloem carry water and glucose

photosynthesis word equation

carbon dioxide + water → glucose + oxygen

photosynthesis balanced equation

6CO2 + 6H20 → C6H12O6 + 6O2

what is the palisade mesophyll

• very thin so gasses can pass through easily

• lots of chloroplasts to absorb light energy

what is the waxy cuticle

• prevents water loss

• transparent to let light through

• large surface area

what is the spongy mesophyll

air spaces allow gases to be absorbed or for them to leave

what is the guard cell

• control the stomata

• turgid - firm - open stomata

• flaccid - soft - closed stomata

what is the stomata

open and close to let gases in and out

what is glucose needed for and where is it stored

• immediate energy source for respiration

• to make cellulose (cell wall)

• starch because its soluble

• stored in sucrose (fruit)

• stored in fats (seeds)

• growth and repair

algal balls practical vairables

• independent - distance away from light source

• dependent - PH

• control - volume of indicator, starting PH, number of algal balls

xylem cells

• dead cells

• carries water and minerals

• cell wall made of lignin

• no cytoplasm

• one way

phloem cells

• living cells

• carries glucose to growing parts or storage organs

• cell wall made of cellulose

• permeable cell walls

• bidirectional

transpiration

• water is absorbed by roots, travels through plant, evaporates from surface

• occurs in xylem cells

translocation

• occurs in the phloem cells

• carrying glucose from one place in the cell to another

when is a potometer used to measure

the rate of transpiration

what are the 4 factors that may increase the rate on transpiration

• humidity

• wind

• sunlight

• temperature

how are plants in deserts adapted

• small surface area:volume ratio

• cacti have spines instead of leaves to prevent water loss

• small leaved or folded leaves to reduce evaporation

marram grass

• waxy cuticle - reduces water loss through evaporation

• sunken stomata - reduce water loss through transpiration

• rolled leaf - to protect the stomata from the wind

plant hormones

• a chemical produced in plants to control their response to stimuli

• auxins are plant hormones responsible for growth responses

• auxins are produced in the shoot tips and root tips

what are the three things a plant will react to

• water

• light

• gravity

what is tropism

the stimuli

phototropism

the response to light

hydrotropism

the response to water

geotropism/gravitropism

the response to gravity

negative tropism

growing away from the stimulus

positive tropism

growing towards the stimulus

stimulus growth in shoots

• the hormones collect on the lower side

• it grows more and bends upwards away from the force of gravity

retards growth in roots

• hormones collect on the lower side

• slows down growth

• root grows downwards towards gravity

gibberellins

• controls flower and fruit foundations

• produce seedless fruit

• controls seed germination

• improves fruit quality

ethene

• ripening hormone

• influences growth by controlling cell division

• fruit is picked when unripe to prevent damage

• ethene gas is added to start ripening process