Topic 6- Plant Structures And Their Functions Flashcards
equation for photosynthesis
Carbon dioxide +water -> glucose + oxygen
how to investigate the light intensity
- a source of light is placed at specific distances from the pondweed
- the pondweed is left to photosynthesise for a set amount of time
- as the pond weed photosynthesises oxygen is released and will be collected in the gas syringe
what are the limiting factors of photosynthesis?
- not enough light
- too little carbon dioxide
- temperature too high or low
equation for light intensity
Light intensity ∝ 1 ÷ distance (d)²
root hairs
- absorb water and mineral ions in soil
- have millions of microscopic hairs
- large surface area
phloem tubes
- columns of elongated living cells
- they transport food substances (mainly sucrose)
- this is a process called translocation
- transport goes both ways
functions of xylem
- made of dead cells joined end to end
- strengthened with lignin
- they carry water and mineral ions from the roots to the stem and leaves
- this process is called transpiration stream
definition of transpiration
The movement of water from the roots, through the xylem and out of the leaves
stomata
- stomata are tiny pores on the surface of a leaf
- they allow for gas exchange
- surrounded by guard cells
what 3 environmental factors affect the rate of transpiration?
- light intensity
- temperature
- air flow
how are leaves adapted for photosynthesis?
•broad leaves
Increase surface area to get more light for photosynthesis
•palisade layer has lots of chloroplasts
•upper epidermis is transparent
Let’s light pass through
•waxy cuticle
Reduce water loss
how are leaves adapted for gas exchange?
•stomata
-let’s carbon dioxide diffuse directly into the leaf
•spongy mesophyll
-has air spaces which increases the rate of diffusion
how are some plants adapted to extreme climates?
•small leaves
Reduces surface area for water loss
•curled leaves or hairs
Reduces air flow and traps water vapour
•thick waxy cuticles
Reduce water loss
•thick fleshy stem
which stores water
auxins
Plant hormones which control growth at the tip of shoots and roots
definition of positively phototropic
- grows towards light
- when a shoot tip is exposed to light it accumulates more auxin on the side which is in the shade
- it will then grow faster on the side which is shaded
- so it grows towards light
definition of negatively phototropic
- grows away from light
- if a root is exposed to light more auxin accumulate on the shaded side
- so the root grows downwards
definition of positively gravitropic
•grows towards gravity
definition of negatively gravitropic
•grows away from gravity
how to investigate the effect of light intensity on growth
- Canadian pond weed is put in a flask
- a light source is placed at a specific length away from the flask
- at a specific time see how much gas has been produced (gas syringe on top of the flask)
- repeat with different lengths
how do weedkillers work?
Selective weed killers have been developed from auxins, which only affect broad leaved plants
They disrupt their normal growth patterns
how are rooting powders used?
By cutting of part of the plant and adding rooting powder(contains auxins) it will then produce roots
This enables growers to produce clones
how are flower and fruit formation controlled?
Using gibberellins
A plant hormone that stimulates stem growth, seed germination and flowering
how are seedless fruit produced?
Adding plant hormones
Eg. Gibberellins
Some citrus fruit is grown like this
how is ripening in fruit controlled?
The fruit is picked unripe
Then ethane is added to ripen the fruit
