Topic 6- Leaf adaptations and plant hormones Flashcards
How are leaves adapted for photosynthesis and gas exchange?
Leaves are broad, so theres a large surface area exposed to light which is needed for photosynthesis
How is palisade layer adapted for photosynthesis and gas exchange?
The palisade layer is near the top of the leaf as it has lots of chloroplasts to get the most light for photosynthesis.
How is upper epidermis adapted for photosynthesis and gas exchange?
It is transparent so that light can pass through it to the palisade layer.
How is the waxy cuticle adapted for photosynthesis and gas exchange?
It is waterproof which reduced water loss by evaporation
How are the tissues of leaves adapted for photosynthesis and gas exchange?
the lower epidermis has lots of stomata which allows carbon dioxide to diffuse directly into the leaf and the spongy mesophyll tissue has air spaces which increases the rate of diffusion.
Explain how 3 features of cacti that are adapted to help it live in extreme environments
1) Small leaves or spines reduce the surface area for water loss by evaporation. Spines also prevent animals eating the plant for water
2) A thicc, fleshy stem to store water
3) Fewer stomata or stomata that only open at night reduce water loss by evaporation
What are auxins?
They are plant hormones that control growth at the tips of the shoots and roots. They move through a plant in solution. They stimulate cell elongation. They promote growth in the shoots but inhibit it in the roots.
Name and explain the part of the plant that is positively phototrophic
Shoots grow towards light- when a shoot tip is exposed to light, it accumulates more auxins in the side that’s in the shade. This makes the cells elongate faster on the shaded side so the shoot bends towards the light. This means it will be more able to absorb light for photosynthesis.
What do shoots growing in the complete dark look like?
tall and spindly
Name and explain the part of the plant that is negatively gravitropic
Shoots grow away from gravity- when a shoot is growing sideways, gravity produces more auxin in the lower side making it grow faster and bend upwards.
Name and explain the part of the plant that is positively gravitrophic
Roots grow towards gravity- a root growing sideways will have more auxins on its lower side but in the roots auxins inhibit growth so the cells on the top will grow faster and bend the root downwards.
Name and explain the part of the plant that’s negatively phototropic
Roots grow away from light- if a root is exposed to light, more auxin accumulates on the shaded side which inhibits elongation on that side so the root bends backwards into the ground.
How are plant hormones used in selective weedkillers?
most weeds growing in fields are broad-leaved, selective weedkillers have been developed from auxins which only effect broad-leaved plants. They disrupt their growth pattern, killing them and leaving grass/crops untouched
How are plant hormones used in growing from cutting and root powders?
A cutting is a part of a plant that has been cut off. Normally, if you stick cuttings in soil, they wont grow unless you add root powder that contains auxins. They will produce roots rapidly and start growing as new plants. This enables growers to produce clones easily.
How are plant hormones used in controlling fruit and flower formation?
Gibberellins are plant hormones that stimulate seed germination, stem growth and flowering. They can be used to make plants flower earlier or in conditions they wouldn’t usually.
They can also be used to reduce flower formation because fruits grow from flowers. If there are too much flowers then lots of fruit grow but they’ll be small so the trees can support it. The less flowers, the less fruit and the more nice and big they are.
