Plantsss Flashcards
Hydrotropism in shoots
None
What is a tropism
The growth response of a plant to a directional stimulus
Hydrotropism in roots
Some grow towards direction of water (positive hydrotropism)
Phototropism in shoots
Grow towards light source (positive phototropism
Phototropism in roots
Most species show no response; some grow away from light (negative phototropism)
Geotropism in shoots
Grow against direction of gravity (negative geotropism)
Geotropism in roots
Grow towards direction of gravity (positive geotropism)
What is auxin
The hormone(plant growth substance) that is responsible for tropism
Why does a lack of nitrogen inhibit he growth of a plant
Nitrate ions needed For making amino acids which make proteins which are required for growth
Why are phosphate ions needed by plants
Making DNA
A plant deficient in phosphate will have poor root growth and younger leaves will turn purple
Why are potassium ions needed by plants
Needed for enzymes of respiration and photosynthesis to work
In plants lacking potassium, leaves turn yellow with dead spots
Why are magnesium ions needed by plants
Magnesium is needed for making chlorophyll for photosynthesis
The colour of this pigment is green and so plants that lack magnesium have yellow leaves
Why is starch a good way of storing carb
Not soluble
Compact
Can be broken down easily
Why can’t you test a fresh leaf for starch using iodine
The waxy surface won’t absorb the solution
Green colour of leaf masks colour change
How do you remove the outer waxy layer and decolorise a leaf
Place it in boiling ethanol
How can you de starch a leaf
Place it in the dark for 2 or 3 days
The plant uses up the starch stores in its leaves
How to stop co2 from getting to a plant
Place the plant in a closed container containing a chemical called soda lime - this absorbs co2 from the air around the plant
What does a clinostat do
Holds the plant and slowly rotates in a vertical plane, so that the movement eliminates any directional stimulus that may be acting on the seeds
Guard cell adaptation for function
‘Banana’ shape with thicker cell wall on inside (around) means that when the guard cells become turgid they change shape, bowing outwards, so opening the stoma for gas exchange
Only cells that don’t need osmosis to maintain their shape
Xylem cells
preventing water loss by having stomata in sunken pits in leaf
A region of humid air is trapped in the pit
This reduces evaporation through the stomata, conserving water in the plant
Lipids uses
Energy store in some plants eg nuts, seeds
Part of all cell membranes
