SB6 Plant Structures and their Functions Flashcards
Photosynthesis Equation
6CO2 + 6H20 —> C6H1206 + 6O2
Why is photosynthesis endothermic?
Because it takes in energy from the surroundings, such as light
Plant adaptations for photosynthesis
Chloroplasts contain chlorophyll which absorbs light
What does glucose do in a plant?
Used to make larger, complex molecules that the plant needs to grow and makeup the organism’s biomass
Define rate of reaction
The speed at which the reaction is occurring
How does temperature affect the rate of photosynthesis?
Enzymes work slow at lower temperatures. But if the plant gets too hot, the enzymes will denature. If the enzymes are at the optimum temp., then something else is the limiting factor
How does light intensity affect the rate of photosynthesis?
Light transfers the energy needed for photosynthesis. If the reaction has plenty of light, then it will react up to a certain point before something else is the limiting factor
How does carbon dioxide concentration affect the rate of photosynthesis?
CO2 is needed for photosynthesis. Increasing the amount of CO2 you have increases the rate of reaction, up to a point. Then something else becomes the limiting factor
List the limiting factors to photosynthesis
temperature, light intensity and carbon dioxide concentration
Why is the rate of photosynthesis indirectly proportional to the distance of a light source?
The closer the light source, the greater the light intensity.
What is the impact of more than one factor on the rate of photosynthesis?
The temperature must be just right, too little CO2 slows it down, and not enough light also slows down the rate of photosynthesis. All factors must be perfect
Root hair cell adaptations
Cells on surface of roots grow into “hairs” that sick out into the soil. Each branch is covered with microscopic hairs. This gives plant large SA to absorb mineral ions and water
Define a concentration gradient
An area of higher concentration to an area of lower concentration
How do molecules move by osmosis? eg in root hair cells
Water is absorbed by osmosis as it goes from the soil which is has a higher concentration of water, across the cell membrane to an area of lower concentration
Define transpiration in plants
Transpiration is caused by the evaporation and diffusion of water from a plant’s surface, so more water is drawn up the xylem to replace this, creating a constant transpiration stream
Define translocation in plants
Happens in phloem tubes transporting food substances
Xylem adaptations
- made of dead cells joined end to end with no end walls between them and a hole down the middle
- they’re strengthened with a material called lignin
- carry water and mineral ions from roots to stem and leaves
Phloem adaptations
- made of columns of elongated living cells with small pores in the end walls to allow stuff to flow through
- transport food substances (sucrose) made in the leaves to the rest of the plant for immediate use or for storage
Environmental factors effecting the rate of transpiration
Light intensity - brighter light, greater transpiration rate
Temperature - the warmer it is, the faster transpiration happens
Air flow - better the air flow around a leaf, greater transpiration rate
How do you measure the rate of transpiration?
A potometer measures water uptake by a plant, but it’s assumed that water uptake by the plant is directly related to water loss from the leaves
Define stomata
Stomata are tiny pores on the surface of a plant, mostly found on the lower surface of leaves, allowing CO2 and O2 to diffuse directly in and out of a leaf
Adaptations go a cactus
- small leaves / spines reduces SA
- curled leaves or hairs on surface reduces air flow
- thick waxy cuticle reduces water loss by evaporation
- thick fleshy stem stores water
- fewer stomata / stomata that only open at night reducing water loss
Adaptations to a leaf
- upper epidermis is transparent so light can pass through
- palisade layer has lots of chloroplasts
- epidermal tissues are covered with waxy cuticle
Define tropism
A tropism is a growth response to a one sided stimulus
How is fruit artificially ripened?
The fruit is picked unripe and then a ripening hormone (ethene) is added in transportation
How are gibberellins used?
1) Seeds can be treated with gibberellins to make them germinate at any time of year
2) Gibberellins are applied to unpollinated flowers, the fruit will grow but seeds won’t
3) Used to control plant hormones that stimulate seed germination, so it can control flower and fruit formation
Shoots grow towards the light
POSITIVELY PHOTOTROPIC
When exposed to light, more auxins accumulate on the side that’s in the shade, making the cell grow (elongate) faster on the shaded side, causing it to grow towards the light
Roots grow away from light
NEGATIVELY PHOTOTROPIC
If a root is exposed to some light, more auxins accumulate on the shaded side. The auxins inhibit cell elongation on the shaded side, so the root bends back down into the ground
How are auxins used?
1) Selective weed killers only affect broad-leaved plants and don’t disrupt crops and grass
2) Adding auxins to parts of a plant you have cut off will make it produce roots and grow into a new plant
Advantages of using hormones in fruit farming
Control when the seeds grow, when they ripen, whether they have seeds
