Biology- (Topic 6) Plant Structures And Their Functions

Front 1

Photosynthesis

Back 1

Used to make glucose. Some glucose is used to make large complex molecules the plants/algae need to grow- these make up the organisms biomass, the mass of living material.

The energy stored in biomass then works its way through the food chain as animals eat them, so photosynthetic organisms are the main producers of food for nearly all life on earth.

Photosynthesis is an endothermic reaction.

Rate of photosynthesis is affected by light intensity, the concentration of co2, and the temperature l

Front 2

Core particle: effect of light intensity on the rate of photosynthesis

Back 2

1) pond weed placed in beaker full of water and sodium hydrogencarbonate (so there Is enough co2 and won’t be the limiting factor)

2)Place gas syringe on top to measure oxygen emitted.

3) place light source on a ruler and move after a set time.

Can also be measured by counting bubbles. Can be changed to measure temp by heating water, add more sodium hydrogencarbonate to measure CO2, only change 1 variable.

Front 3

Limiting factors in photosynthesis

Back 3

As light intensity increases, rate increases however it soon plateau out and when co2 or temp becomes a limiting factor. To plot: light intensity is inversely proportional to 1 / distance squared

Carbon dioxide is the same as light.

Temperature rises than falls as the enzymes start to denature.

Front 4

Transport in plants

Back 4

Root hairs take in minerals and water. The “hairs” stick into the soil and Increase tease surface area. The concentration of mineral ions is usually higher in the root hair cells than in the soil around them so mineral ions are absorbed by active transport and water is absorbed by osmosis

Plein transports fois, and is made of columns of elongated living cells with pored in the end walks to allow stuff to flow through.

Xylem takes up water and mineral ions. Are dead cells joined end to end with no end walls between them and a hole down the middle. Are strengthened with lignin.

Transpiration is the lois of water from a plant. Is caused by the evaporation and diffusion of water from the plants surface (usually leaves). Water is than drawn up to replace it- called the transpiration stream.

Front 5

Stomata

Back 5

Are tiny pores on the surface of plant, they allow co2 and oxygen to diffuse directly in and out of a leaf. Also allow water vapour to escape during transpiration.

Stomata are surrounded by girafe cells which change shape to control size of pore- open when turgid and closed when flaccid.

Front 6

Transporation

Back 6

Affected by these environmental factors:

1) light intensity- the brighter the light, the greater the transpiration rate.

2) temperature- the warmer it is the faster transpiration happens, as water particles have more energy to evaporate and diffuse out of the stomata.

3)air flow- the better air flow around the leaf, the faster transpiration happens, as the water vapour moves away from he leaf quickly.

How to measure it: see hint

Hint 6

Front 7

Adoption of leaves and plants

Back 7

Leaves are broad so large surface area to get lots of light for photosynthesis

The palisade leader has lots of chloroplasts, so are near the top to get lots of light.

Upper epidermis is transparent so light can get through to palisade layer.

The xylem and phloem produces water for photosynthesis and take away glucose produced.

The epidermal tissues are covered with a waxy cuticle that reduces water loss by evaporation.

In hot environments:

Small leaves or spines reduce surface are for water loss by evaporation and spines fend of animals.

Curled leaves reduces air flow close to leaf, which traps water vapour nearby.

Thick waxy cuticles reduce water loss by evaporation.

A thick, fleshy stein stores water

Fewer stomata or stomata that only open at night reduce water loss by evaporation.

Stomata in sunken pits reduces air flow, meaning more water vapour.

Front 8

Plant hormones

Back 8

Auxins are plant growth hormones. Is produced in tips and diffuses backwards to stimulate cell elongation. Promotes growth in shoot but stops growth in root.

Shoots are positively phototropism as they grow towards light. This is because when exposed to light, auxins accumulate more auxins in the side in the shade, making that side grow faster and therefore bend to the light.

Shots are negatively gravitropic, as when a shoot grows sideways gravity causes an unequal distribution of auxin in the tip, with more auxin on the lower side, which causes the lower side to grow faster and bend upwards.

Roots are Positively gravitropic. As auxin inhibits growth, top side grows fast and bends downwards.

Roots are negatively phototropism as the grow away form light, as if a root is exposed to some light more auxin accumulates on the more shaded side, and the auxin inhibits growth on shaded side so bends downwards

Front 9

Commercial uses of plant hormones

Back 9

1) selective weed killers: most weeds are broad weeds whilst grasses and cereals have very narrow leaves, so selective weedkillers have developed to only affect broad leave plants. They work by disrupting their normal growth patterns which soon kills them.

2) growing from cuttings with root powder: a cutting is stuck in the soil (where normally they wouldn’t grow) but if you ass rooting powder which contains auxins, they produce roots, enables growers to produce lots of clones very quickly.

3) controlling flower and fruit formation:gibberellins are plant hormones that stimulate seed germination, stem growth and flowering. Can be used to cause plants to flower or not to. Also used to reduce flower formation which can improve fruit quality.

4) producing seedless fruit: fruit with seeds only grow on flowering plants which have been pollinated, if the flower doesn’t get pollinated no fruit and seeds grows. If plant hormones such as gibberllines are applied to the unpollinated flower, fruit will grow but not the seeds.

5) controlling the ripening of fruits: can be controlled either while they are still on plant or being transported. A ripening hormone called ethane is added and the fruit will ripen on way to supermarket.

6) controlling seed germination: lots of seeds won’t germinate until they’ve been through certain conditions. Seeds can be treated with gibberellins to make them germinate at times of year that they wouldn’t normally. Also means all seeds in a batch will germinate at same time.

Front 10

Commercial uses of plant hormones

Back 10

1) selective weed killers: most weeds are broad weeds whilst grasses and cereals have very narrow leaves, so selective weedkillers have developed to only affect broad leave plants. They work by disrupting their normal growth patterns which soon kills them.

2) growing from cuttings with root powder: a cutting is stuck in the soil (where normally they wouldn’t grow) but if you ass rooting powder which contains auxins, they produce roots, enables growers to produce lots of clones very quickly.

3) controlling flower and fruit formation:gibberellins are plant hormones that stimulate seed germination, stem growth and flowering. Can be used to cause plants to flower or not to. Also used to reduce flower formation which can improve fruit quality.

4) producing seedless fruit: fruit with seeds only grow on flowering plants which have been pollinated, if the flower doesn’t get pollinated no fruit and seeds grows. If plant hormones such as gibberllines are applied to the unpollinated flower, fruit will grow but not the seeds.

5) controlling the ripening of fruits: can be controlled either while they are still on plant or being transported. A ripening hormone called ethane is added and the fruit will ripen on way to supermarket.

6) controlling seed germination: lots of seeds won’t germinate until they’ve been through certain conditions. Seeds can be treated with gibberellins to make them germinate at times of year that they wouldn’t normally. Also means all seeds in a batch will germinate at same time.