Food Production & the environment

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This creates a slight shortage of water in the leaf, which causes more water to be drawn up into the leaf from the rest of the plant

This in turn results in more water being drawn in through the roots

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Slide 19

Why is transpiration useful?

It transports minerals from the soil

It cools the plant

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Slide 20

What factors can affect the rate of water loss through stomata?

Temperature

Light

Air movement

Humidity

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Slide 21

Why do plants need minerals?

Plants need minerals for healthy growth

Large amounts of nitrates are needed for making proteins

Smaller amounts of iron and magnesium are needed to make chlorophyll

Leaves showing varying amounts of magnesium deficiency

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Slide 22

How do plants get their minerals?

Plants take up some dissolved mineral salts by diffusion

However, diffusion will not happen if the concentration of minerals in the soil is greater inside the root (which is usually the case)

If the concentration of minerals outside the root is lower than inside, then the root will take up mineral ions by active transport

These minerals are essential for a plants growth

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Slide 23

What is active transport?

Active transport allows the plant to absorb minerals against a concentration gradient

Energy is needed for active transport

The plant gets this energy from respiration

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Slide 24

What are plant hormones?

These are chemicals known as auxins

Auxins are plant growth hormones

They control the growing parts of the plant, I.e. the tips of shoots and roots

Auxins are made in the tips, they diffuse backwards are lilttle way, and cause cells to elongate just behind the tips

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Slide 25

How can we use plant hormones commercially?

We can put rooting growth hormone onto the end of a cutting to make new roots grow

This enables farmers to make clones of desirable plants very quickly

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Slide 26

Other uses for plant hormones

Killing weeds

Selective weedkillers have been developed using plant hormones

These weedkillers will broad-leaved plants (which are usually weeds)