4.2.3.2 Plant organ system

What is translocation

The movement of food substances made in the leaves up or down the phloem for use immediately or storage

Transpiration

Lots of water or water vapour from the leaves and stems of the plant. It is a consequence of gassiest exchange as the smart are open that this can occur.

How does increasing temperature affect the rate of transpiration/evaporation

The molecules move faster, resulting in evaporation happening at a faster rate, and therefore the rate of transpiration increases

The rate of photosynthesis increases meaning most of water are open for gassiest exchange, so more water evaporate, and the rate of transpiration increases

How does the increase in relative humidity affect the rate of transpiration/evaporation

Is the relative humidity is high then they will be reduced concentration gradient between the concentrations of water vapour inside and outside the leaf resulting in a slower rate of diffusion. This will decrease the rate of transpiration

How does increased movement affect the rate of transpiration/evaporation

If more areas moving away from the leaf due to it being blown away, then the concentration of water vapour surrounding leave will be lower. This will mean there will be a steep a concentration gradient resulting in diffusion happening faster. This will increase the rate of transpiration.

Is increased light intensity affect the rate of evaporation/transpiration

This leads to an increase the rate of photosynthesis, so most tomato open to allow gaseous exchange to occur

This means more water can evaporate leading to an increase rate of transpiration

Potometer

Measuring the uptake of water by the plan, gives an indication to the rate of transpiration, because water is any taken up if water leaves the plant. This is observed by using a potometer which involves placing a plan in a tube of water, and measuring the distance, travelled by a bubble

Guard cells

* they are kidney shaped
* They have thin outer walls and thick inner walls
* When lots of water is available to the plant, the cells fill and change shape, openings stomata (They are also light-sensitive)
* This allows gases to be exchanged and more water to leave the plant via evaporation
* more stomata are found in the bottom of the leaf, allowing gases to be exchanged whilst minimising water loss by evaporation as the lower surface is shaded and cooler

what is transpiration stream

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The transpiration stream is the movement of water up the stem