the stem is bending towards the light

2.81 phototropism

light --> growth --> towards light
if theres light going in every direction the stem will grow upwards
if theres lateral light the stem will grow towards the light making it bend towards the light
auxin is a hormone which causes more growth --> growth in the stem

2.54 transpiration

for evaporation to occur we need water (liquid) to gas we need heat which is provided from the sunlight as the light is absorbed by the leaf structure

the evaporation is through the stomatal pores

light energy converted to heat as the structure of the leaf absorb the light

sunlight is coming down for photosynthesis and not all of it is absorbed by the chroloplast because some will absorb by the other cell sturcture which will generate some heat

the water vapour gas difuses through the pores by diffusion gradient

sunlight warms the leaf then the liquid transform to gas due to heat then the diffusion of the stomatal pore occurs 

diagram of a potometer

 

this is an experiment to demonstrate how the rate of transpiration of plants.

1. use a sharp blade to cut a lead

2. insert the leaf through the hole of the stopper ( which is provided with the potometer)

3. fill the potometer with water and fit the stopper holding the leaf

4. use vaseline to seal all the connections of the apparatus

5.trap an air bubble in the capillary tube by the following procedures:

• dip the end of the capillary tube into a beaker of water

· close the tap of the reservoir,

• take away the beaker of water and allow the plant to transpire for a while
• re-immerse the capillary tube into the beaker of water

6. wait for about 5 minutes for the plain to equilibrate

7. estimate the rate of transpiration by measuring the distance moved by the air bubble per unit time.

8. repeat the experiment and find the average

potometer

diagram of a root

2.53 roots structure