2.55 Rate of transpiration

• Water lost from leave due to humidity, wind speed, temperature and light intensity. So, if we return to transpiration is the lost of water through the leave is cause by evaporation.
• The absorption of the sunshine generate the heat which transformed the water here in the leave into the gas face here above the Stamata pores, and then the important thing is the diffusion through the pores, so we need to think about the diffusion gradient from inside the pore in this region here and this region here. So, we call this one A and this one B.
• So, the concentration gradient for water vapor, if there’s a big different then we would have high rate of transpiration, if we the difference between A and B is small then we will have a low rate of transpiration.
• So, the factors that would cause a large different would be for instance if the humidity here is very low, and the second one would be if the wind blows away the water vapor here, that will keep the different large so, high wind.
• If the temperature is high will get more evaporation so, high temperature and the fourth one is light intensity so, if high light intensity will have high rates of photosynthesis and water movement.
• Low humidity, high wind, high temperature and high light intensity will all lead to large different in the concentration in A and B which will result in fast diffusion and high rate of transpiration.
• Conversely, if the different is small between A and B where humidity is high , where the wind speed is low, so high humidity around the Stamata pores the different will be small, the rate of diffusion will be small.
• If the wind speed is low that water vapor would built up around here, and the gradient is shallow, small again so that would be low rate of transpiration.
• Three low temperatures, low rate of evaporation and that will result a small different low rate but low light intensity and the rate of photosynthesis would be and slow and low. So the key features of understanding the rate of transpirations are the different between the concentration of the water here and here.
•  And how humidity, wind speed, temperature and light intensity effect transpiration depends on creating small and large differences here.

2.81 Phototropism

• Phototrpoism means photo is light and tropism is growth in response to this light, and the positive is a growth towards the light.
• So we considered this in stem so, let take the tip of the stem and draw that with a simple structure like this and uniform light coming from all directions it would grow forwards and upwards.
• However, if we present the same stem tip with light from the side so, the lateral light source what happens is that the plant bends in the growth towards that light band.
• So, this is an example of positive phototropism growth of the stem towards the light.
• The understand of this the light on this side causes the movement to the opposite side of a compound known as "Auxin" which is a plant hormones which causes more gorwth and on this side and this side causes more bending.

2.80 Geotrpism

• Geotropic means geo is gravtiy and tropic is a growth responses so, its a growth responses to gravity.
• Example is take a seed and we arbsorb the seed growing we find the embryonic roots all grow downwards this is describe as positive geotropism.
• Where is the embryonic should grow upwards towards the soil surface and this is negative geotropism.
• Further experiment involve taking the same germinating seed turning it as shown so, it been rotated.
• Then what we see is that the shoot would then grow upwards and show the negative geotropism again and the embryonic root will turn and grow downwords the root positive geotropism.

2.79 Plants and Stimuli

• Stimuli are changes in the environment like temperature changes or light changes.
• The plants has receptor which can detect these stimuli and then turn this into responses often take the form of growth.
• This type of response growth in response to stimuli is called a tropism.
• Tropism that involve light is called a "phototropism" and another one is tropism involve to gravity which is called a "geotropism".
• The connection between the receptor and the response is usually take to form of plant hormones, sometimes called plant "growth regulaters". An example we will looking at later is Auxin.

2.54 Transpiration

• Liquid to gas need heat to do that , heat is provided by sunlight as it arbsorb by the leave structure .
• The light energy is converted to heat as the structure of the leave arbsorb the light.
• The liquid water will turn to a gas and the evaporation is throught the stomatel pores.
• The water taken up by the roots system by the osmosis travels up to the stem out to the petial and evaporation of water throgh the stomatel pores. Sunlight warming the leave creating the heat for the change in water for the liquid to a gas so, it can escape by evaporation.
• Not all of that light would be arbsorb by the chloroplast some would be arbsob by the other cells structure would generate some heat.
• The water was been delivered to the leave here from the xylem move through the spongey misel fill and just above stomatel pore is that the face change occured from liquid to gas evaporation then what occur the water vapour gas diffuses  through the pore.
• Than a fairly steep diffusion gradient so, the sunlight warm the leave and the second thing is the change of the water from the liquid face into the gas face and the third thing is the diffusion of the water vapour  through the stomatel pore.

2.53 Root Structure

• Branching pattern increasing the surface area for the arbsorbtional of water.
• The root will branch out and try to find the water source.
• Smallest end of the roots for the epidermal cells appear to be hair which is called "root hairs".
• The active transport is the mains movement for atcive minerals.
• Plant take up water by osmosis recall in osmosis is the water moves by the dilute region to concentrated reigen and thats the movement of water, the dilute region is the soil water surrounding the root hair and the concentrating reigen is created by building up the minerals inside the cells. That's achieve by active transport, so it's a two part process active transport of minerals and osmosis of water, water then move across the cortex of the root to the xylem again by osmosis.