3.4 Plant Fertilisation

• So here we have the pollen grain on the stigma and what happens is they germinate, the tube begins to grow like this. Tend species specific, pollen tube will complete if its the same species.
• This diagram we can see the pollen tube all the way down and round to the ovule here coloured yellow.
• So, descend through the pollen tube. Moves the nucleus, male nucleus travel down here and into the ovule.
• There are number of things will occurred:

1. Pollen nucleus will fertilise the ovule and the fermentation of a zygote and this in term will grow into the embryo.
2. The outside of the ovule form the seed coat called "Testa".
3. The cotyledons is the food stores for the seedling which support plant for their first set of leaves.
4. Will form fruits from the wall of ovary and carpel.

3.3b Wind Pollination

• The transferred of the pollen grain from the anther to the stigma through air carry by the wind.
• Pollen grains first adaptations is to have light weight, wings features which allowed to move through the air more efficently. Secondly we were expect to find the anther will hang well clear, anther will expose to the wimnd.
• Third feature which related to the stigma, we would expect the stigma has large surface area a kind of feather like structure to catch the pollen grain.
• They pass through the air on the wind wich will be caught on the stigma structure here.
• If we look at the image here f the grass no colour, no scent, no nectaries and no point of producing sugar which is the waste of energy for the grass which the wind that pollinated the plant and the adaptaions are light pollen grain, exposed anthers and exposed stigma.

3.3a Insect Pollination

• In the process of pollinating of flower, there must be a transferred of pollen grains from the anther of one plant to the stigma of another.
• Pollen is the small structure which contain the male nucleus and the transferred in an insect pollinated plant is take places by insects.
• So, its necessary for this type of flower to attract insect into the first flower and then have a reason to go to the second flower. If pollen goes to one plant to another we called it cross-pollination.
• Looking the single flower structure we found the adaptations to attract the insect, first of all we  might call signals which is in the inside which is colour petals, insect can see colours.
• Second thing are scents which flowers has which attract the insect so, insect can detect these molecules and be attract by the plants from the scents.
• A value to the inside of going into the flower which provide food which at the nectaries is producing a sugar called fructose, many insect will use the pollen itself to as a source of protein and the stamen is the male part of the plant and compose to the anther which is produce pollen grains and their on the stalk called the filament.
• So, the anther and the filament form the stamen and then the female is compose of 3 sections which are the stigma which pollen grains fall, style which connects to the stigma to the ovary which we can find the eggs called the ovules and this whole structure here is called a carpel that the female part and the stamen of the stamen. 

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.