2.20 How are leaves adapted to photosynthesis?

1. The blade or lamina of the leaf have a Large surface area which helps collect light.
2. Thinness of the leaf allows fast diffusion of gases such as Carbon Dioxide and oxygen.
3. The Palisade cells which contain the chloroplasts. It is located in the upper section of the leaf which makes it easier and faster for the light to penetrate through the cuticle and get trapped into the palisade layer.
4. There are many chloroplasts which contain the chlorophyll in the palisade cells. The palisade layer is a large surface which allows more light to be absorbed into the chloroplasts.
5. The stomatal pores are located in the lower epidermes which makes it faster for the Carbon dioxide to access it. These pores are formed by guard cells which can open and close. They're mostly open during the day, allowing carbon dioxide to enter.
6. mysophyll layer contain many spaces which allow diffusion of carbon dioxide and the movement of water.
7. The presence of the vascular bundle, the vein which comes into the leaf. This helps deliver water through the tissue, xylem, into the leaf, which transports water up through the mesophyll spaces up to the palisade layer.
8. At the end of photosynthesis when sucrose (sugar) is formed, it is then dissolved to form 'sap' which also moves up through the phloem, which is the tissue on the other side of the vascular bundle. This process is called translocation.

1. An experiment using an aquatic plant to show the production of oxygen due to photosynthesis.
2. The gas is collected over water.
3. There's a separate glass funnel which is fully submerged in water.
4. The oxygen will be collected in a testube which is filled with water. 
5. The testube is attatched to the end of the tube of the funnel. The testube is then lifted vertically therefore we have the wide part of the funnel submerged in water.
6. The aquatic plant is placed under the funnel.
7. As the plant photosynthesizes, the oxygen will travel upwards in the testube and displace the water at the top.
8. With time, the water will be replaced by oxygen gas in the testube.

2.19 Factors of the rate of Photosynthesis

1. The rate of photosynthesis is judged through how rapidly glucose and oxygen are produced.
2. The process of photosynthesis consists of an enzyme reaction.
3. As the concentration of Carbon Dioxide increases, the rate of photosynthesis increases up to a certain point after which it remains constant.
4. The increase within the concentration of light intensity, also triggers an increase in the rate of photosynthesis up to a certain level, after which the rate of photosynthesis becomes constant.
5. As the temperature increases more substrate molecules collide with the enzymes, causing a higher rat of photosynthesis. However, after the optimum temperature (the highest rate of photosynthesis considering temperature) the enzymes are denatured- kinetic theory.
6. When all three considerations for the rate of photosynthesis are combined, the slowest rate of all three combined convey the overall rate. This is known as the limiting factor.

2.18 Photosynthesis equations

1. Carbon Diooxide + water ----chlorophyll----light energy----enzymes---- glucose + oxygen.
2. Carbon Dioxide and water are the substrates whereas the glucose and oxygen are regarded as glucose and oxygen.
3. All of this occurs in the presence of chlorophyll, light energy, and enzymes.
4. The chemical equation for glucose is C6H12O6.
5. The balanced equation for phtosynthesis is:
   6CO₂ + 6H₂O----------C₆H₁₂O₆ + 6O₂

2.55 Rate of Transpiration

1. Transpiration is the loss of water through the leaf. It is caused by the heat from the sun. The water turns into gas and diffuses through the stamatal pores as water vapour.
2. If there's a big difference between concentration gradient for water vapour inside the stomatal pore and outside of it, this makes the rate of transpiration faster whereas if there's a small difference, the rate of transpiration will become slower.
3. Low humidity, high temperature, which would cause more evaporation, high light intensity, which would cause more photosynthesis along with heat, and high winds which would blow away the water vapour, on the outside of the plant would mean a big difference, resulting in fast diffusion.
4. However, if the opposite conditions on the outside, would mean a small difference, resulting in slow diffusion.

2.51 Phloem

1. Photosynthesis occurs which produces glucose. However, glucose is a reducing sugar and is chemically very active therefore cannot be transported.
2. Glucose is then converted to sucrose by the plants. Sucrose is soluble and non reducing which makes it easier to transport.
3. Carbohydrate is transported in the form of sucrose.
4. Amino acids are also transported through sucrose. When the two substances, sucrose and amino acids are put together they form a solution known as 'sap' which travels through a tissue known as the phloem.
5. The transportaion goes down the plant and up to the stems and other vital areas of the plants which are growing.
6. A relevant area to transport this would be from the plant down to the roots where Carbon dioxide would be stored in the form of a 'tuber'. The sap can move in any direction, towards any part of the plant. They can also reverse their direction.
7. Translocation is the name of the process of the movement of sap.
8. The sap moves through a tissue known as phloem. Looking at the stem through a longitudinal perspective, you will see a tubular structure.
9. The connection between phloem cells is that the cell walls have pores in it through which the sap moves.
10. Companion sells are attached to these phloem cells which are metabolically very active, they have more mitochondria. If these cells die, the process of translocation will stop.

2.52 Xylem

1. Minerals are dissolved in the water and therefore taken up through the root system along with the water.
2. Water is taken up by the plant and transported into the leaf or other places such as the terminal bud.
3. The tissue which the solution moves up through, called the xylem.
4. The solution always moves in only one direction that is from the roots upward in the plant.
5. The xylem is below the cambium.
6. When you look at the stem the long way, you can extract the xylem. We find a tubular system which have small lignin rings as additional thickening to the cell wall. The cell wall is around the tube.
7. Water along with the dissolved minerals travel up through these tubes

How are plants adapted for gas exchange

1. The process of gas exchange involve the intake of Carbon dioxide into the leaf and the release of Carbon dioxide out of the leaf.
2. The leaf is very thin, therefore the diffusiong distance for Carbon dioxide and oxygen is very small. This speed up the process as both gases, either way, in or out, diffuse faster.
3. Stomatal pores are formed by two guard cells which open and close the pore. This gives the plant some control over gas exchange.

1. The branching pattern creates a larger surface area for absorbtion of water.
2. The roots branch out in order to find water. Zoomin in on the structure of the roots, you will see hair at the end of the root. These are known as root hairs.
3. Root hairs are epidermal cells (cells on the surface of the root) in which the cell walls have been extended. The root hair is an extension of the cell wall. This too, increases the surface area for the absorbtion of water.
4. More minerals are taken in through active transport into the epidermal cells. This then encourages the water to move up the root hair through oasmosis. This basically means that the water moves from the dilute region to the concentrated region.
5. The concentrated region is built by the uptake of minerals through active transport into the cells.
6. Water then moves through the cortex of the root and to the xylem.

2.21 Mineral uptake in roots

1. Magnesium (Mg2+) is taken up into the roots by active transport from the soil the soil.
2. The magnesium is then send up through the xylem, into the leaves so that they can synthesize and make cholrophyll.
3. Nitrate (NO cubed) is taken up into the roots by active transport from the soil and sent up through the xylem into the leaves so that the leaves can produce amino acids which then produces protein.
4. Occasionally, nitrogen is also used in the formation of DNA in plants.

3.4 Plant Fertilisation

1. A tube begins to grow into the stigma from the pollen grain as they germinate. Pollen tubes only grow completely if the pollens are of the same species.
2. Pollen tubes grow all the way down into the ovule.
3. The male nucleus travels down this tube into the ovule.
4. This causes the pollen nucleus to fertilise with the ovule, producing a zycote and as time progresses the zycote turns into the embryonic plant.
5. The outside of the ovule forms the Testa which is the seedcoat.
6. The joining of the nucleus and ovule also produce cotelydons, which acts as a food storage for the seedlings. It is used until the plant grows its first set of leaves.
7. Then the walls of the ovaries thicken through the help of protein and sugars which the plant provides. The plants put a lot of enrgy into thickening the walls of the ovary. This leads to the growth of fruit from the walls of the ovary, also known as the carpel.

These are the things that occur after the nucleus travels down into the ovule.

objective 2.81 phototrpoism

• 'Photo' refers to light whereas 'tropism' refers to growth in response to the light
• When the plant grows towards the light, this process is considered positive.
• Phototropism takes place in stems.
• When the light hits the tip of the stem from all directions, it grows forwards and upwards
• When the light hits the stem from the side (known as lateral light source) the stem bends towards the light. This is also considered 'positive' as the plant is growing towards the light. The light from the other side causes the plant hormone and compound known as auxin, which causes more growth on the other side, causing the stem to bend towards the other side

2.80 Geotropism

• The word 'geo' refers to gravity and 'tropic' refers to growth response therefore this means growth responses to gravity.
• For instance, if an emryonic root was growing from a seed, it wood grow downwards. This is knows as 'positive' geotripism.
• On the contrary, the embryonic shoot grows upwards towards the surface of the soil. This is known as 'negative' geotropism.
• An experiment involves taking a germinating seed, rotating it anticlockwise.
• We will see that the shoot will grow upwards, showing 'negative' geotropism whereas the embryonic root will grow downards, showing 'positive' geotropism.

3.3a insect pollination

• Pollen has got a structure which contains a male nuclei.
• if pollen is transferred from one plant to the other it is known as cross pollination
• Flowers attract insects through coloured petals, scent, and nectaries/fructose
• Many insects also use pollen itself as a form of protein
• The pollen grains are produced in the anther.
• The stamen is the male part of a flower which is composed of the anther. The anther and the filament form the stamen.
• The filament is a stock which holds the anther
• There are three female parts in a flower:

stigma, onto which the pollen grain falls
style, which connects the stigma to the ovary,
and ovary, where we would find the ovules (eggs)

• The entire female structure in the plant is known as the carpel while the stamen is the male part.

objective 3.3b

• Pollen grain is transferred from anther to stigma through the air by the wind.
• Pollen grain weigh less as they're carried in the air by the wind and it probably has a particular wing feature in order to allow it to move through the air
• Anthers stick out the front of a flower, exposed to the wind.
• Stigmas have a really large surface area and a feather-like structure allowing the pollen grain to get caught in between the strands of the stigma.
• Grass is a type of wind pollinated plant.

• Stimuli are changes in environmet e.g. temperature and light
• Plants have receptors which can detect stimulis, resulting in the growth of the plant
• The process of growth from the stimuli is called 'tropism'
• Tropism that involves light is known as 'phototropism' whereas Tropism that involves gravity is called 'geotropism'
• The link between resceptors and response are the 'plant hormones or 'plant growth regulators'
• auxin is a type of plant hormone