Plants

What are the factors that determine if a plant tissue can photosynthesis?

If it is exposed to air, and exposed to sunlight.

What part of pant organisms are the main site of photosynthesis?

The leaves

What is the structure of the layers of leaf tissues adaptated to?

Maximum light absorption and efficient gas exchage

Name the adaptations of a leaf

1. They have a large surface area to allow maximum sunlight absorption and a larger area for gases to enter the tissue for gaseous exchange. Which are both processes that contribute to photosynthesis.

2. They have a thin, flat structure which makes the gases have a shorter diffusion pathway to enter and exit the leafy tissues.

Where are vascular tissues located in a leaf?

The midrib and veins.

What are the two main vascular tissues that are apart of transporting systems inside a plant?

Xylem vessels and pholem vessels

What are the layers of tissue within a leaf?

The cuticle, upper epidermis, palisade mesophyll, spongy mesophyll and the lower epidermis

What role do xylem vessels play in transpiration?

They transport water and mineral ions from roots up to leave tissues.

What role do phloem vessels play in transportation?

They transport dissolved sugars around the plant.

How does the cuticle tissue layer contribute to plants being adapted for maximum light absorption, efficient gaseous exchange or preventing water loss?

It contributes to the prevention of wate loss, as its surface is very waxy which prevents evapouration because wax is a non-polar substance whilst water is. This means that as polar substances dissolve other polar substances, the wax creates a strong physical barrier that closes any gaps between the upper epidermis cells- which would otherwise lead to water vapour escaping- therefore preventing water loss.

How does the upper epidermis tissue layer contribute to plants being adapted for maximum light absorption, efficient gaseous exchange or preventing water loss?

This layer mainly contributes to maximum light absorption, although also has a second role of acting as a physical barrier to the leaf to prevent infections and pathogens entering the cells beow this layer that also mildly prevents evapouration- contributing to the prevention of water loss. Although, its main role of contributing the maximum light absorption is achieved as it is a highly transparent layer of tissue, allowing sunlight to reach cells below which contributes to a high rate of photosynthesis.

How does the palisade mesophyll tissue layer contribute to a plants health?

This layer is the main sight of photosynthesis. As this layer is made up of palisade cells tightly compacted with chloroplasts. Palisade cells are column, cylinder shaped plant cells that have a uniquely larger sized permanent vacuole, which pushes chloroplasts closer to the edges of the cells where they can absorb maximum sunlight.Their column structure allows more sunlight to reach these cells. Whilst chloroplasts contain a green substance called chlorophyll that not only makes plant leafs green but also absorbs sunlight. These cells and organelles allow maximum light absorption, as they are positioned in a straight layer below the very transparent upper epidermis.

How does the spongy mesophyll tissue layer contribute to plants being adapted for maximum light absorption, efficient gaseous exchange or preventing water loss?

This tissue layer primarly contributes to efficient gaseous exchange, as its cells are very loosely packed together. Alongside this, cells are coated in a microscopic layer of water molecules which allows gasses to diffuse through their semi-pemerable membranes, and there are many air spaces. All of these features allow gases to move freely inside the spongy mesophyll and makes the cells more accessible- via diffusion- which is important for respiration and photosynthesis to occur.

How does the lower epidermis tissue layer contribute to plants being adapted for maximum light absorption, efficient gaseous exchange or preventing water loss?

On the surface of the lower epidermis, are important pore structures called stomata. These stomata are tiny opening and closing pores that are controlled by guard cells- when the guard cells gain mass, becoming bigger and more turgid they open, but as the guard cells loose mass, become smaller and more flacid they close. The lower epidermis layer is where substances- such as oxygen, carbon dioxide and water- enter via these stomata pores. So when the neighbouring plant cells are turgid, the stomata opens to allow oxygen and carbon dioxide to enter, whilst letting water leave the plant which balances the water volume inside the plant making the plant is no longer turgid.

What are the adaptations of the palisade masophyll leafy tissue layer?

1. It is the main concentration of chloroplasts, which are made up of a green substance called chlorophyll that absorbs sunlight.

2. Palisade cells have a column shaped structure, and are closely packed together. This increases the surface area for light to be absorbed for photosynthesis.

3. This leafy tissue layer is located near the surface of the leaf, and is below the highly transparent upper epidermis.These features allow maximum light absorption, as the transparency of the upper epidermis allows sunlight to reach the large surface area of chloroplasts and palisade cells.

What are the adaptations of the spongy mesophyll leafy tissue layer?

1. The cells located inside this leafy tissue layer are loosely packed together therefore have many air spaces, allowing gases to easily move throughout the entire layer, and making cells more accessible to diffuse in and out of, which means this layer allows very efficient gaseous exchange.

2. Cells within this layer of tissue are coated in a microscopically small layer of water molecules, making them moist. When gases becomes moist by coming into contact with these cells, gases are able to diffuse through plant cells membranes.

Describe the route that water takes when being transported to leafy tissues from the roots.

Water is extracted from soil from roots, then is transported to a circuit of xylem vessels- made up of xylem cells strengthed by lignin (a carbohydrate material)- which then transports water molecules to a large structure called the xylem stem to then be transported around the plant.

What is lignin?

A carbohydrate material that lines xylem cells- specialised cells that make up xylem vessels that have the function of transporting water around a plant organism- to provide support, strength and make the cells more rigid, to allow efficient water transportation.

What are phloem vessels?

Vascular plant tissues that have the function of transporting dissolved sugars- substances the plant uses as food that are sourced from respiration- around the plant organism. These sugars are dissolved in water, so then they can be moist enough to be able to diffuse through cell membranes.

What are the main uses of food substances- such as glucose that is carried in phloem vessels- in a plant?

1. It can transport fast acting food to areas in immediate need of growth.

2. These sugars heavily contribute to the development of seeds.

3. Food substances can be diverted to organs such as bulbs and tubers where food can be stored for later usage.

What are phloem vessels otherwise known as?

Seive tubes- because they contain seive plates that seive out excess water and convert glucose (made from photosynthesis) into startch and celluose.

What is cellulose?

A common organic polymer made up of thousands of glucose molecules linked together (called saccharide) to form a long chain/ polymer (called polysaccharide). It is a tough, fibrous carbohydrate, and is the substance that makes up plant cell wall.

What is starch in plants?

A complex carbohydrate made from glucose, by linking hundreds of glucose molecules together. It allows sugars to be transported via water without dissolving as starch has a stronger intermolecular structure than glucose. It serves as the plants main source of energy, and can be stored in organs for later use, or can be stored in leaves within chloroplasts to allow energy during nigh time when there is no sunlight for photosynthesis to occur.

Define a seive tube in plant organisms

Made up of specialised cells that have no nuclei, these are what are placed on each end of phloem tissue. They have a non-closed end, so ten the cytoplasm from these seive tubes ca connect one cell to another.

Define a companion cell

Specialised plant cells that are what mainly make up the phloem tissue structure, and they contribute to the pholems function of transporting food substances, by supplying energy to phole tissues via photosynthesis. This is required as translocation- the process of transporting food substances around the plant- is an active process as it goes against the concentration gradient- meaning the food substances (such as dissolved sugars like glucose) go from an area of low concentration to an area of high concentration.

What is the balanced symbol equation of photosynthesis?

6CO₂+6H₂O→C₆H₁₂O₆+6O₂

What is the word equation for photosynthesis?

Carbon dioxide + water→Glucose + oxygen

Describe how gases, water and other molecules enter a plant organism

To allow the plant to perform efficient gaseous exchange in the spongy mesophyll leafy tissue layer, the lower epidermis leafy tissue layer is located just below the spongy mesophyll. This contributes to efficient gaseous exchange as gases can diffuse through stomata- pores located on the lower epidermis surface- even when the stomata are closed, which means minimal water can be lost whilst gaseous exchange can still occur. Although water enters via the root system from soil to the plants stem, and can lead to transpiration- a process of water loss.

What to processes allow substances to move around a plant organism?

Diffusion (a passive process- as particles moves with the concentration gradient- where fluid particles move from an area of high concentration to an area of low concentration through a semi-pemerable membrane), osmosis (a passive process- as particles moves with the concentration gradient- where water molecules diffuse through a semi-pemerable membrane from an area of high concentration to an area of low concentration) and active transport (an active process- meaning it requires energy and goes against the concentration gradient- where substances such as glucose, carbon dioxide, oxygen and water diffuse through a semi-pemerable membrane).

What are the factors that affect the rate of diffusion?

1. Temperatures. If the conditions are high in temperature, the thermal energy will be transferred to the kinetic energy stores of the particles therefore they will move faster. Meaning that if temperatures in the conditions of the particles are high then the rate of diffusion will be high. If temperatures of the conditions of the particles are, then less thermal energy from the conditions will be transferred to the kinetic energy stores of the particles, therefore they will move slower meaning the rate of diffusion will be low.

2. The concentration gradient. The concentration gradient is the difference in particles across a distance. In terms of concentration gradient, the rate of diffusion is affected by how big of a difference there is between the number of particles on the outside of a semi-permeable membrane and the inside of a semi-permeable membrane. The bigger the difference the faster the rate of diffusion, the smaller the difference the slower the rate of diffusion.

3. The surface area. If a cell with a semi-permeable membrane has a small surface area- meaning the total area of surface on a 3 dimensional object- particles will have a smaller platform to diffuse into. Therefore, gases, water and other substances (such as glucose) will likely move past it which will lower the rate of diffusion. Although, a bigger surface area means gases, water and other substances are more likely not to move past it and there is more total surface available to diffuse into which will increase the rate of diffusion

Define the transport system in plants

An organ system that is adapted to the function of transporting food substances (such as dissolved sugars and starch), water and mineral ions around an organism.

What are the two main transporting tissues in a plant?

The xylem and the phloem

Define transpiration

A passive process where water is taken from soil by roots, then enters a circuit of xylem vascular tissues to then be transported to leafs causing them to become turgid. To release excess water and become flacid, stomata- pores located on the lower epidermis leafy tissue layer- open and water molecules evaporate out of the leaf until it is flacid. The water vapour is then captured by the roots which makes it a continuous process.

What is the xylem stem?

A network of hallow xylem vessels- that are vascular tissues made up of dead plant cells connected together- and are strengthed by a substances called lignin.

Define translocation

A process that is the transporting of dissolved sugars around a plant organism against the concentration.

What does a plant use glucose for?

Glucose is a sugar molecule that combines with oxygen to create the chemical reaction respiration, and can be converted to starch to the contribute to the building of plant tissues or cellulose- a carbohydrate molecule that is what plant cell walls are made of.

What are seive tube walls made of?

Seive tube elements/ phloem vessels

What is the role of seive tube plates?

Located inside the long network of phloem vessels they are what convert glucose into starch or cellulose.

How do seive tube elements have the energy to complete the process of translocation?

Although they have no nuclei, they are attached to companion cells that control chemical reactions- such as respiration- to supply energy to the seive tube elements.

What is transpiration?

A process of water loss from a plants tissues via evaporation through the stomata on the lower epidermis leafy tissue layer.

How does transpiration occur?

Water is extracted from soil by roots and then is diverted to a network of xylem vessels to then be taken to leafy tissues, as the leaf becomes turgid stomata open and water evaporates through when it opens. Due to water molecules being made of 2 hydrogen atoms and 1 oxygen atom hydrogenlly bonded together, it creates a large cohesion of water that flows to the leaf, causing the stomata pores to stay open and let more water evapourate. Although, this stream of water that leads to transpiration is simultaneously being replenished by water being extracted from the roots.

During transpiration, how much water is actually being used for the leaf to photosynthsise?

5%

What are the benefits of transpiration?

1. The uptake of water diverted into the leaf allows it to undergo photosynthesis, which provides a food source to the plant.

2. When the inevitable water loss- via evaporation through stomata pores on the lower epidermis leafy tissue layer- occurs, it cools the plant down, as typically the water vapour falls back onto the soil, which can be again extracted from roots.

3. The vast stream of transpiration water molecules, when delivered to the leaf, the leaf gains mass and hardens- meaning that it is turgid. Although this causes stomata pores to open and the cycle of water being evaporated and falling back onto the soil then being extracted by roots again occurs, it supports the structure of herbaceous plants (plants that are grown from seeds and don’t have woody stems).

Describe the uptake of water in a plant

The uptake of water is the stream of water that flows through a plant organism via xylem vascular tissues, up the stem and into leafs for photosynthesis to occur- but also causes transpiration (water loss). Beginning at the roots- where water is extracted from soil to begin the uptake of water- root hair cells being extensions of epidermal cells (cells from the epidermis a layer of tissue that coats the outer of a plant) extract water from soil particles. These root hair cells are adapted to their function in terms of their ability to grow between soil particles, maximizing water absorption. Water enters these root hair cells via osmosis, as there is a high concentration of water molecules in the soil and a low concentration of water molecules in the cytoplasm of the root hair cell. Whilst mineral ions enter via diffusion, as again there is a high concentration of mineral ions in the soil, and a low concentration of mineral ions in the cytoplasm of the root hair cell. These then are transported up the stem and into leafs via xylem vascular tissues.

What are the factors that affect the rate transpiration?

1. Temperature. If temperatures are high then the rate of transpiration will increase, as more water molecules will exceed their boiling points and evaporate out of the leafs of a plant via stomata pores. This then decreases the concentration gradient ratio of water molecules inside the leaf and water molecules outside of the leaf. Therefore, due to osmosis being the net movement of water molecules from an area of high concentration to an area of low concentration, move water molecules will diffuse out of the leaf.

2. Humidity. If the atmostpheric moisture levels (humidity) decrease the rate of transpiration increases. This is because it increases the concentration gradient between water molecules inside the leaf and outside of the leaf. The inside has a high concentration, and the outside has a low concentration. Therefore the rate of osmosis increases, meaning more water molecules will diffuse out of the leafs stomata, which means the rate of transpiration will increase.

3. Air movement. If the movement of neighbouring air particles increases, the rate of transpiration increases. This is because water vapour the is emitted from evaporation from stomata pores is removed from the local air at a faster rate. Therefore, increases the concentration gradient between water molecules inside of the leaf (a high concentration of water molecules) and the outside of the leaf (a low concentration of water molecules). Therefore, the rate of osmosis- the movement of water molecules from an area of high concentration, to an area of low concentration- increases meaning more water molecules will evaporate out of the leaf via stomata pores.

4. Light exposure. If a plant organism has a high intensity light exposure then the stomata pores opens more frequently to let byproducts of photosynthesis (oxygen) out of the leaf via diffusion. Simultaneously, this increases the rate of osmosis via the stomata pores from inside the leaf (high concentration area) to outside the leaf (low concentration area) as the stomata open.

Describe the method used to work out the mass lost from transpiration.

.Remove a number of leafs from a bush or tree, and measure the mass of each of them then record the masses.

.Suspend each leaf using a wire or string.

.After about 24 hours, remove the leafs from their suspension and again, measure the mass, and record it again.

.Calculate a mean value for each leaf using the calculation- Mean= (mass of leaf before suspension + mass of leaf after suspension)/2.