Plant Transport Flashcards

Question

What are companion cells?

Answer 1

The cells that help to load sucrose into the sieve tubes.

Answer 2

- A layer that separates xylem and phloem - It contains meristem cells

Answer 3

- A strand of conducting vessels in the stem or leaves of a plant, typically with phloem on the outside and xylem on the inside. - it is part of the transport system in dicotyledonous plants. They contain supporting and protective tissues such as collenchyma.

Answer 4

The vascular bundles are in the middle t help the plant withstand the tugging stains that result as the stems and leaves blow in the wind.

Answer 5

Vascular bundles are around the edge to give strength and support

Answer 6

Plants with two seed leaves and a branching pattern of veins in the leaf

Answer 7

A layer of dividing cells, here it is called the pericycle.

Answer 8

Water will move in by osmosis

Answer 9

Water will move out of the cell and becomes plasmolysed as they shrink the cell membrane away from the cell water and therefore can survive this for short periods.

Answer 10

Xylem walls become impregnated with lignin, making the walls waterproof. This kills the cells but strengthens the walls and prevents them from collapsing. The lining thickening forms patterns in the cell wall which may be spiral, annular or reticulate (broken rings). This allows the xylem to stretch/flexibility as the plant grows and enables the stem to bend.

Answer 11

- it is where lignification is not complete - they allow water to move sideways from one vessel to another

Answer 12

It is a chemical that protects plant tissue from attack by herbivores

Answer 13

It packs around xylem vessels, storing food and contains tannin deposits.

Answer 14

- xylem vessels can carry water and mineral ions from the roots to the vert top of the plant because they are made from dead cells aligned end to end to form a continuous column - the tubes are narrow so that the water column does not break easily and capillary action can be effective - bordered pits on he lignified walls allow water to move sideways from one vessel to another - the flow of water is not impeded because there are no cross walls, there are no cell contents,nuclear or cytoplasm, and lignin thickening prevent the walls from collapsing

Answer 15

- The vascular bundle is found in the centre of the roots. There is a central core of xylem, often in the shape of an x, with the phloem found in between the arms of the x. This provides strength to withstand the pulling forces which the roots are exposed to. - around the vascular bundle is a layer of cells called the endodermis. - just inside the endodermis is a layer of meristem cells called the pericycle.

Answer 16

- the vascular bundles are found near the edge of the stem. The xylem is found towards the inside of each vascular bundle and the phloem towards the outside. In between is a layer of cambium which are meristems that divide to produce new xylem and phloem cells.

Answer 17

- the vascular bundles form the midrib and veins of a leaf - within each vein, the xylem is located on top of the phloem.

Answer 18

1. Obtain a stick of celery about 5 cm long 2. Rest the stem horizontally on a white tile and use a blade to cut one end as perpendicular to the length of the stem as possible. 3. Now use the blade to cut very thin perpendicular slices of the celery from the edge you have just cut. 4. Use forceps to gently lift the transverse sections into a small beaker containing tap water and leave to soak for 2 minutes. 5. Use a stage micrometer to calibrate the eyepiece graticule for use with x4 and x10 objective lenses. Make a note of each calibration for later use. 6. Use forceps to gently lift the transverse sections into a watch glass containing toluidine blue and leave them in the stain for 1 minute. 7. Use forceps to gently lift the transverse sections back into tap waters to rinse of the excess stain. 8. Place a transverse sections on a microscope slide. Add a drop of water and a coverslip. Repeat this for your three thinnest transverse sections 9. View under the lowest magnification x4 10. Find the clearest view that shows a variety of structures within the stem and produce a scientific drawing of what you see. Use the graticule and your previously noted x4 objective calibration factor to add a scale bar and work out the magnification of your drawing 11. View under a higher magnification objective lense and find the clearest view that shows one vascular bundle 12. Produce scientific drawing of what you see. Use the graticule and the relevant calibration factor to add a scale bar and work out the magnification of your drawing.

Answer 19

1. Task the remaining celery stem. Just as in step 2 cut a short piece off the end perpendicularly to remove the part that has dried out while you have been working on the transverse sections. 2. Make another perpendicular cut to produce a piece of stem about 2 cm long. 3. Carefully cut the piece of stem in half lengthways i.e. split down the middle. 4. Now use the blade to cut very thin lengthways slices of one of the split halves, starting from the freshly cut inner surface. 5. Use forceps to gently lift the longitudinal sections unto a small beaker containing tap water and leave to soak for 2 minutes. 6. Repeat steps 6 to 12 from the transverse sections method with the longitudinal sections.

Answer 20

Water particles move out of the cell - cell shrinks

Answer 21

Water particles move into the cells

Answer 22

Gaps in the cell wall containing cytoplasm that connects two cells.

Answer 23

- provides support for stems and leaves through turgor pressure - when water evaporates it keeps plants cool - minerals are transported in aqueous solutions - water is needed for photosynthesis

Answer 24

- specialised exchange surfaces for the uptake of water and mineral ions - root hair cells are about 200 - 150 nanometres, this makes them visible to the named eye. - with thousands on each root, they maximise surface area in contact with the soil.

Answer 25

- water and mineral ions are contained within small air spaces - when the roots make contact with the soil water moved into the roots via osmosis - the osmosis occurs because there is a higher concentration of solutes in the plant than inside the soil.

Answer 26

It is a measure of tendency of water molecules to move from one place to another. - water moves from a region of higher water potential to a region of lower water potential. The water potential is zero. In a plant cell. The cytoplasm contains mineral ions and sugars (solutes) that will reduce the water potential. This is becayse there are fewer ‘free’ water molecules available that in pure water. As a result the water potential in plant cells is always negative.

Answer 27

- if you place a plant cell in pure water, it will take up water molecules by osmosis. This is because the water potential in the cell is more negative than the water potential of the water. - water molecules will move down the water potential gradient into the cell. But the cell will not continue to absorb water until it bursts. This is because the cell wall has a strong cellulose cell wall. - once the cell is full of water it is described as being turgid. - the water inside the cell starts to put pressure on the cell wall, called pressure potential. As the pressure builds up, it reduces the influx of water.

Answer 28

- if a plant cell is placed into a salt solution with a very negative water potential, then it will lose water by osmosis occurs this is because the water potential of the cell is less negative than the water potential of the solution, so water moves down the water potential gradient out of the cell. - as water loss continues, the cytoplasm and vacuoles shrink, eventually the cytoplasm in longer pushes against the cell wall, and the cell is no longer turgid. - if water continues to leave the cell the the plasma membrane will lose contact with the wall - this is known as plasmolysis - tissue is now flaccid.

Answer 29

When plant cells are touching each other other, water molecules can pass from one cell to another. The water molecules will move from the cell with the less negative water potential to the cell with the more negative water potential. This is osmosis.

Answer 30

Xylem vessels transport water all around the plant. At the leaves, water leaves the xylem and moves into cells mainly by the apoplast pathway. Water evaporates from the cell walls into the spaces between cells in the leaf. When the stomata opens, water evaporates - diffuses out the leave into the surrounding air. The evaporation of water from a plants surface is called transpiration.

Answer 31

The movement of water from the roots to the leaves is called transportation stream. The mechanisms that move the water include cohesion, tension and adhesion.

Answer 32

- symplast pathway - cell cytoplasm to cell cytoplasm through plasmodesmata - vacuolar pathway - apoplast pathway - between the cells via cell walls

Answer 33

- the cellulose cell walls of plants are fully permeable to water. Water molecules can move freely between the cellulose molecules or even in gaps between the cells. Water can also pass across the cell walls into through the partially permeable plasma membrane into the cell cytoplanst or even into the vacuole. - many plants are joined by special cytoplasmic bridges. These are cell junction at which the cytoplasm of one cell is connected to that of another through a gap in their cell walls. These junctions are referred to as plasmodesmata.

Answer 34

- water passes through spaces in the cell walls and between the cells. It does not pass though the plasma membranes into the cells. This means that the water moved by mass flow rather than by osmosis. Also dissolved mineral ions and salts can be carried with the water. - water moves through the cellulose cell wall and intercellular spaces. - the permeable fibres of cellulose do not resist water flow. - water cannot pass the endodermis by this route because the casparia strip in the endodermis cell wall is impermeable to water due the waterproof band. - so all water must pass the endodermis via the cytoplasm

Answer 35

- the endodermis is hoe to the casparian strip - the casparian strip is a impermeable layer of Suberin - a wavy material - as a result all water in the apoplast pathway is forced into symplast pathways. - the function of the stri is to prevent harmful substances from entering the xylem. - prevents leakage of water from xylem vessels and aids the development of root pressure.

Answer 36

- cohesion and tension help move water up plants, from the roots to the leaves against the force of gravity - water evaporates from the leaves at the top of the xylem - this creates tension which pulls more water into the leaf - water molecules are cohesive so when some are pulled into the leaf others follow. This means the whole column of water in the xylem, from the leaves down to the roots, moves upwards. - water enters the stem through the root cortex cells.

Answer 37

- also responsible for the movement of water. As well as being attracted to each other, water molecules are attracted to the walls of the xylem vessels. This helps water rise up through the xylem vessels.

Answer 38

Root pressure (active process) Transpiration pull (cohesion and tension theory) Capillary action

Answer 39

• Affect of Cyanide – Cyanide stops the mitochondria from working, therefore root pressure decreases • Affect of Temperature – root pressure increases as temperature increases and decreases and temperature decreases, suggesting of an enzyme controlled chemical reaction • Reactant Availability – if oxygen levels or respiratory substrate levels drops, root pressure decreases • Guttation – sap and water will move out of cut stems, suggesting they are actively pumped out not drawn up by transpiration

Answer 40

- Many of the properties of water are due to its ability to form hydrogen bonds. - the slight negative charge on the oxygen atom makes it attract the slightly positive hydrogen atom of another water molecule. - the numerous hydrogen bonds in water make it a very stable structure.

Answer 41

- transpiration describes the movement and loss of water from plants - water enters the leaves and passes into the mesophyll cells by osmosis. - water evaporates from the leaves to form water vapour - this is important to remember - large air spaces between the mesophyll cells allow water Vapor to collect and diffuse through the leaves - as a result of this water collecting duct the water potential rises - trasnpiration is the loss of water from the leaves of a plant. Most of this occurs from the underside of the leaf, where there are many stomata in the epidermis - most plants control their water intake my opening and closing their stomata. This happens when water levels change in the guard cells around each stomata. This occurs either passively by osmosis, or by active transport of solutes. - transpiration rates also vary naturally in response to environmental factors such as temperature and humidity.

Answer 42

- transpiration may be an inevitable consequence of gaseous exchange, but it is also essential for the plant to survive - as water Vapor is lost from the leaf, it must be replaced from below. This draws water up the stem as a transpiration stream. - this movement: transports useful mineral ions up the plant, maintains cell turgidity - supplies water for growth, cell elongation and photosynthesis, supplies water that, as it evaporates, can keep the plant cool on a hot day - more than 95% of water taken up by a plant is lost in transpiration

Answer 43

- water evaporated from the leaves, this decreases the water potential of the air spaces inside the mesophyll - water moves into the air spaces from adjacent cells - water moves out of the xylem into the cells in the leaves - water hydrogen bonds to itself (cohesion)and bond to the walls of the xylem vessel (tension) resulting in capillary action.

Answer 44

- water tends to move from areas of high water concentration to areas of low concentration. This is osmosis. - water also tends to move from areas of high hydrostatic pressure to areas of low hydrostatic pressure. It is also affected by gravity and electrostatic forces, such as those that cause surface tension.

Answer 45

- changes in tree diameter - at high transpiration rates (during the day) diameter decreases due to the tension. At night, during low transpiration rates diameter increases - cut flowers - often they draw air in rather than leaking water out, as water continues to move up the cut stem - broken xylems - broken or cut xylems stop drawing up water as the air drawn in breaks the transpiration stream - cohesion between water molecules.

Answer 46

Solutes are actively transported into the roots of the plant, causing water to enter by osmosis. This increases the hydrostatic pressure in the root, forcing water up the stem.

Answer 47

Turgid - open - water moves into the vacuoles by osmosis - outer wall is more flexible than the inner wall, so to cell bends and opens the stomata Flaccid - closed - water moves out of the vacuoles by osmosis - outer wall is more flexible than the inner wall, so the cell bends back and closes the stomata.

Answer 48

In light, the stomata opens to allow gaseous exchange for photosynthesis. Higher light intensity increases the transportation rate

Answer 49

A higher temperature will increase the rate of transpiration. - it increases the rate of evaporation from cell surfaces so that the water vapour potential in the leaf rises - increase the rate of diffusion through the stomata because the water molecules have more kinetic energy - decreases the relative water Vapor potential in the air, allowing more rapid diffusion of molecules through the leaf.

Answer 50

Higher relative humidity in the air will decrease the rate of water loss. This is because there will be a smaller water vapour potential gradient between the air spaces in the leaf and the air outside.

Answer 51

Air moving outside the leaf will carry water vapour that has just diffused out the leaf. This will maintain a high water vapour potential gradient.

Answer 52

If there is little water in the soil, then the plant cannot replace the water that is lost. If there is sufficient water in the soil, then the stomata close and the leaves wilt.

Answer 53

- leaf surface area - thickness of epidermis and cuticle - stomata frequency - stomata size - stomata position

Answer 54

• Cut a shoot underwater to prevent air from entering the xylem. • Cut it at a slant to increase the surface area available for water uptake. • Assemble the photometer in water and insert the shoot under water, so no air can enter • Remove the apparatus from the water but keep the end of the capillary tube submerged in a beaker of water • Check that the apparatus is watertight and airtight • Dry the leaves, allow time for the shoot to acclimatise and then shut off the tap • Remove the end of the capillary tube from the beaker of water until one air bubble forms, then put the end of the tube back into the water • Record the starting position of the air bubble • Start a stopwatch and record the distance moved by the bubble per unit time, eg. Per hour. The rate of air bubble movement is an estimate of transpiration rate. • Remember only change one variable at a time- all other conditions must be kept the same - use a photometer to measure the water uptake of the plant.

Answer 55

- cutting plant shoot may damage plant - plant has no roots so no resistance to water being pulled up.

Answer 56

- A part of the plants that loads assimilates into the phloem sieve tubes - green leaves and stems - storage organs. E.g. tubers and root taps - food stores in seeds

Answer 57

- A part of the plants that removes assimilates from the phloem sieve tubes - growing roots - active processes in the roots and stem - meristem cells activity dividing - developing stored, e.g. seeds, fruits or storage organs

Answer 58

Translocation is the movement of nutrients around a plant. The term includes the movement of minerals, which can be dissolved in water and transported in the xylem, but usually refers to the transport of sugars, amino acids, and other organic molecules in the phloem. Translocation can occur in either direction in the phloem – it is bidirectional. It is an active process, requiring energy, unlike water transport in the xylem.

Answer 59

• Sucrose is loaded into the sieve tube by an active process. • This involves the energy from ATP in companion cells. • Energy used to actively transport H+ ions out of the companion cells. • This increases their concentration outside the cells and decreases their concentration inside the companion cells= concentration gradient occurs. • Special cotransporter proteins are used to help H+ ions diffuse back into the companion cells- only occurs if the H+ ions are accompanied by sucrose- known as cotransport • This process of cotransport is also referred to as secondary active transport- as it results from the active transport of H+ ions out of the cell and moves the sucrose against its concentration gradient. • As the concentration of sucrose in the companion cell increases, it can diffuse through the plasmodesmata into the sieve tubes.

Answer 60

• Transpiration is vital process in plants • A large tree and move up to 250kg of sucrose around it trunk a year • Assimilates are moved into the phloem by active processes There are two route assimilates are moved into the phloem: • Symplat Route • Apoplast Route

Answer 61

• Assimilates are stored in the vacuoles of cells. • The assimilates are moved through the cytoplasm of mesophyll cells into the sieve tubes across connecting plasmodesmata • This is a largely passive process • The assimilates are moved by changes in water potential of cells

Answer 62

• Assimilates diffuse through the cell wall and inter membrane spaces the apoplast) • When they reach the companion cells they are actively transported across the membrane into sieve cells cytoplasm • Hydrogen ions act as co- transporters and actively move assimilates across the membrane

Answer 63

• Movement of sucrose along the phloem is by mass flow. A solution of sucrose, amino acids and other assimilates flows along the tube. • Solution referred to as SAP and it can be made to flow in either direction- up or down the plant • The direction of the flow is determined by differences in hydrostatic pressure between the two ends of the tube, which produces a pressure gradient. • Water enters the tube at the source, increasing the pressure and it leaves the tube at the sink, reducing pressure- therefore the sap flows from the source to the sink.

Answer 64

• Sucrose entering the sieve-tube element, which makes the water potential inside the sieve tube more negative (lower). • As a result water molecules move into the sieve-tube by osmosis fro the surrounding tissues. This increases the hydrostatic pressure in the sieve tube at the source. • Source- any part of the plant that loads sucrose into the sieve tube. Early spring, could be roots where energy stored as starch is converted to sucrose and moved to other parts of the plant in order to enable growth in the spring. • Source- leaf…..Sugars made during photosynthesis are converted to sucrose and loaded into the phloem sieve tubes.

Answer 65

• A sink- anywhere that removes sucrose from the phloem sieve tubes. • The sucrose could be used for respiration and growth in a meristem, or it could be converted to starch for storage in a root. • Where sucrose is being used in the cells, it can diffuse out of the sieve tube via plasmodesmata. • It may also be removed by active transport. • Removal of sucrose from the sap makes the water potential less negative, so water moves out of the sieve tube into the surrounding cells. • This reduces hydrostatic pressure in the phloem at the sink.

Answer 66

At the Source… • Sugars are actively moved into the sieve cytoplasm, this decreases the water potential • Therefore water moves into the sieve cells by osmosis • This increases the hydrostatic pressure inside the phloem, water moves to decrease this pressure At the Sink… • Assimilates are activity moved or diffuse out of the sieve cells • This increases what potential, so water moves out by osmosis, decreasing hydrostatic pressure

Answer 67

• Water entering the sieve tube at the source increases the hydrostatic pressure. • Water leaving the sieve tube at the sink reduces hydrostatic pressure. • Therefore, a pressure gradient is set up along the sieve tube, and the sap flows from higher pressure to lower pressure. • Direction is determined upon where sucrose is being produced and where it is needed. • Even possible that sap could be flowing in opposite directions in different sieve tubes at the same time. • Sap in one tube is all moving in the same direction- MASS FLOW

Answer 68

A source is any part of a plant that loads sucrose into the sieve tube: - green leaves and stems - storage organs that are unloading at the beginning of a growth period. - food stores in seeds when they germinate

Answer 69

If mitochondria of the companion cells are poisoned, translocation stops. The flow of sugars in the phloem is about 10,000 times faster than it would be by diffusion alone suggesting an active process is driving the mass flow.

Answer 70

The pressure in the phloem is high enough to enable insects such as aphids to feed without the need to suck- they simply pierce the phloem and the sap flows into their mouths.

Plant Transport Flashcards

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