Mass Transport in plants

Phloem-sap-feeders are passive feeders.

Phloem-sap-feeders do not use their jaw muscles to take up sap from phloem.

Explain why they can take up sap without using their jaw muscles?(3 marks)

1)Contents of phloem vessel pushed into insects mouth by high pressure

2)High pressure in phloem vessel could caused by loading of sugars into phloem in leaf

3)Resulting entry of water by osmosis

A phloem-sap-feeder polymerises some of these sugars into polysaccharides.

Suggest the advantage of this?(2 marks)

1)Polysaccharides are insoluble

2)So do not affect water potential of gut

Each phloem-sap-feeding insect receives a few of these bacteria from its parent.(2 marks)

1)Polysaccharides are insoluble

2)So do not affect water potential of gut

Suggest how this has caused a reduction in genetic diversity of the bacteria?(2 marks)

1)Only a few genes passed on

2)Does not include all alleles

Outline a method by which you could find the area of a plant leaf?

Draw around leaf on graph paper and count squares

Describe how a high pressure is produced in the leaves?(3 marks)

1)Water potential becomes lower

2)Water enters phloem by osmosis

Suggest appropriate units the student should use to compare the distribution of stomata on leaves?

cm squared

The pieces of leaf tissue examined were very thin.

Explain why this was important?(2 marks)

1)Few layers of cells

2)So light can pass through

Other than the distribution of stomata, suggest and explain two xerophytic features the leaves of this plant might have?(2 marks)

1)Waxy cuticle so reduces evaporation

2)Thick waxy layer=increase diffusion distance

3)Needles=reduces surface area to volume ratio

Suggest two reasons why the rate of water uptake by a plant might not be the same as the rate of transpiration?(2 marks)

1)Water used for support

2)Water used in hydrolysis

Describe how the structures of starch and cellulose molecules are related to their functions?(5 marks)

Starch

1)Helical shape=compact

2)Large=cannot cross cell surface membrane

3)Branched so glucose easily released for respiration

Cellulose

1)Long,straight unbranched chains of B glucose

2)Joined by hydrogen bonding

3)Form microfibrils which provides strength

Describe the processes involved in the transport of sugars in plant stems?(5 marks)

1)Sucrose is actively transported into the phloem

2)By transfer cells

3)Lowers water potential in phloem and water enters cell by osmosis

4)Produces high hydrostatic pressure

5)Mass flow towards storage tissue

Give two ways in which the structure of starch is similar to cellulose?(2 marks)

1)Are polysaccharides

2)Contain glucose, hydrogen and Oxygen

3)Contain glycosidic bonds

Give two ways in which the structure of starch is different from cellulose?(2 marks)

Starch

1)Contains alpha glucose

2)1-6 glycosidic bond

3)No macrofibrils

Suggest and explain one other way in which sieve cells are adapted for mass transport?(2 marks)

1)No organelles

2)Resists pressure more easily

suggest and explain one other way in which companion cells are adapted for the transport of sugars between cells?(2 marks)

1)mitochondria release ATP

2)Active transport

The leaves of plants that grow in dry areas usually have a low number of stomata per mm2. Use your knowledge of leaf structure to suggest three other adaptations that the leaves might have that enable the plants to grow well in dry conditions?(3 marks)

1)Thick cuticle

2)Small leaves

3)Hairy leaves

The thickness of the aorta wall changes all the time during each cardiac cycle.

Explain why?(3 marks)

1)Aorta stretches because ventricle pressure increases

2)Aorta wall recoils because ventricle relaxes

3)Maintains smooth flow

Describe how tissue fluid is formed and how it is returned to the circulatory system?(6 marks)

1)Hydrostatic pressure

2)Forces water out

3)Large proteins remain in capillary

4)low water potential in blood

5)Due to plasma proteins

6)water enters blood by osmosis

Explain how the structures of the walls of arteries and arterioles are related to their functions?

1)Elastic tissue stretches under pressure

2)Evens out pressure

3)Muscles contraces changes pressure

4)Epithelium smooth reduces friction

The stomata on the leaves of pine trees are found in pits below the leaf surface. Explain how this helps to reduce water loss?

1)Water vapour accumulates

2)Water potential reduced

Describe and explain the effects of increasing light intensity on the tension in the xylem vessels in the leaves?

1)Tension in xylem greater

2)Increase then levels out

3)Stomata opens more

4)Increased evaporation

5)Water potential of leaf cells become more negative

Explain why it was important to keep the humidity constant during the investigation?

Humidity will affect evaporation

Use information from the graphs, and your knowledge of the cohesion-tension theory of water movement through a plant, to explain why the diameter of the trunk is smallest at midday?

1)Diameter of trunk minimal at midday

2)Stomata open in light=more water loss

3)Water evaporates cause of heat

4)H-bonds between water molecules

5)Adhesion between water molecules and xylem vessels

6)Xylem pulled in by tension

Describe and explain three ways in which the leaves of xerophytic plants may be adapted to reduce water loss?

1)Thick cuticle=impermeable

2)Leaves small=reduce SA

3)Less stomata=reduced SA for water loss

Explain how xylem tissue is adapted for its function?

1)long cells with no end walls

2)no cytoplasm

3)Keeps water in cells

Explain how each of the following is related to the function of xylem tissue.

Xylem tissue contains hollow tubes?

Lignin is present in xylem cell walls?

1)Unrestricted water flow

2)Provides support

Describe how water is moved through a plant according to the cohesion-tension hypothesis?

1)Water evaporates from leaves

2)Reduces water potential in cell

3)Water is drawn out of xylem

4)Creates tension

A stem was cut from a transpiring plant. The cut end of the stem was put into a solution of picric acid, which kills plant cells. The transpiration stream continued. Suggest an explanation for this observation?

Water moves in dead cells