4.10, 4.11 Vascular bundles, and CP6

Compare and contrast the structure of xylem and sclerenchyma tissues (6)

-both made of dead, hollow cells

-both have lignin for strengthening

-sclerenchyma has secondary thickening, so it has more cellulose in the walls than xylem

-xylem has pits for horizontal movement of water, sclerenchyma does not

-xylem for water and mineral ion transport, sclerenchyma for structural support

-xylem has perforated end plates for the mass flow of water, sclerenchyma does not

CP6 method step 2

Use a microtome and a razorblade to cut thin, transverse sections of sunflower stem

CP6 method step 6

View slide under microscope under low magnification, and identify vascular bundles

CP6 method step 7

Complete a biological drawing of one vascular bundle

Explain why mitochondria are found in higher numbers in companion cells than phloem cells (3)

-Mitochondria needed to provide ATP

-For active transport of sugars into/out of the phloem

-Phloem has less mitochondria so there is more space for liquid-filled lumen

Explain how xylem vessels are adapted for the transport of water and mineral ions (4)

-xylem is formed of hollow, dead cells for mass transport of water

-contain pits to allow the transverse movement of water into the leaves

-have perforated end plates to allow upward movement of water

-cell walls have lignin which waterproofs the xylem and prevents it leaking

Phloem sieve tubes have no...

organelles

What is translocation?

the movement of sucrose and organic solutes from sources to sinks in the phloem

How do the properties of water enable it to be transported through xylem?

-water molecules are attracted to each other due to cohesion and form hydrogen bonds

-water molecules form a column of water, so tension from transpiration pulls the whole column up xylem

-water is attracted to xylem walls through adhesion, which helps it move up the vessel

Explain how the properties of water enable glucose to be transported in the phloem of a plant (3)

-water is dipolar

-therefore it can form hydrogen bonds with polar molecules such as glucose

-glucose can therefore be dissolved, with water as the solvent

Explain why mitochondria are required in phloem tissue and companion cells (2)

-mitochondria produce ATP energy by respiration

-ATP is needed for the active transport of sugars in and out of the phloem

What are companion cells?

cells that are adjacent to phloem

CP6 method step 1

calibrate microscope using eyepiece graticule

CP6 method step 3

Place the transverse section of stem onto microscope slide

CP6 method step 4

Add a drop of toludine blue stain and leave for 1 minute

CP6 method step 5

Remove excess stain using a pipette

What are the sources of a plant?

the parts where substances are produced

what are the sinks of a plant?

the parts of the plant where the substances are used, e.g. areas of active growth such as shoot, roots

The phloem sieve tube and the companion cells are connected through...

plasmodesmata

Phloem tubes have ____ to allow substances to move from one cell to the next

sieve plates

What do xylem transport?

water and mineral ions

where to xylem vessels transport substances from?

roots of plant

How are the organelles removed from xylem cells?

autolysis

Phloem sieve tubes have no nucleus, it is instead in...

the companion cell