Chapter 7 AICE biology Topic 1 Structure of stems, roots, leaves, xylem and phloem

We better pass bro.

Where is the xylem found (in leaves)?

the upper side of the vascular bundle (closest to the upper epidermis)

In stems what are the bundles in which the xylem and phloem are found in?

Vascular bundles

In a stem, how are the vascular bundles arranged?

In a ring! (Xylem in the stem is towards the inside and phloem towards the outside.)

Where is the xylem in roots?

the center, and the phloem is between ‘arms’ of xylem

Label 1 and 2

1 is the xylem and 2 is the phloem

Label 3 and 4

3 is the phloem and 4 is the xylem

Label 5 and 6

5 is phloem and 6 is xylem

What is the xylem responsible for?

the transport of water and mineral salts (and support but mostly the other one)

The phloem is a tissue containing?

Sieve tubes

What is the phloem responsible for?

transport through the plant of organic solutes (like sucrose)

Functions of parenchyma (thinner)

• metabolically active

• food storage

• support

• play an important role in the movement of water and food products in the xylem and phloem

Collenchyma functions (thicker because of extra cellulose)

• Provide extra support (in midrib of leaves and at the corners of square stems)

What is the epidermis

the outer layer of cells covering the body of a plant or animal

function of epidermis?

covered with a cuticle which provides additional protection against loss of water and disease

Characteristic of a monocot leaf is?

parallel veins

Characteristic of a monocot stem?

vascular bundles are scattered

Characteristic of a monocot root?

many spread out roots

Characteristic of a dicot leaf?

Branched veins

Characteristic of a dicot stem?

Vascular bundles are arranged in a ring

Characteristic of a dicot root?

One main root

what are the main organs involved in transport within plants?

• Stems

• Roots

• Leaves

How many transport tissues do plants have and what are they called

2 transport tissues

• Xylem

• Phloem

What does the xylem transport

water and inorganic ions (mineral salts) from roots to the parts above ground. 

True or false:

Can xylem move in more than on direction?

False, xylem can move in only one direction, from roots to the rest of the plant (flow is always upwards)

What does the phloem carry?

 substances made by photosynthesis from the leaves to other areas of the plant.

True or false:

Can phloem move phloem sap in more than on direction?

True! upwards in some sieve tubes and downwards in others

function of xylem vessel elements

• Transport of minerals and water

• support

phloem sieve tube function is?

transport of sucrose / organic solutes

phloem companion cell function?

• loading / unloading of sucrose into or out of phloem sieve element 

• forms a functional unit with sieve element

how thick is the endo and epidermis?

1 cell thick

What is the outer region of stem and roots called

 the cortex (and it is mainly made of parenchyma.)

Collenchyma cells are?

parenchyma cells with thicker walls for more support found around the outside of stems just below the epidermis and in the midrib of leaves

Sclerenchyma cells are? (cap of fibers on vascular bundles)

parenchyma cells with the thickest cell walls

Like xylem, sclerenchyma?

walls contain the strengthening material lignin.

dicot leaf (this card is just to examine the photos)

what does the outside of a vascular bundle contain

caps made of sclerenchyma fibers. 

nothing here just examine the photo

features of Sclerenchyma fibres

• Sclerenchyma fibres are elongated cells with lignified walls that help to support the plant. 

• They are dead cells

• they have no living contents at all.

Parenchyma is made up of:

• thin-walled cells used as packing tissue 

• The cells are very metabolically active and may be used for storage of foods like starch. 

• Support the plant, preventing wilting.

• Air spaces between the cells allow gas exchange. 

• Parenchyma forms the cortex in roots and stems, and the pith in stems.

• Parenchyma contains chloroplasts in leaves, where it is modified to form the palisade and spongy mesophyll.

Collenchyma

• modified form of parenchyma with extra cellulose deposited at the corners of the cells.

• provides extra strength.

• the midrib of leaves contains collenchyma

Mesophyll

• They are specialized for photosynthesis and contain chloroplasts

What are xylem vessels made out of?

elongated cells with no end walls (xylem vessel elements)

True or False:

The cells in the xylem structure are alive

false, they r ded fr like me rn michelle - 1:50 am

The lack of cell contents in xylem allows for? (and lack of end wall)

uninterrupted pathway for water to flow

(Still talking ab xylem) The wider the diameter?

the ore water that can be moved up the xylem vessel

The lignified walls in the xylem provide

support, preventing the vessels from collapsing inwards

The cells are elongated cells joined end to end to form tubes for?

transport

no end walls

so minimal resistance to the flow of water

hollow , no cytoplasm, no contents

more space for greater volume to flow with minimal resistance to flow of water 

lignified (walls) / walls contain(s) lignin A thickened walls R lined with lignin so prevents

collapsing preventing it from bursting

True or false:

Is lignin permeable in water?

False, it is impermeable and does not ddissolve

High-power detail diagram of xylem

Phloem is made up of? (living)

sieve tubes made from cells called sieve tube elements

features of sieve tube element

• a cell found in phloem tissue 

• is a living cell

• NO NUCLEUS 

• No ribosomes

• Contains endoplasmic reticulum and mitochondria

• No vacuoles no tonoplast

• very little cytoplasm

• Non lignified walls

Sieve tubes have only a thin layer of cytoplasm and no nuclei this?

reduces resistance to flow

Relate the structure of phloem sieve tube elements to their function

• elongated cells joined end to end to form long tubes  

• very little cytoplasm, no nucleus, fewer organelles to reduce resistance to flow

• sieve plates have pores, so it is easy for phloem sap to pass from cell to cell 

• sieve plates support the sieve tube elements

• plasmodesmata between sieve tube and companion cell for easy loading and unloading of sucrose

features of a companion cell

• a cell with an Un thickened cellulose wall and dense cytoplasm 

• Nucleus present

• large number of mitochondria and ribosomes 

• metabolically very active

• found in close association with a phloem sieve element to which it is directly linked via many plasmodesmata

Relate the structure of phloem companion cell to their function

• Allow the movement of sucrose  from mesophyll cells/ source cells 

• Many plasmodesmata between companion cell and sieve tube to move sucrose into and out of sieve tubes

• Proton pumps in its cell surface membrane pump hydrogen ions out of cell into cell wall to move sucrose against its concentration into the companion cell

• large number of mitochondria and ribosomes to provide ATP and proteins for sieve tubes