Chapter 9 - Transport in plants Flashcards
Why do plants not need a specialised exchange system for gases
- Low metabolic rate
- Large SA:vol ratio of leaves where gas exchange happens
- There are air spaces between all cells in plants so air can diffuse quickly
Why do plants need a transport system
- So that cells deep within plants tissues can receive nutrients needed for cell processes
- The roots cannot obtain sugar and leaves cannot obtain water
What is the transport system in plants called
Vascular tissue
What does the xylem transport
Water and soluble materials
What does the phloem transport
Sugars
What is mass flow
When everything in the cell travels in the same direction
What are xylem and phloem found together in
Vascular bundles
As well as xylem and phloem, what else can be found in vascular bundles
Sieve-tube elements, Companion cells and vessel elements
What are the characteristics of vascular bundles in the roots
- Vascular bundle is found in the centre
- It has a large central core of Xylem (normally in an X shape)
- Surrounded by a ring of cells called the endodermis which contains a casperian strip made of suberin
- Just inside the endodermis is the pericycle which contains meristem cells that can divide for growth
- All surrounded by a large cortex area
- Outside is covered with root hair cells
Why is this central arrangement beneficial to the root
Provides strength to help withstand the pulling forces to which the roots are exposed
Why are all of the characteristics beneficial for the root
- Gives it a larger SA
- Has a lower water potential than the soil
- Carrier molecules in cell membranes for absorption of ions
What are the characteristics of vascular bundles in the stem
- Vascular bundles are found near the outer edge of the stem
- The xylem is found towards the inside of each vascular bundle with the phloem on the outside
- In between each xylem and phloem is a layer of cambium
- The cambium is a layer of meristem cells that can divide to make a new xylem and phloem
What are the benefits of the arrangement of vascular bundles in the stem
Having them around the edge gives strength and support
What are the characteristics of the vascular bundles in the leaves
- The xylem is on top of the phloem
- The vascular bundles form the midrib and the vein like structures in the leaves
- It has a bundle sheath cell surrounding the xylem and phloem
What is different in dicotyledon leaves as opposed to others
It has a branching structure of veins that get smaller as they branch away form the midrib
What is the xylem made up of
Dead cells
What is the phloem made up of
Living cells
Is the cell wall in xylem thin or thick
Thick
Is the cell wall of the phloem thin or thick
Thin
What is the xylem cell wall made up of
Lignin
What is the phloem cell wall made up of
Cellulose
Are the xylem cell walls permeable or inpermeable
Impermeable
Are the phloem cell walls permeable or impermeable
Permeable
Does the Xylem have cross walls
No, cross walls are absent
