9.1 Transport Systems in Dicotyledonous Plants Flashcards
Why do plants need transport systems?
-Plants have metabolic demand, because hormones, mineral ions, waste products, oxygen and glucose need to constantly be transported
-Plants can be incredibly large, so they need effective transport mediums to move substances both up and down
-Plants overall have a small surface area : volume ratio, so cannot rely on diffusion alone to supply their cells with everything they need
What is a dicotyledonous plant?
A plant that makes seeds containing two cotyledons
What makes a monocot’s vascular bundles different from a dicot’s?
Monocot vascular bundles are random, dicot vascular bundles are in a ring
What are the two types of dicot plants?
Herbaceous and woody
What is a vascular system?
Series of transport vessels running through the stem, roots, and leaves. Made up of xylem and phloem
What is a vascular bundle?
A bundle of transport tissues arranged together.
Describe the patterns of vascular tissue in a dicot leaf.
-The midrib of a leaf is the main vein carrying vascular tissue
-Many small, branching veins spread through the leaf.
Describe the patterns of vascular tissue in a dicot stem.
The vascular bundles are around the edge to give strength and support
Describe the patterns of vascular tissue in a dicot root.
The vascular bundles are in the middle, to help the plant withstand tugging strains.
When viewing a transverse section of a vascular bundle, what is the name of the small tissue between xylem and phloem?
Cambium
What type of cell makes up cambium tissue?
Meristem
Is xylem largely living or non-living tissue?
Non-living
What are the two key functions of xylem?
-Transport of water and mineral ions
-Supporting the plant
Describe the flow of material in xylem.
Up from teh roots, to the shoots and leaves. One way system
What are the 3 key components of xylem?
Xylem vessels, xylem parenchyma, xylem fibres
What are xylem vessels?
Long, hollow structures made by several columns of cells fusing together end to end
What is the purpose of xylem parenchyma?
Packs around the xylem vessels, storing food and tannin deposits
What is tannin?
A bitter chemical that protects plant tissues from attack by herbivores
What are xylem fibres?
Long cells with lignified secondary walls that provide extra mechanical strength, but do not transport water
What is the importance of lignified walls?
-Prevents the wall from collapsing inwards
-Waterproofs the vessels
-Improves adhesion of water molecules
What is the name for the holes in the xylem?
Unlignified/bordered pits
What is the function of unlignified pits?
-Present to allow lateral movement of water (and dissolved minerals) between xylem vessels and living cells in the stem
-Also allows water to bypass blockages
Is phloem tissue living or non-living?
Living
Why are phloem cells alive?
Because the active loading of sucrose requires energy from cells
What are the key roles of phloem tissue?
-Transports glucose in the form of sucrose throughout the plant
-Supplies the cells with sugars and amino acids needed for cellular respiration, and for synthesis of all other useful molecules
Describe the flow of materials in phloem tissue.
Flow of materials in the phloem can go BOTH up and down the plant. Two-way flow.
What are the main transporting vessels of phloem?
Sieve tube elements
What are sieve tube elements in made up of?
Many cells joined end to end to form a long, hollow structure.
Are sieve tubes lignified or unlignified?
Unlignified
How does content flow between sieve tube elements?
In the areas between the cells, the walls become perforated to form sieve plates. These let the phloem contents flow between cells.
How do phloem cells lose their nucleus?
-As the large pores appear in sieve tube cell walls, the vacuole membrane, the nucleus and some of the other organelles break down
-The phloem becomes a tube filled with phloem sap
Why is it important for phloem cells to have no nucleus?
So there is more room for dissolved substances to be transported through the sieve tube elements
What is the name of the type of cell that forms next to phloem?
Companion cells
How are companion cells linked to sieve tube elements?
Through the plasmodesmata (microscopic channels through the cellulose cell walls, linking to the cytoplasm of adjacent cells)
What is the function of the companion cells?
To act as a “life support system” for sieve tube cells, which have lost most of their normal cell functions. They are very active.
What does phloem tissue contain?
Supporting tissues, including fibres and sclereids.
What are sclereids?
Cells with extremely thick cell walls
What is tree girdling?
Removal of the bark from a section of a tree
What might you see when a tree is girdled?
Bulge above the ring, translocation past ring prevented, sucrose accumulates, water moves into area by osmosis
Where is the cambium located?
In the stem, between the xylem and phloem tissue
