Plant Transport Flashcards
What is the function of sieve tube cells?
To transport organic solutes e.g sucrose and amino acids
Sieve tube cell structure:-
Formed from cells called sieve elements placed end to end. End wall perforated by pores (area called sieve plates). Cytoplasm forms thin layer around periphery + cytoplasmic filaments extend between each sieve cell through the pores.
Where sieve elememts meet = sieve plates
Companion cell function:-
Provide the energy needed to move sucrose into the sieve tube cells.
Companion cell:-
Closely associated with each sieve tube, has dense cytoplasm w/ a large central nuclei, many mitochondria (to produce ATP for active transport of sucrose into phloem) connected to sieve tube by plasmodesmata.
What is translocation?
The transport of soluble organic molecules in plants. Can take place to wherever photosynthesis products are needed.
Phloem structure:-
Living tissue, consists of several cell types. 2 main are sieve tube cells and companion cells. Structural support provided by fibres and parenchyma cells.
Why have plants developed a mass transport system made from columns of plant cells?
They are long and multicellular so diffusion would be too slow to distribute materials.
What is transpiration?
Loss of water from leaves
What are the 2 distinct types of vascular tissue in plants’ mass flow system?
Xylem and Phloem
What do Xylem transport and where?
Water + mineral ions from roots to leaves
What do phloem transport and where?
Sugars and amino acids (made by photosynthesis) from the leaves to the rest of the plant.
How is vascular tissue distributed in the root and why?
Located within central stele. Resists vertical stress (pull) and anchors the plant in the soil.
How is vascular tissue distributed in the stem and why?
Located within separate bundles towards the periphery. Arrangement gives flexible support and resists bending.
T.S section of a stem structure, outside to in:
6
Outer ring= epidermis. Next ring (thick)=cortex. Blobs in this =phloem. Small ring = cambium. Next blobs = xylem. Centre area = pith.
T.S of root outside to in:-
9 (REECEPP CX)
Root hair(coming off). Epidermis (thin outer line). Exodermis (slightly further in thin line). Cortex (large area). Endocyte (next ring). Pericycle (next ring). Phloem (small blobs). Cambium and xylem (star shape).
What are the 2 types of conducting cell in xylem?
Vessels and tracheid.
What two components also found in xylem provide mechanical support?
Fibres and parenchyma cells
How do xylem vessels maintain structure?
Walls of ringed lignin.
Pericycle function:-
Contains vascular tissue (xylem and phloem)
Epidermis function:-
Outer layer of cells, some of which are specialised into root hair cells. Provide increased SA for ion and water uptake.
Root cortex function:-
Made of paremchyma cells, which provide mechanical support to the root.
Endodermis:-
Layer of cells that surround pericycle. Have a Casparian strip around them, made of suberin (waxy substance) that waterproofs the cell walls.
Where do cessels occur?
Angiosperms (flowering plants).
Vessel structure:-
Made of long columns strengthened by lignin.
Lignin:-
Prevents tubes collapsing inwards during transpiration due to negative pressure in the vessels.
What gives the characteristic appearance of vessels under microscopes?
The ringed structure of the ligning.
Vessels impermeable:-
Water and solute can’t pass into xylem cells so protoplasm dies, leaving a hollow tube (lumem) through which water can climb up the plant.
Tracheid structure:-
Elongated cells w/ tapering ends. Strengthened by waterproof lignin.
Where do tracheids occur?
Ferns, conifers + angiosperms but not in mosses.