Phloem Flashcards
What does phloem tissue consist of?
Also consists of a number of cells types but cell primary concerned with transport are sieve tube elements
How are the sieve tube elements aligned
End to end and form a continuous row called the SIEVE TUBE
1- they have that xylem don’t
End walls but these are perforated with SIEVE PORES to form SIEVE PLATES
What are cell sieve tube elements
Living cells with cell contents
What happens when they are fully grown
No nuclei and reduced colume of cytoplasm is displaced to side of walls and are few organelles
What do they have that extend between sieve tube elements
Microtubules (they pass through the sieve pores)
What are the microtubules for
Thought to be involved in process of translocation of solutes
Movement of sucrose
What is each dive tube element associated with
Coloslet associated with one or more companion cell
Describe companion cells
Have dense cytoplasm rich in mitochondria and other organelles and have a high metabolic rate
How are companion cells linked to sieve tube elements
By plasmodesmata
What to companion cells act as
Supporting cells carrying out many metabolic activities for highly specialised sieve tube elements, allowing them to be specialised for the transport of organic product through the plant
Ie keeps phloem tunes alive
Cells walls
Have no lignin therefore thin
No lignin as not under tension
What do sieve tube elements carry and name process
Sugar away from the leaves to wherever the plant needs it
Called TRANSLOCATION
What does plasmodesmata allow
Transfer of sucrose form companion to sieve tube
Why do companies have a lot of mitochondria
To produce energy to move sucrose into sieve tube
