Transport in Plants - Phloem Flashcards
1
Q
what does phloem tissue consist of
A
- sieve tube elements
- companion cells
- parenchyma
- fibres
- sclereids
2
Q
what are the sieve tube elements
A
columns of cells that transport the assimilates
3
Q
what are companion cells
A
linked to the sieve tubes, contain dense cytoplasm and carry out the metabolic reactions required for transport
4
Q
what are parenchyma
A
packing cells
5
Q
what are fibres
A
thick lignin walls, dead, hollow, for support
6
Q
what are sclereids
A
lignified parenchyma for support
7
Q
what is the liquid within sieve tube elements
A
phloem sap - mainly sucrose and ions
8
Q
what do the sieve elements contain (adaptations)
A
- thin layer of cytoplasm
- contain mitochondria and endoplasmic reticulum
- no nucleus or ribosomes
- thin end walls (not lignified)
- end walls are perforated forming sieve plates
9
Q
how wide are sieve elements and how many sides
A
10-15 micrometres
usually 5-6 sided in cross section
10
Q
how are companion cells adapted for their function
A
- linked to sieve elements by many plasmodesmata
- dense cytoplasm with a large nucleus
- more mitochondria and ribosomes than normal and no large permanent vacuole
- infoldings of their cell surface membranes to increase surface area
