Xylem and Phloem Flashcards
Why do multicellular plants need transport systems?
small SA:V ratio
high metabolic rate
a need to move substances to and from individual cells quickly
Diffusion alone would be too slow
What are the two types of tissue involved in plant transport?
Xylem and Phloem
How are xylem adapted for their function?
No end walls = uninterrupted tube
Dead cells = contains no cytoplasm so water can freely move
Lignified walls = aids support, prevents collapse
Pits with no lignin = allows water to move in and out freely
What is the phloem made out of?
Phloem fibres
Phloem parenchyma
Sieve tube elements
Companion cells
What are sieve tube elements and what are its characteristics?
Living cells
forms the tube structure
‘sieve’ part has lots of perforations to allow solutes through
no nucleus
Thin layer of cytoplasm and few organelles
What do the companion cells do?
provide energy to phloem to survive and transport substances
Carry out living functions for themselves and phloem
e.g. provides energy for active transport
