9.1 Flashcards
why do plants need a transport system?
- metabolic demands
- size
- SA:V ratio
metabolic demands
many plants dont photosynthesise so they need oxygen and glucose transported to them
size
the size of plants vary
therefore plants need a system which would allow them to transport substances up and down from the roots to the shoots
SA:V ratio
plants have a relatively small SA:V ratio which is not good for diffusion therefore needing a transport system
what is a dicot plant?
make seeds which contain two cotyledons
what is the vascular system?
a series of transport system which run through the stem, root, leaves
what are the transport systems arranged into?
a vascular bundle
vascular bundle in a stem
vascular bundle in a root
vascular bundle in a leaf
what is the xylem?
non-living tissue which transports water and mineral ions and provides support
NO CYTOPLASM
how are xylem tissue protected from herbivores?
surrounded by parenchyma tissue which contains tannin which deters herbivores
what does lignin do for the xylem?
provides strength to xylem wall and prevents the xylem from collapsing from transpiration pressure
xylem has to hold up against strong tension due to water movement
waterproofs the walls allowing for adhesion with water molecules
what are the unlignified parts of the xylem called?
bordered pits
what are bordered pits for?
lateral movement of water out of the xylem
what is the phloem?
living tissue which transports assimilates between sink and source cells
which direction does the flow of assimilates go in the phloem?
upwards and downwards
what are the vessels in the phloem tissue?
sieve tube elements
do phloem cells contain a nucleus?
no
what are sieve plates?
perforated walls between sieve tube cells which allow substances in the phloem to pass through
what are linked to the sieve tube elements?
companion cells
how are companion cells linked to the sieve tube elements?
by plasmodesmata channels
do companion cells have a nucleus?
yes
