Structure and Function of xylem and pholem Flashcards
what is the xylem for?
transport water and mineral ions from root upwards from high to low pressure
what is phloem for?
transport of organic substances made by the plant eg sucrose up and down phloem
where is xylem and phloem held?
in vascular bundle
structure of xylem?
-dead vessel elements to form continuous tube
- thick lignified walls for waterproofing and structural support
-lignin in spiral or circle patterns, pits in lignin allows water move to other cells
adaptions of xylem?
no cytoplasm or end walls for more space for h20 to be transported
multiple tubes (vessels and tracheids)
structure phloem?
- companion cells and sieve tube elements
- end to end connected by sieve plates
- cytoplasm of companion and sieve linked by gaps called plasmodesmata allows
molecules to move through
-sieve tube reduced cytoplasm for quick movement sugars
what is special about sieve tube walls?
5/6 sided and thin
how are companion cells specialised?
- many mitochondria for atp for active transport sucrose into sieve tube
- large nucleus
- dense cytoplasm
what is cohesion?
water to water attraction
what is adhesion?
water to xylem sides attraction
what does phloem reduced cytoplasm and no nucleus acheive?
less resistance to flow
efficient transport
more space
what does dead cells end to end for xylem acheive?
hollow
low resistance to flow water
what does xylem narrow tubes achieve?
stops column break
helps capillary action (h20 flow - cohesion adhesion)
what doe pits in lignin in xylem do?
sideways flow water and mineral ions
what does spiral/circular lignin do?
structural support
allow growth
flexibility
