Phloem Flashcards
Monomers for sieve tube
Sieve elements or sieve cells
How are end walls of sieve elements combined
End walls are perforated forming sieve plates with sieve pores.
Allowing cytoplasmic connections and flow of liquid from one sieve
element to the next.
Describe cells of sieve tube
Cells are alive, with thin cellulose cell walls and
protoplasm.
What happens as the cells mature in sieve tubes
some organelles degenerate
In some plants what does the sieve element contain
fibrous phloem proteins.
What helps facilitate smooth flow of soluble food in sieve tube
narrow layer of cytoplasm containing mitochondria and endoplasmic reticulum at periphery
Where are companion cells found
In angiosperms
adjacent and closely associated with the sieve tube elements.
Characteristics of companion cell
Large nucleus
Dense cytoplasm
Small vacuoles
What links companion cells to sieve elements
plasmodesmata
Describe metabolism of companion cells
Metabolically active
Where are phloem fibres and sclereids found
Occasionally in the primary phloem
More common in the secondary phloem of dicotyledons.
Dicotelydon meaning
Has one cotelydon
Function of Phloem fibres and sclereids
Help to support other phloem cells when the plant is growing
Where is phloem parenchyma found?
Only found in dicotyledonous plant,
Function of phloem parenchyma
In the primary phloem - act as packaging tissues
In secondary phloem - form radial medullary rays
