Transport Systems In Dicotyledonous Plants Flashcards
what is the pressure in the phloem?
2000kPa
why do multicellular plants need transport systems?
- metabolic demands
- size
- surface area:volume ratio
what are dicotyledonous plants?
plants that make seeds containing two cotyledons.
what are cotyledons?
organs that act as food stores for the developing embryo plant and form the first leaves when the seed germinates.
what are herbaceous dicots?
dicot plants with soft tissues and a relatively short life cycle.
what is a vascular system?
the transport vessels running through the stem, roots and leaves.
what are the two main transport vessels in herbaceous dicots?
the xylem and the phloem.
where are the vascular bundles in the stem?
around the edge of the stem for strength and support.
where are the vascular bundles in the roots?
in the middle to help the plant withstand the tugging strains that result as leaves and stem moves in the wind.
where are the vascular bundles in the leaf?
the midrib. helps support leaf structure.
what is the function of the xylem?
- the transport of water and mineral ions.
- support.
what is the function of the xylem?
- the transport of water and mineral ions.
- support.
is xylem dead or alive?
dead.
what is the direction of travel in the xylem?
from the roots to the shoots and leaves.
what are xylem vessels like?
- long
- hollow
- made by several columns of cells fusing together end to end.
what are the other two tissues associated with xylem?
- xylem parenchyma.
- xylem fibres.
what do thicked wall xylem parenchyma do?
- packs around xylem vessels.
- stores food.
- contains tannin deposits.
what is Tannin?
tannin is found in parenchyma tissue. it is a bitter, astringent-tasting chemical that protects plant tissues from attacking herbivores.
what are xylem fibres?
long cells with lignified secondary walls that provide extra mechanical strength but do not transport water.
what are the different ways lignin can be laid down in xylem vessels?
- rings
- spiral
- relatively solid tubes with lots of small unlignified areas called bordered pits.
what are bordered pits?
unlignified areas where water leaves the xylem and moves into the other cells of the plant.
is phloem dead or alive?
living
what is the role of phloem?
transports food in the form of organic solutes around the plant from the leaves where they are made by photosynthesis.
what is the flow of materials in the phloem?
from source to sink. can travel up or down the plant.
what are the main transporting vessels of the phloem?
sieve tube elements.
are phloem tubes lignified?
no
what are the areas between phloem cells called?
the walls become perforated toform sieve plates. They let phloem contents flow through.
what is the vacuole membrane called?
the tonoplast
what happens when large pores appear in cell walls?
the tonoplast, the nucleus, and some other cells break down
do mature phloem cells have a nucleus?
no
what links companion cells to sieve tube elements?
plasmodesmata.
what are plasmodesmata?
microscopic channels through the cellulose cell wall linking the cytoplasm of adjacent cells.
do companion cells maintain their nucelus and organelles?
yes.
what supporting tissues does phloem tissue contain?
fibres and sclereids.
