Transport In Plants Flashcards
Dicotyledonous plants
2 seed leaves
Branching pattern of veins
vascular tissues distributed throughout plant
xylem and phloem found together in vascular bundles that may also contain other types of tissues that give the bundle strength and help support plant.
Meristem
Layer of dividing cells
Xylem contents travel…
Phloem contents travel…
Up
Up and down
The way the vascular bundle is arranged in a young root…
provides strength to withstand the pulling forces to which roots are exposed
Endodermis in young root
special sheath of cells around the vascular bundle
gets water into xylem vessels
inside is layer of meristem cells called pericycle
In stems of non-woody plants the bundles are….
In in stems of woody plants the bundles are…
separate and discrete
separate in young stems and become continuous ring in older stems.
The way the vascular bundle is arranged in stems…
provides strength, and flexibility for the bending forces of the stem
In stems, between the xylem and phloem is a layer of _______ which is…
cambium
a layer of meristem cells that divide to produce the vascular bundle
In a leaf, the vascular bundle forms…
the midrib and veins, which get smaller as they spread
in veins, the xylem is on top of the phloem
Describe the structure and function of the xylem.
contain:
vessels to carry water/dissolved mineral ions
fibres to support plant
living parenchyma cells which act as packing tissue to separate and support the vessels
How do xylem vessels form?
lignin deposited on the walls makes them waterproof, strengthens vessel walls, and prevents vessel from collapsing, but kills cells, so the end walls and cell contents decay which forms long columns of dead cells with no contents.
Lignin thickening forms….
which…
if ____________ is not complete then….
patterns in cell wall which may be spiral, annular (rings), or reticulate (broken rings)
prevents vessel being too rigid and allows flexibility
lignification
it leaves gaps in the cell wall which form bordered pits that allow water to pass between adjacent vessels and to the rest of the living part of the plant.
How are xylem vessels adapted?
made from dead cells in columns (carry stuff)
narrow tubes (so water column doesn’t break easily and capillary action is effective
bordered pits (water can move sideways)
lignin in spiral/annular/reticulate (xylem can stretch as it grows)
no cross-walls, no cell contents, lignin prevents collapse (so water flow isn’t stopped)
What is capillary action?
ability of fluid to flow in narrow spaces without external forces.
Describe the structure and function of phloem.
contains sieve tubes which are made of sieve tube elements and companion cells
sieve tubes have very thin walls
carries sap (sucrose dissolved in water)
Sieve tube elements?
lined up to form sieve tubes
has little cell contents to allow mass flow of sap
the ends have sieve plates (cross-walls) that have holes in them to allow sap movement
sieve plates keep lumen open and block tube when infected (with callose)
Companion cells?
in between sieve tubes
large nucleus, dense cytoplasm
lots mitochondria (ATP for active processes)
help load sucrose actively into sieve tubes
What are the cytoplasmic bridges/cell junctions/gaps in cell walls that plant cells’ cytoplasms are joined by?
Plasmodesmata
plasmodesma : singular
Apoplast pathway?
water passes through cell walls and between cells by mass flow not osmosis
Symplast pathway?
water passes through cell cytoplasm, plasma membrane and plasmodesmata
Vascuolar pathway?
water passes through cytoplasm and vacuoles