Samenvatting Plant physiology H2: Transport in plants
Introduction:
First leave of a seed = cotyl
Staimen = male reproduction, pistil = female reproduction
Speed vs distance
o From tip to base, a high
number of cells traversed
while there isn’t much
distance covered
o From base to tip, the
comparison is the same,
but the difference
between distance and
speed is smaller
Slide 6
Intracellular transport
o Very short distance, within 1 cell
o Cytoplasmic streaming = movement of large organelles such as chloroplasts
and mitochondria which is facilitated by the cytoskeleton
o Occurs mainly in cells with large vacuoles
o E.g. Elodea (removes N)
Intercellular transport
o Short distance, between cells
o Apoplast = through cell walls & death xylem vessels not controlled
o Symplast = through interconnected cytoplasm via plasmodesmata (open canal
in membrane connecting cytoplasm of 2 cells) semi controlled
o Transcellular transport = through cell wall, cell membrane & tonoplast
multiple times via specific channels controlled
o Plasmodesmata allows transport of water, solutes
(ions), small mol & prot and RNA
o ER produces vesicles who transport prot,… .
o Desmotubule = ER connection through the
plasmodesmata, like the cytosol
o Central rod = inner ER in the desmotubule
o The number of plasmodesmata can regulate symplastic
transport it can be closed by callose (Ca containing
matrix) which can be induced by SA
, o Protein transport via plasmodesmata Chaperones, myosin/actin, exocytosis
(= from cell to organel) fig. slide 18
o Ion transport via plasmodesmata Membrane transporters like H+ pumps do
this and create membrane potentials (difference electric pot over membrane
or between 2 cells) like that
H+ pump against gradient using ATP
K+ pump Passive transport along gradient
Membrane potential Mimosa pudica! Much faster (protection)
o More plasmodesmata -> more electric potential -> more signal (Azolla!)
o Viral RNA transport via plasmodesmata (and phloem) use of movement &
coat proteins, vaccines don’t work in plants because they don’t make
antibodies
o Cytoskeleton also goes through plasmodesmata which its why the channels
can have different shapes (could lead to blockages)
o No plasmodesmata are present between maternal
tissue and the embryo (only apoplastic transport
possible) to avoid viruses being transferred to the
next generation
Xylem & phloem transport from source to sink
o Long distance, between tissues & organs
o Xylem = Upward transport of water & minerals and
passive transport by transpiration
o Phloem = Bidirectional movement of water, solutes & assimilates and active
transport by ATP
o Part of vascular plants, it is developed by
cambium
o Girdling = Cut away the phloem, xylem is exposed
and stays functional so water can be transported
but nutrients can’t trees will die, beavers use
this technique as well to then flood an area so
those trees will drown and die
o There are symplast-apoplast discontinuities of xylem and phloem like the
endodermis that has (almost) no apoplastic transport
Introduction:
First leave of a seed = cotyl
Staimen = male reproduction, pistil = female reproduction
Speed vs distance
o From tip to base, a high
number of cells traversed
while there isn’t much
distance covered
o From base to tip, the
comparison is the same,
but the difference
between distance and
speed is smaller
Slide 6
Intracellular transport
o Very short distance, within 1 cell
o Cytoplasmic streaming = movement of large organelles such as chloroplasts
and mitochondria which is facilitated by the cytoskeleton
o Occurs mainly in cells with large vacuoles
o E.g. Elodea (removes N)
Intercellular transport
o Short distance, between cells
o Apoplast = through cell walls & death xylem vessels not controlled
o Symplast = through interconnected cytoplasm via plasmodesmata (open canal
in membrane connecting cytoplasm of 2 cells) semi controlled
o Transcellular transport = through cell wall, cell membrane & tonoplast
multiple times via specific channels controlled
o Plasmodesmata allows transport of water, solutes
(ions), small mol & prot and RNA
o ER produces vesicles who transport prot,… .
o Desmotubule = ER connection through the
plasmodesmata, like the cytosol
o Central rod = inner ER in the desmotubule
o The number of plasmodesmata can regulate symplastic
transport it can be closed by callose (Ca containing
matrix) which can be induced by SA
, o Protein transport via plasmodesmata Chaperones, myosin/actin, exocytosis
(= from cell to organel) fig. slide 18
o Ion transport via plasmodesmata Membrane transporters like H+ pumps do
this and create membrane potentials (difference electric pot over membrane
or between 2 cells) like that
H+ pump against gradient using ATP
K+ pump Passive transport along gradient
Membrane potential Mimosa pudica! Much faster (protection)
o More plasmodesmata -> more electric potential -> more signal (Azolla!)
o Viral RNA transport via plasmodesmata (and phloem) use of movement &
coat proteins, vaccines don’t work in plants because they don’t make
antibodies
o Cytoskeleton also goes through plasmodesmata which its why the channels
can have different shapes (could lead to blockages)
o No plasmodesmata are present between maternal
tissue and the embryo (only apoplastic transport
possible) to avoid viruses being transferred to the
next generation
Xylem & phloem transport from source to sink
o Long distance, between tissues & organs
o Xylem = Upward transport of water & minerals and
passive transport by transpiration
o Phloem = Bidirectional movement of water, solutes & assimilates and active
transport by ATP
o Part of vascular plants, it is developed by
cambium
o Girdling = Cut away the phloem, xylem is exposed
and stays functional so water can be transported
but nutrients can’t trees will die, beavers use
this technique as well to then flood an area so
those trees will drown and die
o There are symplast-apoplast discontinuities of xylem and phloem like the
endodermis that has (almost) no apoplastic transport
