3.2 Transport in plants
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word equation for photosynthesis
carbon dioxide + water —–> glucose + oxygen
how many transport systems do plants have
2
what tissue are water and mineral ions transported in
xylem
what tissues are photosynthates transported in
phloem
what are the products of photosynthesis called
photosynthates
what movement does the phloem use
bi-directional
what direction is transport in the xylem
upwards
where in the stem are vascular bundles
the periphery
where in the root are vascular tissues
the centre
explain the uptake of water and minerals ions by the root
minerals are actively transported from soil into root hair cells. This lowers the. water potential in the root hair cells and so water enters by osmosis
why do waterlogged soils struggle with ion uptake
oxygen is required for aerobic respiration to provide ATP for active transport. oxygen can only enter aerated soil
apoplast pathway
the pathway by which water and dissolved mineral ions move through the cell walls by cohesion and adhesion
symplast pathway
the pathway by which water and dissolved mineral ions diffuse through the cytoplasm and plasmodesmata
vacuolar pathway
water can move via the cytoplasm and vacuoles
casparian strip
an impermeable barrier in the endodermis formed from Suberin which blocks the apolast pathway
why does the plant need to control entry of mineral ions into the xylem
selective uptake of mineral ions into the xylem sets up a water potential gradient for water uptake by osmosis
how does the plant ensure toxic ions cannot enter its cells
there are no carrier proteins specific to these ions on the membrane so these ions cannot enter by facilitated diffusion
why do plants need to absorb nitrates from the soil
required for synthesis of amino acids, proteins, DNA, RNA, ATP, nucleotides, nitrogenous bases
why is K+ required
for stomatal opening
why is mg2+ required
constituent of chlorophyll
why is PO43- required
synthesis of phospholipids and a constituent of ATP
what are two adaptations of root hair cells
• large surface area for absorption of water and mineral ions • large amount of mitochondria (ATP required for active transport of ions)
transpiration
the evaporation of water from inside the leaves, through the stomata and into the atmosphere
cohesion
water molecules attracted to each other by hydrogen bonds