I. root & stem
Root: Stem – vascular bundle: ring at periphery
arrangement resists pulling forces & anchorage in soil arrangement gives flexible support & resists bending
- Xylem: central & star-shaped
- Phloem: between groups of xylem cells
- Cortex: parenchyma cells – mechanical
support
Leaves – vascular bundle: midrib & in veins – flexible strength & resist tearing
J. uptake of water through root hair cells – large SA
- mineral ions: active transport in
- reduce root water potential < soil
- water: osmosis
K. movement of water from epidermis (through cortex) to xylem
apoplast: through spaces in cell walls
symplast: through cytoplasm – plasmodesmata
vacuolar: between vacuoles – in & out through tonoplast + cytoplasm (longer)
L. endodermis casparian strip: impermeable band of waterproof suberin in endodermal cell walls
allows endodermis to regulate water/ion uptake into xylem from soil
blocks apoplast pathway: forces water/ions into cytoplasm = symplast pathway
- water: osmosis
- mineral ions: active transport
water transport into xylem – water potential gradient between endodermis & xylem
Na+ active transported from endodermis to xylem
water into xylem by osmosis
M. xylem: vessels (angiosperms) – transport water & dissolved minerals
- dead (lignin deposition in walls): no contents – large empty lumen = large water volumes + little resistance
- end walls break down – long hollow tube
- pits: allow water to flow laterally between xylem vessels
- lignin rings: waterproof & strengthen walls – prevent vessel collapse under negative pressure
Tracheids (ferns/conifers/angiosperms): strength
Fibres: mechanical support
Parenchyma: packing tissue
Root: Stem – vascular bundle: ring at periphery
arrangement resists pulling forces & anchorage in soil arrangement gives flexible support & resists bending
- Xylem: central & star-shaped
- Phloem: between groups of xylem cells
- Cortex: parenchyma cells – mechanical
support
Leaves – vascular bundle: midrib & in veins – flexible strength & resist tearing
J. uptake of water through root hair cells – large SA
- mineral ions: active transport in
- reduce root water potential < soil
- water: osmosis
K. movement of water from epidermis (through cortex) to xylem
apoplast: through spaces in cell walls
symplast: through cytoplasm – plasmodesmata
vacuolar: between vacuoles – in & out through tonoplast + cytoplasm (longer)
L. endodermis casparian strip: impermeable band of waterproof suberin in endodermal cell walls
allows endodermis to regulate water/ion uptake into xylem from soil
blocks apoplast pathway: forces water/ions into cytoplasm = symplast pathway
- water: osmosis
- mineral ions: active transport
water transport into xylem – water potential gradient between endodermis & xylem
Na+ active transported from endodermis to xylem
water into xylem by osmosis
M. xylem: vessels (angiosperms) – transport water & dissolved minerals
- dead (lignin deposition in walls): no contents – large empty lumen = large water volumes + little resistance
- end walls break down – long hollow tube
- pits: allow water to flow laterally between xylem vessels
- lignin rings: waterproof & strengthen walls – prevent vessel collapse under negative pressure
Tracheids (ferns/conifers/angiosperms): strength
Fibres: mechanical support
Parenchyma: packing tissue
