Monday, September 05, 2005
BIOLOGY - Transport In Plants
Woody plants
Hard and woody
e.g. trees, maize, rice
Herbaceous plants
Little woody tissue
Annual(e.g.Balsam) biennial (e.g.Carrot) perennial (e.g.Onion)
Dicotyledons................Monocotyledons
Veins in leaves: Netlike..........parallel
Flower parts: Usually in fours or fives....Multiples of threes
Arrangement of primary vascular bundles: Arranged in a ring...scattered
Functions
Xylem
Support plant (due to lignified wall)
To transport water from the roots to the leaves due to hollow nature
Phloem
To transport manufactured food from the leaves to other parts of the plants
Related terms
Xylem
Trachieds: young xylem
Lignin: chemical substance deposited on xylem wall
Phloem
Companion cells: supply energy to sieve cells/tubes
Sieve cells/tubes: cells directly involved in transporting manufactured food
Sieve plates: connection between two sieve cells
STEM
Monocots...Dicots
Scattered vascular bundles...Vascular bundles arranged in a ring
Cambium absent...Cambium present
Pith absent...Pith present
[Cambium: closely stacked cells that are actively dividing]
ROOT
Dicots...Monocots
Alternate xylem and phloem
Pith absent...Pith present
Xylem in center of root...Xylem not in center of root
Special features in the roots
Endodermis: thickened cell walls: speed up water movement into xylem
Piliferous layer: outermost layer with root hair cells
Translocation: the transport of manufactured food substance in plants
Evidences:
1) Ringing expt: phloem at outer layer
2) Aphids: feed on cell sap - analyse sap
3) 14CO2: trace 14C fate
How do water enter plants
-zone of root hairs
-fine tubular outgrowths
surrounding: dilute solution of mineral salts
cell sap: concentrated solution of sugars and salts
water enter into cells by osmosis
water moves from one cell to another, which is more concentrated
(cytoplasm->cell membrane->cellwall->cell wall->cell membrane->cytoplasm)
continues until xylem
*active transport required
Apoplast: movement between the 'free spaces' between cellulose fibres
Symplast: movement between cells cytoplasm (across plasmodesmata)
Adaptations of root hair
1) Long and narrow: increase SA:Volume ratio
2) Cell sap with sugars, salts and AA – concentrated: allows diffusion of water and prevents leakage from plasma membrane
3) Living: respires and provides energy for AT
How does water move through the stem:
Transpiration pull
Capillary action
Root pressure
Transpiration: Loss of water vapour from the aerial parts of a plant
Factors affecting transpiration:
1) Humidity of the air
2) Temperature
3) Wind speed
4) Light: increase light = increase rate of photosynthesis = more stomata openings=faster
Importance of transpiration
1) Removal of latent heat
2) Transpirational Pull
3) Ensure that mesophyll cells are moist: carbon dioxide absorption/photosynthesis
Hard and woody
e.g. trees, maize, rice
Herbaceous plants
Little woody tissue
Annual(e.g.Balsam) biennial (e.g.Carrot) perennial (e.g.Onion)
Dicotyledons................Monocotyledons
Veins in leaves: Netlike..........parallel
Flower parts: Usually in fours or fives....Multiples of threes
Arrangement of primary vascular bundles: Arranged in a ring...scattered
Functions
Xylem
Support plant (due to lignified wall)
To transport water from the roots to the leaves due to hollow nature
Phloem
To transport manufactured food from the leaves to other parts of the plants
Related terms
Xylem
Trachieds: young xylem
Lignin: chemical substance deposited on xylem wall
Phloem
Companion cells: supply energy to sieve cells/tubes
Sieve cells/tubes: cells directly involved in transporting manufactured food
Sieve plates: connection between two sieve cells
STEM
Monocots...Dicots
Scattered vascular bundles...Vascular bundles arranged in a ring
Cambium absent...Cambium present
Pith absent...Pith present
[Cambium: closely stacked cells that are actively dividing]
ROOT
Dicots...Monocots
Alternate xylem and phloem
Pith absent...Pith present
Xylem in center of root...Xylem not in center of root
Special features in the roots
Endodermis: thickened cell walls: speed up water movement into xylem
Piliferous layer: outermost layer with root hair cells
Translocation: the transport of manufactured food substance in plants
Evidences:
1) Ringing expt: phloem at outer layer
2) Aphids: feed on cell sap - analyse sap
3) 14CO2: trace 14C fate
How do water enter plants
-zone of root hairs
-fine tubular outgrowths
surrounding: dilute solution of mineral salts
cell sap: concentrated solution of sugars and salts
water enter into cells by osmosis
water moves from one cell to another, which is more concentrated
(cytoplasm->cell membrane->cellwall->cell wall->cell membrane->cytoplasm)
continues until xylem
*active transport required
Apoplast: movement between the 'free spaces' between cellulose fibres
Symplast: movement between cells cytoplasm (across plasmodesmata)
Adaptations of root hair
1) Long and narrow: increase SA:Volume ratio
2) Cell sap with sugars, salts and AA – concentrated: allows diffusion of water and prevents leakage from plasma membrane
3) Living: respires and provides energy for AT
How does water move through the stem:
Transpiration pull
Capillary action
Root pressure
Transpiration: Loss of water vapour from the aerial parts of a plant
Factors affecting transpiration:
1) Humidity of the air
2) Temperature
3) Wind speed
4) Light: increase light = increase rate of photosynthesis = more stomata openings=faster
Importance of transpiration
1) Removal of latent heat
2) Transpirational Pull
3) Ensure that mesophyll cells are moist: carbon dioxide absorption/photosynthesis
# we mugged! @ 4:34 AM 
