3.3 Flashcards
What is the need for transport systems in multicellular plants
- larger Plants have a smaller surface area to volume ratio
* high metabolic rate
Herbaceous dicotyledonous plants
Plants with 2 seed leaves and a branching pattern of veins in the leaf
Xylem tissue
Water + soluble mineral ions travel upwards in xylem tissue
Phloem tissue
Assimilates such as sugars travel up or down in the phloem tissue
Xylem + Phloem in root
Xylem in centre surrounded by phloem to provide support for the the root as it pushes through the soil
Xylem + Phloem in stems
Are near the outside to provide a sort of ‘scaffolding’ that reduces bending
Xylem + Phloem in leaf
Make up a network of veins which support the thin leaves
Cells in phloem used for transport
- Sieve tube elements
* Companion cells
What is sieve tube elements
Make up the tubes in phloem tissue that carry sap up and down the plants. The sieve tube elements are separated by sieve plants
What is companion cells
The cells that help to load sucrose into the sieve tubes
How does water travel through a plant
•enters through root hair cells
-water moves from areas of higher water potential to areas of lower water potential
•moves through root into xylem
•up xylem out at leaves
-cohesion and tension and adhesion help water move up plants
transpiration
The loss of water vapour from the aerial parts of a plant, mostly through the stomata in the leaves
Process of transpiration
- water enters leaf thru xylem
- moves by osmosis
- water evaporates from cell walls
- water vapour moves thru diffusion out of the leaf through the open stomata
What is transpiration a consequence of
Gas exchange
Environmental factors that affect transpiration rate
- Light intensity
- temperature
- relative humidity
- air movement (wind)
- water availability
Potometer
A device that can measure the rate of water uptake as a leafy stem transpires
Adaptations of plants to the availability of water in their environment (in water)
Plants adapted to living in water:
Hydrophytes (Water Lilies)
•many large air spaces in leaf to keep afloat + absorb sunlight
•stomata exposed to air to allow gaseous exchange
•leaf stem has many large air spaces-buoyancy + oxygen diffusion
Adaptations of plants to the availability of water in their environment (on land)
Xerophyte (plant adapted to living in dry conditions) (Cacti + Marram grass):
Cacti:
• succulents (store water)
•surface area of leaves reduces to reduced water lost by transpiration
•stem green photosynthesis
•roots widespread
Marram grass:
•leaf rolled longitudinally so Air Trapped inside
•thick waxy cuticle to reduce evaporation
•stomata adapted to avoid loss of water vapour
Translocation
The transport of assimilated throughout a plant
•energy-requiring process transporting assimilates especially sucrose, in the phloem between sources (e.g leaves), and sinks (e.g roots meristem)
Details of active loading and removal at the sink TRANSLOCATION
Active loading: used to move substances into companion cells then sieve tubes against concentration grad
•in companion cell ATP transports H+ out of cell
•more h+ tissue that cell
•h+ binds 2 co-transport protein reenters cells
•sucrose molecules binds 2 protein at same time
•movement of H+ used 2 move sucrose into cell
•sucrose out of companion into sieve same process
What translocation do (sink)
Translocation moves substances from ‘sources’ to ‘sinks’. The source of a substance is where its made (high concentration) the sink is the area where it’s used up (lower concentration)
symplast pathway
the route taken by water as it goes from cell to cell via the cell cytoplasm
apoplast pathway
route by which water travels through the cell walls and in spaces between cells of plant tissue when travelling from roots to xylem and from xylem to leaves
