Water Transport in Plants Flashcards
How do Roots absorb water from soil?
Soil - Plant - Atmosphere
How does water flow thru?
- continuous path
- passive process - no energy expenditure overall
What is involved in water flow?
- different driving forces
- mechanisms of transport
What does soil particles help?
- adsorb and hold water
- compete with plant roots for water
What is matric potential?
in soils, adhesion of water to soil particles
What happens to dry soils?
- remain water cannot be easily absorbed by roots because it is tightly held by the soil particle
- Ψm is negative
- the drier the soil becomes - the more negative the soil becomes
Soil changes
- when soil is at field capacity in wet soil, water pervades all of the channels between soil particles and easily available to roots
- roots absorb water from their immediate environment
- creates air pockets that are ‘refilled’ by water present in nearby larger channels
what happens in extremely dry soils?
- water is tightly bound in smallest channels
- cannot replace water removed by the roots
- large air pockets form
- water is not available to roots
What are continuous in plant tissues?
cell walls
cytosol
What is apoplast?
- continuum of non-living cell walls and extracellular spaces
What is symplast?
- continuum of living cytosol connected by plasmodesmata
Movement of water and soil nurtients start where?
roots
What stimulates root growth?
search for water
what does root growth involve?
- absorption of water & nutrients
- radial transport (water & nutrients)
- vertical transport thru plants
Root hair characteristic
- each root hair is a single cell
Root pathway
- Water enters root hairs by osmosis
- water pass the root, from cell to cell by osmosis; seeps between cells
- water drawn up xylem vessels
what happens when an increase in solute concentration in xylem cells?
cause decrease solute potential compared to cortex
What has a specific carrier proteins which can actively accumulate and concentrate solute inside the root’s vascular cylinder?
Plasmalemma of endodermis
what is endodermis?
- cell layer with Casparian Strip
- cell walls contain suberin
- forms a hydrophobic belt
- separates cortex apoplast from apoplast of root stele
What happens in apoplast?
- water/minerals from soil move into cortex
- movement is passive transport
What happens in Symplast?
- water and minerals may pass from cortex into stele without crossing and membranes only thru symplast because Casparian Strips in endodermis prevent movement in apoplast