Mechanism of plant nutrient absorption by plant root and plant tissue

1. Welcome to My
Presentation

2. B Y – R A Z I A S U L T A N A J E M I M
Mechanism of plant nutrient
absorption by plant root and plant
tissue

3. Nutrients Absorption

4. Mechanisms of Nutrient Uptake
 Prior to absorption, nutrients reach the root by 3
mechanisms:
 Mass flow – movement with the water flow.
Most prominent.
 Diffusion – movement in response to a
concentration gradient. Slow.
 Root interception – root extension. Very
important to find new nutrient sources.

5. Absorption through roots
 Passive Uptake: Some ions such as nitrate, can move
passively through the outer membrane of the root surface
along with water in the transpiration stream.
 Active Uptake: Not well understood, but many nutrients (e.g.,
K+ and H2PO4
-) must somehow bond with an ion-specific
carrier (see Insight: p.270).
 Maintaining an Electrical Balance: As cations are absorbed
H+ is excreted or organic anions are produced. As anions are
absorbed HCO3
- is excreted or compensating cations are
absorbed.

7. Stomatal Absorption:
•Rapid absorption of soluble ions from nutrient
enriched water.
•Used mostly for the immediate correction of
critical nutrient deficiencies.
•Most efficient for the micronutrients. Does not
build soil fertility. Danger of phytotoxic effects
if over applied.
Absorption through leaves

8.  The plasma membranes of root cells control solute
uptake
 A plant can absorb enough water and inorganic ions through
its roots to survive and grow
 Root hairs greatly expand surface area for absorption

9.  Substances enter roots in solution
 Water and solutes can move through the root's epidermis and
cortex by two routes
 Intracellular: via cell interiors, through plasmodesmata
 Extracellular: via cell walls; stopped by Casparian strip
 Plants usually use a combination of both

10.  Water and solutes must cross a plasma membrane to enter the
xylem for transport upward
 Controls solutes that enter xylem

11. LE 32-2b
Dermal tissue system
Key
Ground tissue system
Vascular tissue system
Root hair Epidermis Cortex Phloem
Xylem
Casparian
strip
Endodermis
Casparian stripExtracellular route,
via cell walls;
stopped by
Casparian strip
Root hair
Xylem
Plasmodesmata
Endodermis
Cortex
Intracellular
route, via
cell interiors,
through
plasmodesmata
Epidermis

12.  Transpiration pulls water up xylem vessels
 Xylem sap travels from roots to top of plant through the
tracheids and vessel elements in xylem
 Root pressure can push sap up a few meters
 Most sap is pulled up by the transpiration-cohesion-tension
mechanism
 Transpiration
 Loss of water from plant's aerial parts
 Aided by two properties of water: cohesion, adhesion

13. LE 32-3-3
Water uptake from soil
Root hair
Soil particle
Water
Cohesion and
adhesion in the xylem
Xylem
cells
Cohesion,
by hydrogen
bonding
Water
molecule
Adhesion
Cell
wall
Transpiration
Xylem sap
Mesophyll cells
Air space within leaf
Stoma
Outside air

14.  Guard cells control transpiration
 Plants can lose water through transpiration
 Leaf stomata help plants regulate their water content
Opened and closed by flanking guard cells
 Controlled by movement of H2O and K+
Generally stay open during the day, allowing for entry
of CO2 for photosynthesis
Stay closed at night, conserving water
Respond to cues from sunlight, CO2 level, biological
clock

15. LE 32-4
Stoma Guard cells
Vacuole
K+
Stoma opening Stoma closing

16.  Root hairs take up certain inorganic particles by cation
exchange
 Hairs are in direct contact with water films on soil particles
 Ca2+, Mg2+, K+ adhere tightly to soil particles
 H+ released into soil solution by root hairs displaces them
 Can then be absorbed
 Anions less tightly bound to soil particles
 More readily available, but may leach from soil

17. LE 32-8b
Soil particle surrounded
by film of water
Root hair
Water
Air space

18. LE 32-8c
Clay
particle
Root hair
H+
K+
K+
K+
K+
K+
K+
K+
K+

19.  Thank you!