1. MECHANISM FOR UPTAKE OF
NUTRIENT IN PLANTS
M.Nadeem Ashraf
Soil & Environmental sciences
Faculty of agriculture, Rawalakot

2. Recall
Transport Mechanism
 Passive vs. Active
Plant Transport Tissues
Xylem
 Vessel elements
 Tracheids
Phloem
 Sieve tube member
 Companion cells

3. The apoplastic and symplastic pathways
Apoplast
 Within a plant, the apoplast is
the free diffusional space outside
the plasma membrane. It is
interrupted by the Casparian strip
in roots, air spaces between plant
cells and the cuticula of the plant.
 Structurally, the apoplast is
formed by the continuum of cell
walls of adjacent cells as well as
the extracellular spaces, forming a
tissue level compartment
comparable to the symplast. The
apoplastic route facilitates the
transport of water and solutes
across a tissue or organ.[1] This
process is known as apoplastic
transport.

4. PATHWAYS FOR WATER
UPTAKE
Plasmodesmat
a
 Plasmodesmata
Plasmodesma allow
molecules to travel
between plant cells
through the symplastic
pathway

5. symplast
 The symplast of a plant is the
inner side of the
plasma membrane in which
water (and low-molecular-
weight solutes) can freely
diffuse.
 The plasmodesmata allow the
direct flow of small molecules
such as sugars, amino acids,
and ions between cells. Larger
molecules, including
transcription factors and plant
viruses, can also be transported
through with the help of actin
structures

6. A variety of physical processes
 Are involved in the different types of transport
5 Sugars are produced by
4 Through stomata, leaves photosynthesis in the leaves.
take in CO2 and expel O2. CO2 O2
The CO2 provides carbon for Light
photosynthesis. Some O2
produced by photosynthesis H 2O Sugar
is used in cellular respiration.
3Transpiration, the loss of water
from leaves (mostly through
stomata), creates a force within
leaves that pulls xylem sap upward.
6 Sugars are transported as
phloem sap to roots and other
parts of the plant.
2 Water and minerals are
transported upward from
roots to shoots as xylem sap.
7 Roots exchange gases
1 Roots absorb water with the air spaces of soil,
and dissolved minerals O2 taking in O2 and discharging
from the soil. H 2O CO2. In cellular respiration,
CO2 O2 supports the breakdown
Minerals
of sugars.
Figure 36.2

7. Transport of Xylem Sap
Water Movement in Xylem through TACT
Mechanism;
Four important forces combine to transport water
solutions from the roots, through the xylem
elements, and into the leaves. These TACT forces are:
transpiration
adhesion
cohesion
tension

8. Transport of Xylem Sap
 Transpiration involves the pulling of water up
through the xylem of a plant utilizing the energy of
evaporation and the tensile strength of water. The
previous section describes transpiration more fully.
 Adhesion is the attractive force between water
molecules and other substances. Because both water
and cellulose are polar molecules there is a strong
attraction for water within the hollow capillaries of
the xylem.

9. Transport of Xylem Sap
 Cohesion is the attractive force between molecules of the same
substance..
 Tension can be thought of as a stress placed on an object by a
pulling force. This pulling force is created by the surface tension
which develops in the leaf's air spaces.
A combination of adhesion, cohesion, and surface tension allow
water to climb the walls of small diameter tubes like xylem. This
is called capillary action

10. Root Pressure: A Mechanism to
"Push" Xylem Sap Up the Plant
 At night, transpiration is almost nil. However, the root cells
continue to actively transport minerals into the xylem and the
phloem).
 This active transport lowers the water potential within the stele
 Water passively flows into the roots, pushing the water up
against gravity
 Water that reaches the leaves is often forced out, causing a
beading of water upon the leaf tips known as guttation
 In most plants, however, root pressure is not the primary
mechanism for transporting the xylem
 Tall trees generate

11. The Translocation of Phloem
 Phloem loading results in a high solute concentration at the
source end.
 This creates hypnotic conditions in the phloem, causing water to flow
into the phloem
 Hydrostatic pressure builds in the sieve tube, but it is greatest in the
source
 At the sink, osmosis occurs with the unloading of sugar - water
flows out of the phloem
 The buildup of pressure at the source and the reduction of that
pressure at the sink causes water to flow from source to sink,
carrying the sugar along with it.
 Water is recycled via transport in the xylem