The document discusses the ascent of sap in plants. It defines ascent of sap as the upward movement of water from the root to aerial parts of the plant. It describes experiments like the girdling experiment that showed xylem is responsible for the ascent of sap. It also discusses various theories to explain the mechanism of ascent like the Vital Force Theory, Godlewski Relay Pump Theory, Pulsation Theory, and the Cohesion-Transpiration Pull Theory. The Cohesion-Transpiration Pull Theory, also known as the Suction Force Theory, is now widely accepted as it can explain observations like the development of tension in the water column and rhythmic stem contraction and expansion.

1. TAPASWINI BEHERA
BY:-

2. INTRODUCTION
WHAT IS SAP ??
ASCENT OF SAP
MECHANISM OF ASCENT OF SAP
STRUCTURES INVOLBED IN THE PROCESS
OF ASCENT OF SAP
THEORIES OF ASCENT OF SAP
CONCLUSION

3. SAP IS THE DIUTE
SOLUTION OF WATER
AND
MINERAL IONS ABSORBED
FROM SOIL WHICH
MOVES
UPWARD FROM ROOT TO
VARIOUS PARTS OF PLANTS.

4. What is ASCENT OF SAP ??
The upward movement of water from the root
to aerial parts of the plant body is called
ascent of sap or often called translocation of
water. It is fascinating to understand how
water moves in plants to such great heights
such as 400 ft. or more. For example, trees
like Sequoia semipervians are as tall as 300 to
400 ft. They are the 4000 yrs old and giants
among the tree plants. These plants transport
water through their stem must be incredible.

9. Girdling Experiment

10. The logic of the experiment is to find out which of
the stem structures are involved in the
transportation of sap, it may be cortical tissue,
phloem or xylem elements, using a sharp blade; it
is possible to put an incision in the stem till it
reaches the hard part of the stem. Then a ring
of tissue can be removed which consists of cortex
and phloem, leaving behind the xylem elements
intact. This experiment is to determine which of
the stem components are used in the ascent of
sap. However the removal of cortex and phloem
by girdling experiment does not affect the
movement of sap. Thus it can be concluded that
xylem is alone responsible for the ascent of sap.
GIRDLING EXPERIMENT

17. VITAL FORCE
THEORY
GODLEWSKI RELAY
PUMP THEORY/
CLANBERING THEORY
OPPOSED BY
STRAUS BURGER
PULSATION THEORY
(J.C.BOSE)
SUPPORTED BY
MOLISCH
OTHERS DID NOT
SUPPORED

18. VITAL FORCE THEORY
According to these theories the forces
required for ascent Of sap are generated in
living cells of plants. some of the important
Vital foce theories are GODLEWSKI RELAY
PUMPTHEORY AND
PULSATIONTHEORY.

22. Rubber
connecterPressure
developed

25. COHESION TRANSPIRATION PULL
MECHANISM
This theory was proposed by Dixon and
Jolley,
but in later years, the theory has been
expanded and modified to explain certain
observations that were not explained
before. Among the notable scientists who
supported this concept are Curtis and Clark
(1951), Krammar, Hamel and Levit. This
theory is also called as Suction force theory

26. TENSION

29.  Such forces are
called cohesive
forces; they are
nothing but
hydrogen bonds
between the water
molecules. The
overall strength of
water column in
such narrow xylem
elements has been
estimated to be
many folds higher
than the
transpiration pull
and the gravitational
pull put together.

30. EVIDENCE IN SUPPORT OF COHESION
TRANSPIRATION PULL THEORY
1. Transpiration pull developed in the aerial regions at 50% RH in
the air is more than 1000 bars.
2. Cohesive force that holds the water molecules in a column as
narrow as xylem vessels is very strong and they withstand the opposing
transpiration and gravitational pulls.
3. Because of the opposing forces, tension develops in the water
column. As a result, xylem elements become slightly narrow. This
results in the contraction and expansion of the stem which has been
demonstrated by using dendrometer. The diurnal behavior of rhythmic
contraction and expansion is a good evidence for the water column to
be in tension which the transpiration is rapid or not.
5. The forces that operate cohesion transpiration pull are just
passive forces and no metabolic energy is involved in this phenomenon,
because present the movement of water upwards.