THE ANATOMY OF WATER CONDUCTION

WATER AND NUTRIENTS ARE CONDUCTED IN THE VASCULAR TISSUE.

THE VASCULAR TISSUE CONSISTS OF:

   1.   XYLEM

   2.   PHLOEM

XYLEM CONSISTS OF:

   1.   FIBERS -

         STRUCTURE - ELONGATED          CELLS WITH THICK
        
SECONDARY CELL WALLS

         FUNCTION - PROVIDE          STRUCTURAL SUPPORT

   2.    PARENCHYMA CELLS -          STRUCTURE - THIN    
         WALLED

         FUNCTION - STORAGE AND
         LATERAL TRANSLOCATION

    3.   TRACHEARY ELEMENTS

         a.  TRACHEIDS - HIGHLY              SPECIALIZED WATER
             CONDUCTING CELLS             (LONG AND SKINNY)

        b.   VESSEL ELEMENTS -
             LESS SPECIALIZED
             WATER CONDUCTING
             CELLS
           (SHORTER AND FATTER)

BOTH CELL TYPES:

   1.   ARE ELONGATE

   2.   HAVE SCULPTED SECONDARY
        CELL WALLS

   3.   WHEN FUNCTIONAL, FORM A
        NETWORK OF NONLIVING
        CELLS

TRACHEIDS:

   1.   SINGLE CELLS WITH A
        DIAMETER OF 10 TO 50 um
        AND LENGTHS OF LESS
        THAN 1 CM TO 3 CM 

   2.   SECONDARY WALLS 
        COMPOSED OF CELLULOSE,
        HEMICELLULOSE AND  
        LIGNIN

        a. LIGNIN GIVES THE
           CELLS STRENGTH SO
           THEY DO NOT COLLAPSE
           UNDER THE NEGATIVE
           PRESSURE OF A  
          
RISING WATER COLUMN

        b. LIGNIN GIVES THE
           CELLS ADDED SUPPORT

   3.   HAVE PITS IN THEIR
        SIDE WALLS FOR
        TRANSPORT FROM       
       
TRACHEID TO   
        TRACHEID      

        a. PITS THAT ARE
           PAIRED ARE
           “PIT PAIRS”

        b. AREAS WHERE PITS ARE
           LOCATED LACK  
           SECONDARY WALLS

        c. PRIMARY WALL IS               PERFORATED WHERE
           PLASMADESMATA WERE
           LOCATED WHEN THE   
           CELL WAS ALIVE

        d. MAY BE BORDERED DUE
           TO SECONDARY CELL
           WALLS OVERHANGING
           THE PIT AREA

   4.   TRACHEIDS PLACED END 
        TO END OVERLAP AND FORM
        LONG CHAINS OF CELLS

VESSEL ELEMENTS

1.   ARRANGED END TO END

2.   ENDS DISSOLVED AWAY  
     LEAVING PERFORATION PLATES

3.   MORE EVOLUTIONARY ADVANCED 
    
THAN TRACHEIDS

     a. GYMNOSPERMS ONLY HAVE
        TRACHEIDS

     b. ANGIOSPERMS HAVE BOTH
        TRACHEIDS AND VESSELS

THE ASCENT OF SAP

HOW DOES WATER (SAP) GET FROM
THE BOTTOM OF A TALL TREE TO
THE TOP?

   TWO FACTORS:

      1.   TRANSPIRATION

      2.   COHESIVE PROPERTY OF
           H2O

TREES EXIST THAT ARE OVER 100m
TALL.

TO MOVE A VOLUME OF WATER TO THIS HEIGHT A GREAT FORCE IS REQUIRED TO COUNTERACT GRAVITY

RESISTANCES TO WATER MOVEMENT
ALSO EXIST TO INCREASE THIS FORCE. 

   RESISTANCES:

   a. IRREGULAR CELL WALL
      SURFACES

   b. SMALL OPENINGS IN
      PERFORATION PLATES

   c. CELL DEBRIS

THEORIES OF HOW FORCE CAN BE GENERATED

   1.   ROOT PRESSURE

   2.   CAPILLARITY

   3.   COHESION THEORY

ROOT PRESSURE -

   CAN BE SEEN WHEN YOU CUT OFF
   THE TOP OF A PLANT AND
   OBSERVE SAP, OR LIQUID, AT
   THE CUT SURFACE. THIS IS A
   POSITIVE PRESSURE.

    AFFECTED BY:

   1.   STRUCTURE OF ROOTS

   2.   ACTIVE UPTAKE OF
        MINERAL SALTS FROM THE
        SOIL

    HOW?

   1.   STRUCTURE

   2.   MINERAL ION UPTAKE
 
       a. MINERALS DEPOSITED
           IN THE STELE
        b. OSMOTIC POTENTIAL
           LOWERS
        c. WATER MOVES IN
        d. WATER RISES IN THE
           XYLEM
        e. CAN’T BACK OUT
           BECAUSE OF THE
           CASPARIAN STRIP
           IN THE ENDODERMIS
        f. AS MINERAL IONS KEEP
           ENTERING THE STELE,
           WATER WILL KEEP
           FOLLOWING THEM IN

 WATER RISE BY CAPILLARITY

   1.   ADHESION (ATTRACTION OF
        WATER MOLECULES AND
        POLAR GROUPS OF THE
        XYLEM CELL WALL)

   2.   SURFACE TENSION
       (COHESION)

   3.   GRAVITY

THE SMALLER THE TUBE THE HIGHER THE RISE