HOW STOMATES OPEN AND CLOSE

    STOMATA OPEN AND CLOSE IN RESPONSE TO ENVIRONMENTAL
    SIGNALS

    LIGHT CAUSES K+ TO ENTER THE GUARD CELLS

    WATER ENTERS VIA OSMOSIS

OSMOSIS REGUIRES:
          A DIFFERENTIALLY PERMEABLE MEMBRANE
          CONCENTRATION GRADIENT

WATER MOVES FROM AN AREA OF HIGH CONCENTRATION TO AN AREA OF LOW CONCENTRATION

    WHEN THE WATER ENTERS THE GUARD CELLS THEY SWELL UP AND
    THE STOMA OPENS

    EACH GUARD CELL HAS SPIRAL THICKENINGS WHICH CAUSE THE
    CELLS TO BOW OUT INSTEAD OF BECOMING FATTER. THESE
    THICKENINGS ARE CALLED RADIAL MYCELLATIONS

    IN DARKNESS, K+ EXITS THE GUARD CELL FOLLOWED BY WATER

VASCULAR TISSUES: XYLEM AND PHLOEM

FUNCTIONS: SPECIALIZED FOR LONG DISTANCE TRANSPORT OF WATER AND DISSOLVED SOLUTES

CONTAIN:

1. TRANSFER CELLS
2. SECRETORY CELLS
3. FIBERS
4. PARENCHYMA CELLS
5. CONDUCTING CELLS

XYLEM -

GREEK FOR XYLOS MEANING WOOD

TRANSPORTS WATER AND DISSOLVED NUTRIENTS FROM THE ROOTS TO ALL PARTS OF THE PLANT

TWO TYPES OF XYLEM
     a. PRIMARY XYLEM
     b. SECONDARY XYLEM

PRIMARY XYLEM:
    DERIVED FROM THE PROCAMBIUM
    HAVE PRIMARY AND SECONDARY WALLS

  a. WALLS SCULPTURED INTO HOOPS, BANDS OR SPRINGS TO ALLOW
     THE GROWING CELLS TO STRETCH

SECONDARY XYLEM FORMED FROM THE VASCULAR CAMBIUM (CALLED WOOD)

CONTAIN SAME CELLS AS PRIMARY XYLEM BUT, IN DIFFERENT
FREQUENCIES.

1. BALSA - LOTS OF PARENCHYMA, FEW VESSELS
2. OAK - LOTS OF FIBERS, FEW PARENCHYMA CELLS

CONDUCTIONG CELLS IN XYLEM

XYLARY ELEMENTS:
     1. TRACHEIDS
     2. VESSEL ELEMENTS

BOTH ARE:
  1. DEAD AT MATURITY
     2. HAVE THICK, LIGNIFIED SECONDARY CELL WALLS
            a. KEEP CELLS FROM COLLAPSING
            b. HELP SUPPORT THE PLANT

TRACHEIDS

1. MOST PRIMITIVE XYLARY ELEMENTS
2. LONG, THIN AND TAPERING
3. HAVE BORDERED PITS FOR SIDE TO SIDE MOVEMENT

VESSEL ELEMENTS

1. MORE ADVANCED THAN TRACHEIDS
2. OCCUR IN ANGIOSPERMS BUT NOT GYMNOSPERMS
3. SHORTER AND FATTER THAN TRACHEIDS

PHLOEM -

GREEK FOR BARK
TRANSPORTS DISSOLVED ORGANIC
MOLECULES THROUGHOUT THE PLANT

PRIMARY AND SECONDARY PHLOEM
          PRIMARY PHLOEM -

    DIFFERENTIATED FROM THE PROCAMBIUM
          HAVE PRIMARY CELL WALLS THAT ARENíT SCULPTED

    SECONDARY PHLOEM -

    DIFFERENTIATED FROM THE VASCULAR CAMBIUM
    MAKES UP THE INNER LAYER OF BARK

CONDUCTING CELLS OF PHLOEM

1. SIEVE ELEMENTS
       a. LACK NUCLEI, ALIVE AT MATURITY
       b. HAVE SIEVE AREAS FOR SIDE TO SIDE MOVEMENT OF WATER
       c. HAVE THIN, PRIMARY CELL WALLS
      d. TWO TYPES OF SIEVE ELEMENTS

  1. SIEVE CELLS - PRIMITIVE, OCCUR IN NONFLOWERING
            PLANTS
     2. SIEVE TUBE MEMBERS - MORE ADVANCED THAN SIEVE CELLS
            SHORTER AND WIDER THAN SIEVE CELLS

    ARRANGED END TO END INTO SIEVE TUBES
          ARE ASSOCIATED WITH COMPANION CELLS

2.  COMPANION CELLS:
         A. ARE ALIVE AT MATURITY
         B. HAVE A NUCLEUS
         C. DIRECT FUNCTIONS OF THE COMPANION CELL
         D. CONNECTED TO SIEVE TUBE BY PLASMADESMATA