4 MAJOR PLANT ORGANS (ANGIOSPERMS)
1. LEAF – PHOTOSYNTHESIS
2. STEM – TRANSPORT, SUPPORT OF LEAVES & FLOWERS, STORAGE (STARCH)
3. ROOT – ABSORPTION OF WATER AND MINERALS, ANCHORAGE, STORAGE,
SYNTHESIS OF PROTEINS (RESPIRATION)
4. FLOWER – SEXUAL REPRODUCTION (RESPIRATION)
1.
2.
3.
4.
NUTRIENT
TRANSPRORT SYSTEM:
ORGANIC NUTRIENTS (PHLOEM)
WATER & MINERALS (XYLEM)
GASES
WASTES
CELLS
MECHANISM RESPONSIBLE
1. ORGANIC
NUTRIENTS
(GLUCOSE/
SUCROSE)
PHLOEM – ALIVE
SIEVE TUBES &
COMPANION CELLS
BULK-FLOW HYPOTHESIS (PRESSURE FLOW)
FOLLOWS CONCENTRATION GRADIENT
FROM LEAF  ROOT, STEM, OR FLOWER
COMPANION CELLS  TRANSLOCATION
2. WATER
&
MINERALS
XYLEM – DEAD
VESSEL CELLS &
TRACHEIDS
COHESION-TENSION THEORY (PUSH/PULL)
ROOT  LEAF, STEM, OR FLOWER
3. GASES
LEAF STOMA CONTROLLED BY
GUARD CELLS
WATER EVAPORTAION – TRANSPIRATION
DIFFUSION OF CO2 & H2O IN AND OUT
4. WASTES
ALL CELLS
DIFFUSION – GAS WASTES THRU LEAF
STOMA; SOME WASTES EXCRETED BY ROOT
SYSTEM
LEAF ANATOMY CROSS SECTION
STOMA & GUARD CELLS
COHESION-TENSION THEORY
FACTORS RELATED TO XYLEM TRANSPORT
1. TRANSPIRATION – LOSS OF WATER FROM LEAF DUE TO EVAPORATION (DUE TO CO2
INTAKE).
2. COHESION – ATTRACTION OF “LIKE” MOLECULES; WATER MOLECULES ARE POLAR
(CHARGED)
3. ADHESION – ATTRACTION OF “UNLIKE” MOLECULES – ATTRACTION OF H2O TO
SIDES OF XYLEM CELLS (RESULTS IN CAPILLARY ACTION)
4. ROOT PRESSURE – FORCE EXERTED FROM ROOTS AS A RESULT OF H2O ABSORPTION
(OSMOSIS). ROOT CELLS ARE HYPERTONIC TO SOIL.
5. OSMOSIS – MOVEMENT OF WATER FROM A REGION OF GREATER TO LESSER WATER
CONCENTRATION, THROUGH SEMIPERMEABLE MEMBRANE. ROOT EPIDERMAL CELLS
ARE HYPERTONIC TO SOIL (H2O ENTERS CELLS)
**A CONTINUOUS COLUMN OF H20 IS PRODUCED THROUGHOUT PLANT DUE TO THESE
PHYSICAL FORCES WORKING AT THE SAME TIME
ROOT HAIRS INCREASE SURFACE AREA FOR ABSORPTION. H20 IS PUSHED BY THE
ROOTS, PULLED BY THE LEAVES.
MONOCOT STEMS
DICOT STEMS
MONOCOT PLANTS
1. 1 COTYLEDON (CORN, GRASSES,
SUGAR CANE, BAMBOO)
2. LACK PERMANENT CAMBIUM
3. SCATTERED VASCULAR BUNDLES
4. PARALLEL VEINS (LEAF)
5. FIBROUS ROOT (BRANCHING)
DICOT PLANTS
1. TWO COTYLEDONS (BEAN)
2. PERMANENT CAMBIUM
3. VASCULAR BUNDLES ARRANGED
IN CIRCLE AROUND CAMBIUM
4. NETTED VEINS (LEAF)
5. TAP ROOT (LIKE CARROT)
MOVEMENT OF ORGANIC NUTRIENTS (PHLOEM)
PRESSURE-FLOW OR BULK-FLOW HYPOTHESIS
1. PLANT NUTRIENTS MOVE FROM AN AREA OF GREATER TO LESSER CONCENTRATION
OF THAT NUTRIENT.
LEAF:
GLUCOSE  SUCROSE
(PGAL)
(STORAGE)
2. LEAF REPRESENTS AREA OF HIGHER CONCENTRATION OF GLUCOSE OR SUCROSE.
GLUCOSE FLOWS THROUGH PHLOEM SIEVE TUBE CELLS FROM LEAVES TO OTHER
PLANT ORGANS HAVING LOWER CONCENTRATIONS:
A) STEMS
B) FLOWERS
 CELL RESPIRATION CONSUMES GLUCOSE & CONVERTS
C) ROOTS
IT TO ATP
WHEN LIGHT IS PRESENT,
PHOTOSYNTHESIS IS
GOING ON IN GUARD
CELLS. GUARD CELLS
BECOME HYPERTONIC
TO SURRONDING CELLS
AND TAKE IN H20. THEY
BECOME TURGID (FULL),
WHICH OPENS THE
STOMA. WHEN NO LIGHT,
NO PHOTOSYNTHESIS.
GUARD CELLS COLLAPSE
(FLACID), CLOSE STOMA.