Transcript primary growth of roots

THE ANGIOSPERM BODY
• A PLANT’S ROOT AND SHOOT SYSTEMS
ARE EVOLUTIONARY ADAPTATIONS TO
LIVING ON LAND
• PLANT MORPHOLOGY - THE STUDY OF
EXTERNAL STRUCTURES OF PLANTS
• PLANT ANATOMY - THE STUDY OF
INTERNAL STRUCTURE OF PLANTS
• ANGIOSPERMS -FLOWERING PLANTS
ARE THE MOST DIVERSE SPECIES,
BROKEN DOWN INTO 2 CATEGORIES:
– MONOCOTS AND DICOTS
MONOCOTS V. DICOTS
THE ROOT SYSTEM
• ROOT STRUCTURE IS WELL ADAPTED TO:
– ANCHOR PLANTS
– ABSORB AND CONDUCT WATER/NUTRIENTS
– STORE FOOD
• THERE ARE TWO MAJOR TYPES OF ROOT
SYSTEMS
• 1) THE TAPROOT SYSTEM (DICOTS)
– ONE LARGE VERTICAL ROOT
2)FIBROUS ROOT SYSTEM (MONOCOTS)
– A MAT OF THREADLIKE ROOTS SPREADS
OUT BELOW THE SOIL SURFACE
WATER ABSORPTION
• ROOT HAIRS - INCREASE THE SURFACE AREA
OF THE ROOT
• ADVENTITIOUS ROOTS- ROOTS ARISING
ABOVE GROUND FROM STEMS OR LEAVES
• ROOT NODULES- CONTAIN SYMBIOTIC
BACTERIA CAPABLE OF CONVERTING
ATMOSPHERIC NITROGEN TO NITROGENOUS
COMPOUNDS THAT THE PLANT CAN USE FOR
THE SYNTHESIS OF PROTEINS AND OTHER
ORGANIC MOLECULES
THE SHOOT SYSTEM
• SHOOT SYSTEMS ARE COMPRISED OF
VEGETATIVE SHOOTS AND FLORAL
SHOOTS
• VEGATIVE SHOOTS CONSIST OF A STEM
AND ATTACHED LEAVES
• FLORAL SHOOTS TERMINATE IN
FLOWERS
MORPHOLOGY OF A FLOWERING PLANT
STEMS
• STEM MORPHOLOGY INCLUDES:
– NODES - POINTS WHERE LEAVES ARE
ATTACHED TO STEMS
– INTERNODES - STEM SEGMENTS BETWEEN
THE NODES
– AXILLARY BUD - AN EMBRYONIC SIDE
SHOOT FOUND IN THE ANGLE FORMED BY
EACH LEAF AND THE STEM; USUALLY
DORMANT
– TERMINAL BUD - THE BUD ON A SHOOT
TIP
GROWTH OF A SHOOT
• GROWTH OF A SHOOT IS USUALLY
CONCENTRATED AT THE APEX OF THE SHOOT
WHERE THE TERMINAL BUD IS LOCATED
• APICAL DOMINANCE-THE PRESENCE OF A
TERMINAL BUD INHIBITS DEVELOPMENT OF
AXILLARY BUD. APPEARS TO BE AN
EVOLUTIONARY ADAPTATION TO INCREASE
EXPOSURE OF PLANT PARTS TO LIGHT BY
CONCENTRATING RESOURCES ON INCREASING
PLANT HEIGHT
LEAVES
• LEAVES ARE THE MAIN PHOTOSYNTHETIC
ORGANS OF THE PLANT
• A LEAF USUALLY EXISTS IN THE SHAPE OF
A FLATTENED BLADE WHICH IS JOINED TO
THE NODE OF A STEM BY A PETIOLE
• LEAVES OF MONOCOTS AND DITCOTS
VARY IN THE ARRANGEMENT OF THEIR
MAJOR VEINS
– MONOCOTS: PARALLEL VEINATION
– DICOTS: MULTI-BRANCHED NETWORK
SIMPLE V. COMPOUND LEAVES
STRUCTURAL ADAPTATIONS OF
PLANTS
• EACH TYPE OF PLANT CELL HAS
STRUCTURAL ADAPTATIONS THAT MAKE
IT POSSIBLE TO PERFORM THAT CELL’S
FUNCTION. SOME ARE COUPLED WITH
SPECIFIC CHARACTERISTICS OF THE
PROTOPLAST (EVERYTHING INSIDE OF
THE CELL WAL)
PARENCHYMA CELLS
• PARENCHYMA CELLS ARE THE LEAST
SPECIALIZED PLANT CELLS(36.10 PIX, LASER
DISK PICTURES)
• PRIMARY WALLS ARE THIN AND FLEXIBLE
• MOST LACK SECONDARY WALLS
• THE PROTOPLAST USUALLY HAS A LARGE
CENTRAL VACUOLE
• THEY FUNCTION IN MAKING AND STORING
ORGANIC PRODUCTS
• MOST MATURE CELLS DO NOT DIVIDE, BUT
RETAIN THE ABILITY TO DIVIDE AND
DIFFERENTIATE INTO OTHER CELL TYPES
UNDER SPECIAL CONDITIONS (E.G. INJURY)
COLLENCHYMA CELLS
• COLLENCHYMA CELLS USUALLY LACK
SECONDARY WALLS
• THE PRIMARY CELL WALL IS THICKER THAN IN
PARENCHYMA CELLS BUT IS OF AN UNEVEN
THICKNESS
• THEY ARE USUALLY GROUPED IN STRANDS OF
CYLINDERS TO SUPPORT YOUNG PARTS OF
PLANTS WITHOUT RESTRAINING GROWTH
• THEY ARE LIVING CELLS WHICH ELONGATE AS
THE STEMS AND LEAVES THEY SUPPORT GROW
SCLERENCHYMA CELLS
• SCLERENCHYMA CELLS FUNCTION IN SUPPORT
• THEY HAVE VERY RIGID, THICK SECONDARY
WALLS STRENGTHENED BY LIGNIN
• MANY LACK PROTOPLASTS AT FUNCTIONAL
MATURITY, SO THEY CANNOT ELONGATE.
• IN FACT, THEY MAY BE DEAD, FUNCTIONING
ONLY IN SUPPORT
• THERE ARE TWO FORMS: FIBERS, AND
SCLERIDS (SHORTER, IRREGULARLY-SHAPED
CELLS)
XYLEM
• XYLEM CONSISTS OF TWO CELL TYPES, BOTH
WITH SECONDARY WALLS AND BOTH DEAD AT
FUNCTIONAL MATURITY
– TRACHEIDS-LONG, THIN, TAPERED CELLS HAVING
LIGNIN-HARDENED SECONDARY WALLS WITH PITS
(THINNER REGIONS WHERE ONLY PRIMARY WALLS
ARE PRESENT)
– VESSEL ELEMENTS- WIDER, SHORTER, THINNERWALLED, AND LESS TAPERED THAN TRACHEIDS
– ARE ALIGNED END TO END
– THE END WALLS ARE PERFORATED, PERMITTING
THE FREE FLOW OF WATER THROUGH LONG CHAINS
OF VESSEL ELEMENTS CALLED XYLEM VESSELS
PHLOEM
• SIEVE-TUBE MEMBERS ARE CHAINS OF PHOEM
CELLS THAT TRANSPORT SUCROSE, OTHER
ORGANIC COMPOUNDS, AND SOME MINERALS
– THE CELLS ARE ALIVE AT FUNCTIONAL MATURITY
– PROTOPLASTS LACK A NUCLEUS, RIBOSOMES, AND A
DISTINCT VACUOLE
• IN ANGIOSPERMS, THE END WALLS OF SIEVE TUBE
MEMBERS ARE CALLED SIEVE PLATES
– THE PORES PROBABLY FACILITATE THE MOVEMENT OF FLUID
BETWEEN CELLS
PLANT CELL ORGANIZATION
• EACH ORGAN OF A PLANT (LEAf, STEM, ROOT)
HAS 3 TISSUE SYSTEMS: DERMAL, VASCULAR,
AND GROUND TISSUE
– DERMAL T.S.- (EPIDERMIS) SINGLE LAYER OF
TIGHTLY PACKED CELLS COVERING AND
PROTENCINT THE YOUNG PARTS OF THE PLANT
– VASCULAR T.S.-THE XYLEM AND PHLOEM THAT
FUNCITONS IN TRANSPORT AND SUPPORT
– GROUND T.S.- PREDOMINANTLY PARENCHYMA,
WITH SOME COLLENCHYMA AND SCLERENCHYMA;
OCCUPIES THE SPACE BETWEEN THE DERMAL AND
VASCULAR SYSTEMS; FUNCTIONS IN
PHOTOSYNTHESIS, STORAGE, AND SUPPORT
PLANT GROWTH
• MERISTEMS GENERATE CELLS FOR NEW ORGANS
THROUGHOUT THE LIFETIME OF A PLANT
• PLANT GROWTH BEGINS WITH GERMINATION OF THE
SEED AND CONTINUES FOR THE LIFESPAN OF THE
PLANTS
• PLANTS DO NOT LIVE INDEFINITELY, THEY HAVE FINITE
LIFE SPANS
• ANNUALS HAVE ONE GROWING SEASON
• PERENNIALS LIVE MANY YEARS
• INDETERMINATE GROWTH = CONTINUED GROWTH AS LONG AS
THE PLANT LIVES (MOST ANIMALS CEASE GROWING AFTER THEY
REACH A CERTAIN SIZE, DETERMINATE GROWTH)
• APICAL MERISTEMS - LOCATED IN ROOT TIPS AND SHOOT BUDS,
SUJPPLY CELLS FOR PLANTS TO GROW IN LENGTH
• LATERAL MERISTEMS - CYLINDERS OF DIVIDING CELLS
EXTENDING ALONG THE LENTHS OF ROOTS AND SHOOTS
PRIMARY GROWTH
• APICAL MERISTEMS EXTEND ROOTS AND
SHOOTS BY GIVING RISE TO THE PRIMARY
PLANT BODY
• PRIMARY GROWTH PRODUCES THE PRIMARY
PLANT BODY, WHICH CONSISTS OF THREE
TISSUE S YSTEMS
• APICAL MERISTEMS ARE RESPONSIBLE FOR
THE PRIMARY GROWTH OF ROOTS AND
SHOOTS
• THE YOUNGEST PORTIONS OF WOODY PLANTS
AND HERBACEOUS PLANTS ARE EXAMPLES OF
PRIMARY PLANT BODIES
PRIMARY GROWTH OF ROOTS
• ROOT GROWTH IS CONCENTRATED NEAR ITS TIPS
AND RESULTS IN ROOTS EXTENDNG THOUGH THE
SOIL
• THE ROOT TIP IS COVERED BY THE A ROOT CAP,
WHICH PROTECTS THE MERISTEM AND SECRETES
A POLYSACCHARIDE COATING THAT LUBRICATES
THE SOIL AHEAD OF THE GROWING ROOT
• THE ROOT TIP CONTAINS 3 ZONES OF CELLS IN
SUCCESSIVE STAGES OF PRIMARY GROWTH
PRIMARY GROWTH OF A ROOT
ZONE OF CELL DIVISION
• LOCATED NEAR THE TIP OF THE ROOT;
INCLUDES THE APICAL MERISTEM AND ITS
DERIVATIVES, THE PRIMARY MERISTEMS
ZONE OF ELONGATION
• IN THIS REGION, CELLS ELONGATE TO AT
LEAST TEN TIMES THEIR ORIGINAL
LENGTH
• THE ELONGATION OF CELLS IN THIS
REGION PUSHES THE ROOT TIP THROUGH
THE SOIL
• CONTINUED GROWTH IS SUSTAINED BY
THE MERISTEM’S CONSTANT ADDITION OF
NEW CELLS TO THE YOUNGEST END OF
THE ELONGATION ZONE
ZONE OF MATURATION
• IS LOCATED FARTHEST FROM THE ROOT
TIP
• REGION WHERE THE NEW CELLS
BECOME SPECIALIZED IN STRUCTURE
AND FUNCTION AND WHERE THE 3
TISSUE SYSTEMS COMPLETE THEIR
DIFFERENTIATION
PRIMARY TISSUES OF
ROOTS
• THE APICAL MERISTEM PRODUCES THREE PRIMARY
MERISTEMS, WHICH IN TURN GIVE RISE TO THE 3
PRIMARY TISSUES OF ROOTS
• PROTODERM- OUTERMOST PRIMARY MERISTEM
• PROCAMBIUM-FORMS A STELE (CENTRAL CYLINDER)
WHERE XYLEM AND PHLOEM DEVELOP
• GROUND MERISTEM-LOCATED BETWEEN THE
PROTODERM AND PROCAMBIUM; IT GIVES RISE TO THE
GROUND TISSUE SYSTEM
– CORTEX: ROOT AREA BETWEEN THE STELE AND EPIDERMIS
– ENDODERMIS-SINGLE-CELL THICK, INNERMOST LAYER OF
THE CORTEX;SELECTIVELY REGULATES PASSAGE OF
SUBSTANCES FROM SOIL TO THE VASCULAR TISSUE OF THE
STELE
– LATERAL ROOTS-MAY SPROUT FROM THE OUTERMOST LAYER
OF THE STELE OF A ROOT
– ****LASERDISK
PRIMARY GROWTH OF SHOOTS
• A SHOOT’S APICAL MERISTEM IS A DOMESHAPED MASS OF DIVIDING CELLS AT THE TIP
OF THE TERMINAL BUD
• FORMS THE PRIMARY MERISTEMS THAT
DIFFERENTIATE INTO THE 3 TISSUE SYSTEMS
• ON THE FLANK OF THE APICAL MERISTEM DOME
ARE LEAF PRIMORDIA WHICH FORM LEAVES
• MERISTEMATIC CELLS LEFT BY THE APICAL
MERISTEM AT THE BASE OF THE LEAF
PRIMORDIA DEVELOP INTO AXIALLARY
SHOOT GROWTH
• MOST SHOOT ELONGATION ACTUALLY OCCURS
DUE TO GROWTH OF SLIGHTLY OLDER
INTERNODES BELOW THE SHOOT APEX
• GROWTH IS A RESULT OF BOTH CELL DIVISION
AND ELONGATION WITHIN THE INTERNODE
• AXILLARY BUDS MAY FORM BRANCHES LATER
IN THE LIFE OF THE PLANT
• BRANCHES ORIGINATE AT THE SURFACE OF
THE SHOOT AND ARE CONNECTED TO THE
VASCUALR SYSTEM WHICH LIES NEAR THE
SURFACE
PRIMARY TISSUES OF STEMS
• THE VASCUALR TISSUE OF THE STEM IS
ORGANIZED INTO STRANDS OF VASCUALR
BUNDLES THAT RUN THE LENGTH OF THE
STEM (LASERDISK)
• THEY CONVERGE AT THE TRANSITION ZONE
(SHOOT >>> ROOT) TO JOIN THE ROOT STELE
• EACH BUNDLE IS SURROUNDED BY GROUND
TISSUE, INCLUDING PITH AND CORTEX
– DICOTS: BUNDLES ARE ARRANGED IN A RING
WITH PITH INSIDE AND CORTEX OUTSIDE
-MONOCOTS: VASCUALR BUNDLES ARE SCATTERED
THROUGHOUT THE GROUND TISSUE OF THE STEM
TISSUE ORGANIZATION OF
LEAVES
• LEAVES ARE CLOACKED BY AN EPIDERMIS OF
TIGHTLY INTERLOCKED CELLS
• IT PROTECTS AGAINST PHYSICAL DAMAGE AND
PATHOGENS
• A WAXY CUTICLE PREVENTS WATER LOSS
• STOMATA-PORES FLANKED BY GUARD CELLS
WHICH REGULATE GAS EXCHANGE WITH THE
SURROUNDING AIR AND PHOTOSYNTHETIC CELLS
INSIDE THE LEAF
• STOMATA ALSO ALLOW TRANSPIRATION (WATER
LOSS FROM PLANT BY EVAPORATION
• STOMATA ARE MORE NUMEROUS ON BOTTOM
SURFACE OF THE LEAF-MINIMIZES WATER LOSS
LEAF ANATOMY
MESOPHYLL
• THE GROUND TISSUE OF A LEAF IS MESOPHYLL
• CONSISTS MAINLY OF PARENCHYMA CELLS
EQUIPPED WITH CHLORPLASTS
• DICOTS USUALLY HAVE 2 DISTINCT REGIONS OF
MESOPHYLL:
– 1) PALISADE PARENCHYMA-ONE OR MORE LAYERS
OF COLUMNAR CELLS OF THE UPPER HALF OF A LEAF
– 2) SPONGY PARENCHYMA- IRREGULARLY SHAPED
CELLS SURROUNDED BY AIR SPACES THOUGH WHICH
OXYGEN AND CARBON DIOXIDE CIRCULATE.
LOCATED IN THE LOWER HALF OF THE LEAR
MODULAR SHOOT
CONSTRUCTION
• SHOOTS ARE CONSTRUCTED OF A SERIES OF
MODULES PRODUCED BY THE SERIAL
DEVELOPMENT OF MODES AND INTERNODES
WITHIN THE SHOOT APEX
• EACH MODULE CONSISTS OF A STEM, ONE OR
MORE LEAVES, AND AN AXILLARY BUD
ASSOCIATED WITH EACH LEAF
• ELONGATION OF THE INTERNODE PROVIDES
FOR PRIMARY GROWTH OF THE PLANT
MODULAR CONSTRUCTION OF A LEAF
SECONDARY GROWTH
-LATERAL MERISTEMS ADD GIRTH BY
PRODUCING SECONDARY VASCULAR TISSUE
AND PERIDERM
-A SECONDARY PLANT BODY IS COMPRISED OF
THE SECONDARY TISSUES PRODUCED DURING
GROWTH IN DIAMETER
-SECONDARY GROWTH RESULTS FROM TWO
LATERAL MERISTEMS: THE VASCULAR
CAMBIUM AND THE CORK CAMBIUM
VASCULAR CAMBIUM PRODUCES SECONDARY
XYLEM AND PHLOEM
CORK CAMBIUM PRODUCES A TOUGH, THICK
COVERING FOR ROOTS AND STEMS THAT
REPLACES THE EPIDERMIS
PRODUCTION OF SECONDARY XYLEM AND PHLOEM
SECONDARY GROWTH OF
STEMS
• VASCULAR CAMBIUM FORMS WHEN
MERISTEMIC PARENCHYMA CELLS
DEVELOP BETWEEN THE PRIMARY XYLEM
AND PRIMARY PHLOEM OF EACH
VASCULAR BUNDLE AND IN THE RAYS OF
GROUND TISSUE BETWEEN THE BUNDLES
SECONDARY GROWTH OF A STEM
CORK CAMBIUM
• CORK CAMBIUM IS A CYLINDER OF
MERISTEMIC TISSUE THAT FORMS FROM
PROTECTIVE LAYERS OF THE
SECONDARY PLANT BODY
• CORK CAMBIUM IS A CYLINDER OF
FIXED SIZE AND DOES NOT GROW IN
DIAMETER
• LENTICEL = SPONGY REGION IN THE
BARK WHICH PERMIT GAS EXCHANGE
BY LIVING CELLS
ANATOMY OF A TREE TRUNK
SECONDARY GROWTH OF
ROOTS
• VASCULAR CAMBIUM AND CORK CAMBIUM ALSO FUNCTION IN
SECONDARY GROWTH OF ROOTS
• THE VASCULAR CAMBIUM PRODUCES SECONDARY XYLEM TO ITS
INSIDE AND SECONDARY PHLOEM OUTSIDE
• CORK CAMBIUM FORMS FROM THE PERICYCLE OF THE STELE AND
PRODUCES THE PERIDERM, WHICH BECOMES SECONDARY
DERMAL TISSUE
– PERIDERM IS IMPERMEABLE TO WATER, SO THE ROOTS WITH
THE SECONDARY GROWTH FUNCTION TO ANCHOR THE PLANT
AND TRANSPORT WATER AND SOLUTES BETWEEN THE
YOUNGER ROOTS AND THE SHOOT SYSTEM
**OLDER ROOTS BECOME WOODY, AND ANNUAL RINGS APPEAR
IN THE SECONDARY XYLEM
-OLD ROOTS AND OLD STEMS MAY LOOK VERY SIMILAR
VIDEO: SECONDARY GROWTH
QuickTi me™ a nd a Cinep ak decompre ssor are n eede d to see thi s pi ctu re.