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CHAPTER 35

CHAPTER 35. PLANT STRUCTURE AND GROWTH. 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

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CHAPTER 35

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  1. CHAPTER 35 PLANT STRUCTURE AND GROWTH

  2. 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

  3. MONOCOTS V. DICOTS

  4. 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

  5. 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

  6. 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

  7. MORPHOLOGY OF A FLOWERING PLANT

  8. 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

  9. 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

  10. 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

  11. SIMPLE V. COMPOUND LEAVES

  12. 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)

  13. 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)

  14. 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

  15. 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)

  16. 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, THINNER-WALLED, 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

  17. 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

  18. 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

  19. 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

  20. 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

  21. 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

  22. PRIMARY GROWTH OF A ROOT

  23. ZONE OF CELL DIVISION • LOCATED NEAR THE TIP OF THE ROOT; INCLUDES THE APICAL MERISTEM AND ITS DERIVATIVES, THE PRIMARY MERISTEMS

  24. 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

  25. 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

  26. 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

  27. PRIMARY GROWTH OF SHOOTS • A SHOOT’S APICAL MERISTEM IS A DOME-SHAPED 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

  28. 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

  29. 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

  30. 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

  31. LEAF ANATOMY

  32. 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

  33. 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

  34. MODULAR CONSTRUCTION OF A LEAF

  35. 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

  36. PRODUCTION OF SECONDARY XYLEM AND PHLOEM

  37. 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

  38. SECONDARY GROWTH OF A STEM

  39. 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

  40. ANATOMY OF A TREE TRUNK

  41. 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

  42. VIDEO: SECONDARY GROWTH

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